4848 Blog 3

WS3B; Dual pattern oscilloscope patterns


Signal Name/s; Injector vs Map sensor
Volt/div/range; Channel A = 20v per div, Channel B = 5v per div
Time/div/range; 20ms per div

           

Explain the operation of the sensors or actuators using the picture;


(use letters at different points, and describe what happens there)

The beginning of the pattern where it shows a straight line is where the injector has supply voltage to it, the transistor triggers a ground circuit, this leads us to point A;

*Point A is the time span that the injector is open for (injecting fuel) at idle the injector will be open for around 2.0ms give or take. By comparing the div time to the time measured we can see that the injector open rate was about 5.0ms, which means the engine is under load as the injector is opened for a longer period of time.

*Point B this is the injectors voltage spike, as the injectors coils magnetic field is collapsed a voltage spike is created and the only way the voltage can escape is for the injector to use it.

*Point C is where the injector recovers supply voltage and the injector is off because there is no ground triggering the injector.

Moving on to the MAP signal;

*Point D shows us the MAP signal as the engine is not under load.


*Point E the engine is starting to come under load, because the MAP signal is getting lower.

*Point F the engine is under high load because the output signal of the MAP is low.



The MAP sensor helps the ECU make the right measurement as to how long the injectors should be opened for, because the MAP sensor senses engine load (vacuum) when the vacuum amount is changed this sends the ECU a signal to let it know that it needs to correspond to this by triggering the right amount of injector spray.



Signal name; Ignition primary vs primary current
Volt/div/range; Channel A = 20v per div, Channel B = 1amp per div
Time/div/range; 10ms per div

Explain the operation of the sensor or actuator using the graph;


(Use arrows at different points, and descibe what happens there)

*Point A; This shows the supply voltage to the coil.


*Point B; This part of the pattern is called the dwell time, this is the amount of time it takes the coil to charge up and fire.

*Point C; Is the collapsation of the magnetic field produced by the coil, thats why the pattern displays a huge voltage spike.

*Point E; shows no reading of current.

*Point F; this displays the signals peak current.

*Point G; the pattern has returned to no current reading.


By looking at both the patterns we can see that they relate to each other directly. If you look at the ignition primary voltage pattern, you can see off, on, firing voltage times peaks etc, if you then look at the current pattern and compare the two you can see that as the coil turns on the current does also, when the coil sends out the peak voltage, the current reading also shoots up to its highest point at the exact same time. 





Signal name; Ignition primary vs Injector
Volt/div/range; Channel A = 20v per div, Channel B = 50v per div
Time/div/range; 10ms

Explain the operation of the sensor or actuator using the graph;

(Use arrows at different points and describe what happens here)

*Point A; Just the same as one of the previous tests, this shows supply voltage to the ECU.


*Point B; Also, again. This part of the pattern shows the amount of time that the injector is open for.

*Point C; Point C is also the same as a previous test. Injector gives a big voltage spike because as the injectors coil is turned off the magnetic field inside the injector is collapsed causing the big voltage spike


*Point D; shows us the supply voltage to the coil,

*Point E; is when the coil has been triggered, this period of time is also known as dwell time.

*Point F; shows the voltage peak of the coil, aswell as a few little coil oscillations at the bottom after the peak.

As you can see by looking at the graph in the picture above, you can see that both patterns correspond with each other. As the injector (top pattern) finishes dwell time and shows firing voltage so does the ignition pattern, there may-be a few micro seconds difference between both firing patterns but thats to be expected. The reason both of these patterns fire at the same time is that the engine is timed so that as the injector sprays, the ignition system sparks the spark plug allowing for combustion. You might be asking why the ignition pattern is more frequent than the injector pattern? This is because the ignition pattern is the over all ignition pattern for the engine, the injector pattern is less frequent because we are only displaying one of the injectors patterns, if all the injectors patterns were displayed we would see that each of the injectors correspond to each of the firing voltages on the ignition pattern.




Signal name; RPM vs Injectors

Volt/div/range; Channel A = 20v per div, Channel B = 10v per div
Time/div/range; 5mS per div

*Point A; Again this pattern is just a basic injector cycle pattern.


*Point B; This is the signal that the inductive type distributor puts out, it is an A/C signal. The reason for this being is that the inductive pick up is made out of magnets, so as the rotor wheels teeth pass the inductive pick up the magnetic field is altered. The magnet has a DC voltage supply to it, but as the field is altered the signal changes into a AC signal.

*Point C; Between points B & C you can see that the signal has come from a - voltage up to a + voltage, this represents an A/C signal. The line that runs through the middle of the signal is the 0v line, so anything under that line is a - voltage, anything above is a + voltage.


These patterns do relate to each other, but not directly. The inductive pattern triggers the ignition coil on and off as required, the A/C up and down signal is what triggers the coil. As explained in the previous post, the injectors and coil work in sink to allow combustion. If the distributor was malfunctioning and giving the wrong signal to the ecu, this could cause an incorrect output from the ignition coil resulting in engine mis-fire, stall etc.



Signal name; 02 vs injector
Volt/div/range; Channel A = 20v per div, Channel B = 1v per div
Time/div/range; 20mS per div

*Points A & C relate to each other. Point A is displaying the start of an injector pattern, if you observe when the pattern switches to turn on the injector you can see that the dwell time is quite long, meaning that the injector will be squirting a large amount of fuel, as the injector does this the 02 sensor is reading a rich mixture 
(If the 02 sensor is showing a high voltage this displays a rich mixture). When the injector pattern returns back to a normal idle pattern (point B) we can see that the 02 sensors signal at (point D) also switches to, this signal is low, this displays that the engine is running slightly leaner, which is acceptable when an engine is not under load.

As you can see, both of these signals relate to each other, as the fuel/air injects into the cylinder the 02 sensors are waiting in the exhaust to measure the amount of unburnt fuel and amount of oxygen, what ever readings these 02 sensor takes the ECU will conpensate for a lean mixture (to much oxygen particals, not enough fuel) by injecting a larger amount of fuel. If the sensors measure a rich mixture (to much fuel not enough oxygen particals) the ECU will compensate for this by cutting the amount of fuel injected into the engine.



WS1; Petrol Fuel Injector testing.

Vehicle make; ToyotaVehicle model; Engine (1ZZ)


1. Listen to the injectors as the engine is idling. Use stethoscope, vacuum line or long screwdriver. Be careful of moving parts. They should sound like a sharp tap, not a dull thud or nothing.
This is a crude test to see if they are being actuated, note results below;

All the injectors were functioning correctly, there was no abnormal sounds heard.

Can you access all the injectors?;

The injectors were very easy to access as we were using the 1ZZ engines in the down stairs room.

2.Check voltage to injectors when the engine is idling, or with the ignition on. This confirms that you have voltage to your injectors;

We backprobed the injectors to get an accurate reading, all the injectors were checked with the ignition on, they were 13.7v.

We then started the engine, the results are in the graph below;

We were quite surprised to see that each of the injectors measured at 13.9v, we were expecting that there would be a couple of variances just due to internal resistance, coil oscillolations etc.

3.With the engine running watch each injector firing by using an L.E.D test light, if the injector is functioning properly the light should flash to the speed in which you rev the engine to;
We started this by connecting our test probe. These are pretty simple to use, you hook one terminal of the probe up to a ground and the other up to the source you want to test.


The graph below shows which injectors showed a flashing light;

This list is just to show what each cylinder was Revving at idle.
Cyl #1; 793rpm
Cyl #2; 754rpm
Cyl #3; 801rpm
Cyl #4; 734rpm

RPM that each cylinder was @;


Cyl #1; 2500rpm
Cyl #2; 2500rpm
Cyl #3; 2500rpm
Cyl #4; 2500rpm

The results that I got for the test above were all jumpy so that Hz readings you see in the graph above are just an average of what was displayed the most when we were measuring. 

Also again the results were quite jumpy so I just took the average.

The pic above is of the calculations.


Give your conclusion on whether this is an acceptable way to test injectors and why?;

It is definitely an acceptable way to test injectors, it would be very useful if there was no oscilloscope around. Basically it is a good way of testing because you can get the readings with a multi-meter and make calculations with those, its very good if you cant afford an oscilloscope. There is a down fall to this way of testing though, taking all these readings aswell as making the calculations can be very time consuming.





WS2 flash codes;

   
Flash codes are a form of communication from sensors to ECU to the driver. They are used to determine any faults through-out the vehicle. 


The ECU will detect any faults there may be, each fault in the vehicle has a specific fault code which is given when the system is put in diagnostic mode. Most vehicles have different steps to them into diagnostic mode. 


The ECU will flash the check engine light a set amount of times to show what the flash code is, these flash codes can be noted and you can refer to the vehicles manual to look up what these codes mean.






The vehicle we used for flash codes was the toyota corolla 4afe engine. To start the procedure to extract the flash codes we first of all followed the steps in the user manual. We had to bridge terminals E1-TE1 using a jumper wire, this puts the vehicle in diagnostic mode. Sometimes people use a fuse in the jumper wire circuit to save shorts to the plugs.

We then turned the ignition on and noted any faults we came across. There was two codes that were given, the first one was;
24, we consulted the manual and that code represented (Intake air temp) circuit. Now we had to try and fix this fault correctly. First of all we located the IAT sensor, this took a little bit of looking around under the bonnet. We first looked at all the wires going into the connector, they were all fine. Then we noticed that the IATs plug was slightly unplugged, only enough so that there was no contact between the plug and the sensor. We plugged this back in, made sure that the connection was secure then we proceeded to repair the second code.

The second code was, 31 this code was (Vacuum sensor). We located the Vacuum/MAP sensor and proceeded to inspect it for visual fault. It was an obvious fault, the vacuum hose to the diaphram had been disconnected. With this unplugged the MAP sensor will not be able to operate. When then re-installed the vacuum hose, checked it for spliting and made sure there was no leaks in the hose.

Now that we had repaired all the faults found, we had to clear the codes to make sure that the problems had been correctly repaired. We did this by turning off the ignition, disconnecting the battery and leaving the engine alone for 5 mins. We turned the ignition back on and there was no more fault codes so we had repaired it properly.


The faults that had been put into the engine would effect it majorly. The vehicle would diffenately run very lean, it would also potentially be very sluggish because of the readings being given to the ECU, the ECU will not know what amount of fuel to inject etc.

Fault codes are a good way of fault diagnosis if you dont have access to a scan tool or if your vehicle is quite old and does not have an OBD system that is compatible with the scan tools. They are very useful if you have a brake down and there is no equipment handy to diagnose faults.

When the flash codes are found, we shouldnt just rely on them to diagnose problems though. Really we should do some voltage drop tests on the components that the codes are showing faults for. Also doing continuity tests to make sure that the earth on the connectors is sufficient.

Bad customer experience & treaty of waitangi blogs

Customer Story of a Bad Experience

Instructions:

discuss the following questions in your small groups. Then write your answers

in the space provided.

This is a true story.

The year was about 1958, in California, before there were strong consumer

laws. Don Higgins owned a laundry and dry cleaning business, in which he

used one of the new Volkswagen bus trade vans for his deliveries. He would

pick up dirty clothes from businesses (like restaurants and auto repair shops),

clean them and deliver them back. He liked his Volkswagen van: it had lots of

space to hang the clothes and it got good fuel economy. Up until recently, it

had been very reliable. But lately the engine wasn’t running very well. The

engine was regularly missing and had low power.

So in the morning, Don took his van to his local auto repair shop. He told them

it needed fixing, maybe just a tune up, and he got a ride back to his cleaning

business. Then in mid-afternoon, he went back to pick up his van.

To his surprise, the van wasn’t ready. If fact, the repair shop owner showed

Don the engine that was now out of the van. The exhaust valve for number 3

cylinder was burnt, causing the poor running engine and lack of power. The

shop owner said he could have the engine fixed and back in the van in 3 or 4

days. And the bill would be about $400.00. (In 1958, this was a lot of money.

Don’s monthly mortgage on his house was only about $120.00 per month.)

Don was very upset. He was so upset that I (Steve McAfee) heard about this

as the little boy who lived next door to Don.

Q.1; From Don’s point of view, what was wrong here? What did the shop do
wrong that upset Don so much. (After all, they were fixing his van.)

Answer; I believe that the workshop did not quote Don correctly, I think that any work that needs to be done should be made obvious, aswell as the price of the repair costs to the customer. All the conditions of the repair should explained accurately before the customer signs the contract between the work-shop and the customer.

Q.2; From the repair shop owner’s point of view, what was wrong with Don
getting upset at them? What did they do right or wrong?

Answer; I can see things from the work-shops point of view, I can see how the thought Don may-be in the wrong. Don did not specifically tell the work-shop what he would like to be done to the vehicle, he said "I need my van fixed" although he did say it "may" need just a tune up but that doesnt really allow the work-shop to draw any perimeters in reference to the repair, so to their understanding they were to repair the van at any cost.

Q.3; What should have been done in this circumstance? If you were Don, what
would you have wanted to be done?

Answer; If I were Don, I would have liked any repair costs to be quoted to me before any major repair is done, the complexity and amount of time needed to repair can be easily judged by the work-shop. I would also like the shop to draw up an agreement or produce a job-sheet which states all the work required, labour costs, part costs, any extra charges that will need to be made towards the repair.


Q.4; When the repair was finished, and Don went to pick up his van, he took the

van and did not pay the whole repair bill. Did the repair shop have the right to

hold the van until they got paid?

Answer; The work-shop would be able to detain the vehicle within their possession untill the bill was paid IF the repair costs and labour costs were clearly displayed then agreed to by the customer with a signature or evidence of approval. BUT because the work-shop did not give sufficient information towards the cost of the repair before the repairs were carried out and agreed to, Don has the right to remove his vehicle from their possession before he has paid the bill, because he has not been quoted correctly before the work has been carried out aswell as he did agree to work carried out before it was done.


Q.5;  If Don took the repair shop to court, what would you have ruled if you were

the judge? Should the repair shop pay for a replacement rental vehicle?

Should Don pay the whole repair bill? Should the repair shop pay Don for lost

business because he could not pick up and deliver clothes to his customers?

Answer; If I were the judge I would rule that Don should be re-emburst the money that Don used to get a rental car, because he needed a vehicle to try keep his buisness running for the days his car was off the road for. I would rule that Don and the work-shop come to an agreement of a lower price to be payed to the work-shop for the repair, I dont believe Don should have to pay the full amount of the money quoted by the work-shop. Finally I would rule that the work-shop reiemburse Don for some of the lost buisness he would have encountered due to the amount of time with-out his van, The reason for me not ruling that the work-shop reiemberse Don fully for buisness lost is because Don did have a car which I have ruled to be payed for by the work-shop, with this car Don still would have been able to do some buisness, meaning that he didnt lose out on all potential buisness.

Q.6; What New Zealand laws relate to this story? What do New Zealand laws
say should have been done in this case?

Answer; http://www.legislation.govt.nz/act/public/1993/0091/latest/DLM311053.html
Part 1, Guarantees as to tittle; This law basically states that anything that the Seller is trying to sell must be clearly displayed, if not various legal actions can be taken to ensure the consumer is given his rights in the matter.




Treaty of Waitangi

Treaty of Waitangi and Sustainability Worksheet

How does sustainability and freedom from pollution pertain to the treaty?

Instructions: Read the Treaty and answer the questions below. This may be used for theory classroom discussion.


What part of the treaty relates to pollution and sustainability? Write the phrase the relates to it here;

I have highlighted the phrase in the screenshot below;

What are the ways that modern civilization could polute the land, the sea or the air?;

I believe that polution could take place by Human waste which is not recycled properly, Modern day vehicles because they produce emissions from the gas being burnt, rubbish that is not bio-degradable (man made stuff that is un-able to be broken down by the earth) also industrial stuff like oil waste, all the chemicals they use to produce products etc.

What NZ legislation directs what should happen about pollution?;

The resource management act. This legislation basically believes in managing what happens to our country, pollution wise. So in a way they stop excessive amounts of pollution in our country

Blog 2 4848

WS4; Fuel pressure and Flow (Petrol only)

This blog was made to show people how to test and diagnose any fuel system faults they may be experiencing;


warning, be careful around raw fuel. It can catch fire! Use appropriate safety precautions. Keep sparks, flame, your body and your clothing away from raw fuel! Know where your fire extinguishers are and use them if necessary.

1. Locate the two closest fire extinguishers. 
There is one fire extinguisher in the room that we are working in (the workshop up by the paid for parking).


2. If you can, look up fuel Pressure specifications for the vehicle you are testing. 
The specifications read, 265 - 304kPa this is the fuel pressure specification for when the ignition is turned on but the engine is off. 265 - 304kPa, This specification is what the fuel pressure should be when the engine is on but the vacuum hose has been removed from the fuel pressure regulator. 206 - 255kPa, This specification is what the fuel pressure should be at normal, idling conditions (no vacuum leaks, regulator faults and sufficient fuel in the tank)


It is good to also relieve fuel pressure through-out the system if any fuel hoses or components are being worked on, this just allows you to do the job with-out making mess with fuel. Relieving the pressure is quite simple, start the engine, remove the fuel pump relay or fuse, keep the engine running untill the engine (turns off by itself/stalls) Double check that the fuel pressure has gone by cranking the engine to see if it starts, if it doesnt you have successfully relieved the fuel pressure, now remove a fuel line and have a rag handy to catch any left over fuel (their will still be fuel in the lines, just no fuel pressure this is because with-out the fuel pump running the fuel cant be pumped to create pressure) Remember to replace the fuel pump fuse/relay.
4. Attach a fuel pressure gauge (if you haven't already got one) and notice which scale on the gauge you will be using.  Briefly crank the engine over, just enough to gain fuel pressure, check for any leaks and take note; (for this experiment we did no have to do this as the engine had a pressure gauge installed already, and our gauges displayed kpa & psi which is good because the specs were in kpa)


No leaks were found, we checked all the connections and stuff to make sure their was none, just because we didn't have to install the gauge so we doubled checked to make sure.


5. Measure the fuel pressure with the key on, engine off;
Our pressure under these circumstances displayed 270 kPa
6. Measure the fuel pressure with the engine idling, watch the pressure for a few mins; 


As the engine was started our fuel pressure was 270 kPa, but as time went on the pressure dropped to 250 kPa.


7. Measure the maximum fuel pressure by using the fuel line clamp tool provided by your tutor. (do not do this for an extended amount of time);

When we used the tool to clamp the fuel line, we noticed a high jump in fuel pressure, our maximum fuel pressure jumped up to 600 kPa, this is the reason why it says not to hold it at this fuel pressure for a long period of time because it can damage components and maybe even burst fuel components.

8. WOT; with the engine idling disconnect and plug the vacuum line goning to the fuel pressure regulator.
The pressure recorded was 300 kPa, this test shows what the fuel pressure would be at full throttle, because when the engine is at high capacity the vacuum will not be as high allowing the regulator to regulate the fuel to a higher pressure due to the vacuum not being strong enough to open the diaphram inside the regulator, with the vacuum line off the regulator is reading atmospheric pressure, which basically means that it is going to operate to its full capacity meaning that the diaphram within the regulator wont open much.


9. Residual Turn the engine off and watch the fuel pressure for five minutes;
As time went on the fuel pressure increased from 250 kPa (idle pressure) to 270 kPa (residual pressure)

10. Fuel flow Hook up equipment to read fuel volume;


This test was not applicable to us as we did not have the gear to perform this test.


11. Replace any vacuum lines removed, remove the fuel pressure gauge, turn ignition on & off, check for leaks, Any leaks found?
There was no leaks found after performing these procedures.

Make sure the engine is running fine before leaving it.
12. Explain why it is important to know a vehicles fuel pressure/flow;
It is important to know this information as it can very useful knowledge to have if you encounter any fuel system faults, because it gives you a basic understanding of how the fuel system works. With a basic understanding of how this system works you can start to diagnose and rule out any faults that could be causing a vehicle to run incorrectly. For example, say we had a little bit of a misfire at idle, we could easily connect a pressure gauge, look up the manufactors specs and compare them to the readings that the gauge is reading. This then shows you if theres any variances, which can help you to rule out mis-functioning parts.

13. Describe the symptoms a vehicle would give with each of these cases;
Low fuel pressure;


With low fuel pressure the car may idle fine, but as throttle is applied the vehicle may hesitate to accelerate and also not produce the power needed for the situation the vehicle is in. The engine will run very rough under acceleration untill correct fuel pressure is achieved.


Low fuel flow;


If the fuel system has low fuel flow, the fuel rail will not be supplied the right amount of fuel, this means that the injectors will have a insufficient fuel amount to allow for a full injection spray aswell as the fuel pressure at the injectors wont be sufficient. Basically the engine will misfire and not produce power as load is applied to the engine.


High fuel pressure;
High fuel pressure will cause the air/fuel ratio to be quite rich at idle, meaning the economy and emission levels will be bad. As the engine load increases, the fuel pressure will be used correctly because at high engine load the fuel pressure is high anyway so for the amount of work the engine is doing, the engine economy and emissions will be correct.

Faulty fuel pressure regulator;

Depending on the fault, the fuel pressure regulator could give two different conditions; One fault being that the diaphragm inside the fuel regulator could be sticking open, this would cause low fuel pressure (explained above) Another fault the regulator could encounter would be that the diaphragm is stuck close or the vacuum line to the regulator is leaking, this could cause over pressurizing of the fuel (also explained above).


This concludes my post, all the tests conducted came out fine, they were within the manufactors specifications.


Image reference;http://www.google.co.nz/imgres?q=fuel+pressure+gauge&um=1&hl=en&rlz=1C1CHKB_en-GBNZ450NZ450&biw=1366&bih=667&tbm=isch&tbnid=HBg7ZHa-ExhD2M:&imgrefurl=http://www.justanswer.com/car/12ajq-1997-jeep-cherokee-4-0l-seem-problems.html&docid=gD52wsNriHO85M&imgurl=https://w05.dealerconnect.chrysler.com/service/mds2002/serviceInfo/en_US/80468d30.gif&w=640&h=639&ei=J-fVTsWfC6zMiQLZydXCDA&zoom=1&iact=hc&vpx=812&vpy=424&dur=6708&hovh=161&hovw=161&tx=108&ty=140&sig=109698256239734078907&page=2&tbnh=134&tbnw=134&start=18&ndsp=20&ved=1t:429,r:4,s:18





Practice Back-Probing connectors on the bench;

This isnt a very hard experiment but I believe that knowing how to back-probe is one of the most important things in the subject, if you dont know how to back probe correctly the components you are testing may-be damaged (meaning you will owe people $$$)
First of all we will start with a simple lesson on how to use a multi-meter;

1.0; Meter reading Ohms with wires not connected;
1.1; Turn on the multi-meter, set it to measure resistance (ohms), make sure the leads are not touching anything. What is your reading? and descibe what this readout means;

Our reading shows O.L. This is because this is basically an open circuit. Resistance will be infinite if there is no link between the two terminals.

2.0; Meter reading Resistance with wires connected;
2.1; Turn the meter on, set the test to Ohms(resistance) and touch the leads together;
Our reading shows 000.5 Ohms.

2.2; Describe what the read out above means when doing electrical testing;

This reading basically just displays small resistances with-in the multimeter circuitry, for example the test leads will almost always have a tiny amount of resistance in them.

3.0; Practice back probing connectors
3.1; Find a hard shell connector, with the attached terminals and wires that you can test
3.2; Back probe a wire on one side, probe gently from the fron on the other side, and measure the resistance, Record the reading;
The reading shows 0.51 Ohms

3.3; How can you tell if you've made a connection between the wires?
I can tell because the reading shows a slight resistance, this basically indicates that a connection has been made between the wire and also that there is a slight internal resistance with-in the wire.


Image reference;http://www.google.co.nz/imgres?q=probing+a+electrical+connector&um=1&hl=en&sa=N&rlz=1C1CHKB_en-GBNZ450NZ450&biw=1366&bih=667&tbm=isch&tbnid=oaQqoS9JuyIebM:&imgrefurl=http://www.agcoauto.com/content/Glossary&docid=ZxdhQUBNFkBRWM&imgurl=http://www.agcoauto.com/content/images/electrical/back_probing_circuit.jpg&w=278&h=216&ei=k-bVTq_1CcWdiAK_ooGHDA&zoom=1&iact=hc&vpx=975&vpy=70&dur=1445&hovh=172&hovw=222&tx=72&ty=125&sig=109698256239734078907&page=1&tbnh=154&tbnw=196&start=0&ndsp=19&ved=1t:429,r:5,s:0




WS5; Scan Tool Diagnostics

Vehicle being used; Mazda Familia 323, 1998.

This test exercise is a basic scan-tool exercise used to teach basic scan-tool skills to students.

1; Scan Tool Data;
1.1; Obtain a vehicle that is suitable for this test.

We have chosen to us the mazda familia in the workshop as it has ob2 two (on board diagnostics two) because it was produced after 1996. This is a system in which the ECU provides fault information to the scan-tools we are using. Cars produced before 1996 generally used obd1. The difference between these two diagnostic features is that obd1 focuses more on just giving engine fault codes which can be used to find what the fault is by looking at the fault code menu in the vehicles user manual. obd2 has alot more detail as to what the faults can be, this is useful if you dont have access to a particular vehicles manual. There is also another difference between the two diagnostic devices; The port in which the scan-tool connects through with the ECU can be located anywhere on different obd1 vehicles. A regulation was brought in when obd2 was being produced, Every obd plug must be with in 1 meter of the vehicles steering wheel. This makes it alot easier to find the obd plug.




1.2; Connect the scanner, power it on, follow the instructions and input the correct vehicle information it asks for so you can view the data.

Most scan tools will ask you the; Make of the vehicle, The model, The engine capacity, Chasis code, Jap import/Euro import/NZ new and Year of the vehicle. Some may ask for different details but in my experience these are the only details they generally ask for.
This is just so that the scan tool can calibrate properly to your specific make/model because some vehicle models have slight variances which can cause differences in the data you recieve from the scan tool.




1.3; Find the data for the information listed. Turn on the engine and record the live data in the graph below;

This graph shows the live data that the scan tool had at the time I recorded it. As you can see some of the boxes were left blank, that is because the mazda's obd system did not have communication with some of the components in the graph.

2; Trouble Codes or fault codes

2.1; Find where the codes are listed;

 

The codes were actually listed with-in the scan tool itself, all the details that we needed were listed quite clearly displayed in the trouble code list.

2.2; Record any codes, and what system and condition they descibe in the chart below;

We figured out that these fault codes were faults that had been corrected from the last students, but they had not remembered to clear the codes, so these readings were actually old readings from tests before our tests.

3. Lecture put in fault;

3.1. Find your lecturer and have him create a fault under the hood (no peaking)

 

We had one of our tutors put a fault in the engine somewhere so that we could have a go at scan-tool diagnosis.

4. Record new codes;

4.1. Look up codes in the scan tool, and record them to the chart below;

5. Find what data has changed;

5.1. Have a look through the scan tool data to see what PIDs (Parameter indentification of system voltages) have changed. Do any readings not make sense? Also record the data changes in the chart below;

The reading variances that stood out the most to me was the ECT reading and INJ pulse rate, as they had changed so much that there was no signal from them to be displayed. Also the code given by the scan tool was an ECT trouble code, so this gave us a slight hint as to what the issue was.

6. Visual inspection to find fault;

6.1. Do a visual inspection under the hood to try and locate where you think the problem is. Use the information displayed from the scan tool to give you a guideline as to where to look.

We had a quick look under the hood of the vehicle and we found that the main ECT plug was unplugged, that's why we weren't receiving any signal from that sensor, also the vehicle wasnt starting thats why our injection pulse rate was reading 0, Some vehicles wont start with the ECT plug unplugged, our mazda is one of them. So if the vehicles not started obviously there cant be an injector pulse rate, well a constant injector pulse rate that is.

7. Repair fault;

7.1. Plug connector back in, or repair the problem as required, describe what you did;

First of all we started by inspecting the wires going into the ECT connector to see if they were visually fine, free of corrosion, still insulated etc, then we reinstalled the connector back onto the ECT sensor, then we double checked that all the wires in the connector were sitting inside the connector properly so that there is a good connection between the connector and sensor.


8. Recheck Data PIDs;

8.1; Recheck data with scan tool, then record the changes in data in the chart below;

First of all we started the engine to make sure that we had correctly installed the ECT connector, the car started fine so we recorded the data and put it into the chart below;

As you can see by the data recordings in the chart, all the signals are back to normal, this proves that we diagnosed the fault correctly and repaired it accordingly.

9. Clear codes, Describe what you did to clear the codes;


The scan tool we are using has a function in it that can contact the ECU and ask it to clear the codes, we used this function to erase the fault codes that came up after we had fixed the problem.

10. Recheck for codes and record them below;
We did another fault code check after we had erased the codes in the last step, the check came back clean, we didnt have any more fault codes given to us by the ECU, so all the faults had been successfully repaired.

11. Discuss the importance of live data when fault finding;


Live data provides us with live information as to what signals the sensors are reading at different vehicle speed, load, conditions etc. This can make it alot easier to diagnose faults because by observing the live data and comparing with appropriate manufactor specifications we can understand what the parameters of each signal should be under different conditions. This gives us alot more direction as to what potential faults may-be.

12. Explain the need for parameters when checking live data;

Parameters give us a range of what acceptable signal variances should be for specified components. Basically parameters allow us to decide weather components being tested meet the specifications that require the components to function correctly. For example, Say if we were to test the resistance of a high impedance injector just by disconnecting the injectors plug and probing the injector terminal and ground, Lets just say the specification is 10-13.5 ohm, but our test comes back showing around 20 ohm, this obviously does not meet the specification set by the manufactor, this is why parameters are needed, with-out them it would be so much harder to diagnose faults.


13. Discuss how a scan tool can aid you with fault finding;

A scan tool is a very usefull device for fault finding. Scan tools can find faults that may be hard to diagnose with a multi-meter or oscilloscope. This is because the scan tool can read problems straight from the ECU, modern day cars have self diagnosis features, if anything through-out the car is wrong the ECU will show a trouble code. A scan tool is a much easier way of reading fault codes as it doesnt involve having to read flash codes.

Blog 1 4848(off car)

Air flow/mass sensors (MAF)  

We did not conduct the experiments for the hot wire airflow meter in class due to insufficient gear, but I think these meters are a very important thing to show understanding about because most modern cars use these meters rather than the Vane and Vortex type meters due to the reduced size, weight and amount of parts used in the production of the hot wire meter.

This sensor works by measuring the amount of incoming air. The sensor has a Hot wire in which a constant current is applied to, this wire is a temperature coefficient resistor, usually of positive temperature coefficient nature. This hot wire is placed in the air stream of the incoming air, basically as air flows past this hot wire, the resistance of the hot wire is changed in accordance to the amount of air flowing in, as the amount of air flowing in rises, the resistance drops due to the heat of the hot wire dropping and because its a temperature coefficient resistor (ptc) the resistance will drop as the air flow increases.


The resistance change corresponds to output circuit, this circuit gives a reading to the ECU (electronic control unit). For example, at idle our airflow wont be very high, so the output voltage and frequency wont be very high. When the engine is at WOT (wide open throttle) our airflow will increase significantly which will give a high output signal and a high frequency. These output voltages and frequency's correspond with other components like the o2 sensor, to allow accurate amounts of fuel injection and ignition time. Sometimes manufacturers will include an internal cold wire in the airflow meter which basically measures the density of the air flowing through the airflow meter and allows the ECU to make any changes to injection rates and timing according to the density of the air.


 There is also another feature that some manufacturers have included in these sensors, as the vehicles ignition is turned off there is a large voltage spike induced to the hotwire of the sensor to allow it to burn of any carbon dust build up, if there is carbon dust on the hotwire the sensor output readings could be incorrect meaning the ECU could be giving the engine the wrong amount of fuel and ignition timing.






Here is a video to display the basic function of the MAF sensor, along with a small amount of fault finding procedures;

Test procedures;

Step 1;
We can test the MAF sensor by hooking it up to a 12v power supply, 5v reference voltage and a ground. From here we need to hook a multimeter up to the signal out pin and a good earth. Set your multimeter to voltage test. Now we need to blow air through the passage way, you can do this by simply using your mouth to blow air through but a more effective way is to use a hair drier set on a cold setting. As the amount of air flows past the heated element we should notice a drop resistance causing the output voltage to be higher. If you dont experience this whilst testing you MAF it may be faulty.



REFERENCE;

All the information included in this post was taught at unitec, aswell as http://www.autoshop101.com/forms/h34.pdf and http://www.sensorland.com/HowPage060.html

Picture: http://www.google.com/imgres?q=maf+sensor&um=1&hl=en&sa=N&biw=1680&bih=956&tbm=isch&tbnid=hf6JyTRp8wTKWM:&imgrefurl=http://www.aa1car.com/library/maf_sensors.htm&docid=S1IX39h6_NB5JM&imgurl=http://www.aa1car.com/library/maf_sensor_ford.gif&w=557&h=395&ei=leuhTo_DA8WtiQeg793DBg&zoom=1&iact=rc&dur=195&sig=102311554416164353344&page=1&tbnh=130&tbnw=183&start=0&ndsp=41&ved=1t:429,r:0,s:0&tx=96&ty=72

Video: http://www.youtube.com/watch?v=sSuL58YEH-E




MAP sensors (maximum abosulute pressure sensor)

The MAP sensor was designed to measure incoming air pressure (absolute air pressure). This measurement that the MAP sensor makes is then sent to the ECU, this information is very important because the readings given by the MAP sensor allows the ECU to make calculations towards the air/fuel ratios


The diagram above shows the pressure sensor input, the 5v input, ground and the signal out wire. The sensor has a 5v input signal which is a constant 5v. As the pressure sensed by the MAP changes, the resistance inside the sensor is changed, so when the resistance is changed obviously the output signal has to change to. This is where the signal out wire comes in, when the resistance internally changes the output signal changes to, for example when the pressure input rises, the resistance corresponds to this by rising aswell so with a higher resistance the voltage output signal will be lower.


The MAP sensor is commonly found in most modern vehicles now days, mainly EFI (fuel injected vehicles). Most vehicles use etheir a MAP sensor or a MAF sensor to determine pressure or airflow if a MAF sensor is being used.

The diagram above shows the circuit that this particular sensor uses, as you can see terminal 61 is the 5v supply terminal, 36 is the output signal to the ECU and 43 is the ground to the sensor. The squiqily line inbetween 5v supply and sensor ground is the variable resistor, the position of the sensor output line is determined by the position of the plunger which is moved by the amount of pressure coming into the sensor.
Test procedures

MAP sensors are fairly easy to test for correct function,

Step 1; Hook up 5v power supply to the power input terminal, make a sufficient ground to the ground terminal.

Step 2; Set your multi meter to DC voltage test, attatch the positive lead to the output line and the negative lead to the ground line on your MAP sensor (the terminals can be determined by etheir reading the corresponding manual or doing a little bit of research on the internet).

Step 3; Aquire a pressure pump to pump pressure into the pressure input of the sensor, as the pressure is raised, the voltage reading should drop, if this happens with the voltage decreasing/increasing smoothly this  then your sensor is working with-in specification. If the voltage out-put is quite jumpy then you may have short circuits through-out the resistor meaning that you will have to replace the sensor.

Throttle position sensor

The throttle position sensor measures the angle of the throttle position, this sensor is one of the most important sensors for correct drive-ability because it corresponds with other sensors to allow the ECU to make accurate decisions towards fuel injection, timing and spark ignition. 

This sensor uses a reference voltage which is usually around 5v, a signal out voltage and a ground. As voltage is applied to the reference circuit it goes through into the sensor where there is a variable resistor, ground and output signal. The output signal is the signal that is sent to the ECU, this signals value is completely determined by the position of the signal output wire on the variable resistor. The position of the output signal wire depends on the drivers intent, as the driver steps on the accelerator pedal, the rotor(spindle) inside the sensor moves (the variable resistor) so as this rotor is moved, the resistance also changes which means the signal output changes accordingly. 

At idle the TPS will give a low signal to the ECU, this just lets that ECU know that there is no load on the engine and it needs to keep the engine at a constant low idle speed. As you can see by the chart, as the throttle shaft changes angle so does the resistance, it drops. So basically that means the voltage output rises. When the output rises the ECU knows that the engine is under load, from here the ECU can make calculations as to how much air/fuel needs to be injected etc.

Test procedures;

Step 1; Test the supply voltage to the sensor by locating the sensor, unplugging the sensor plug and attatching the red lead of your multimeter to the reference pin and attatching your ground wire of the multimeter to the ground pin of the plug. Make sure your ignition is on but the cars not started up. After following these steps your multi-meter should read 5.0v without any hesitation and jumpyness with the signal. If it does not show 5.0v constantly you may have a problem with reference voltage supply.

Step 2;
Now we are going to check the signal voltage to the ECU from the TPS. First of all, start by plugging the TPS plug back into the TPS. Now we are going to back probe the signal terminal using a pin or safety clip, what ever we have handy, we also need to back probe the sensor ground aswell, but be careful not to let the two probes touch as it will cause a short which could damage the sensor. Now we connect the red lead on our multimeter to the signal back probe, and we connect our black terminal to our ground back probe. We have to start the engine for this one, once the engine is started move the tps manually, smoothly move the tps angle and carefully monitor the voltage on the meter, the voltage should start off at 1.0v without any angle on the tps, when angle starts to be applied the voltage should move up smoothly towards 5.0v without any hesitations and jumpy signals. If you notice any jumpy signals and hesistations in the signal output you may have a faulty MAP sensor, this means you may have to replace the sensor.

Step 3;
This test is similar to test 2, backprobe and connect terminals as said in test 2, but you will not need to have the ignition on or engine on because this is a resistance test. Basically adjust the angle of the tps manually as we did for test 2 and note the OHM reading on the sensor watch the resistance go up and down as the angle is adjusted. If there is no huge jumps in the resistance when the angle is changed the sensor itself may be fine. If there is you may have to replace the sensor as they are not repairable.







 

Knock sensors

Knock sensors were designed to detect pinging (detonation) going on inside engines, detonation can cause serious damage to an engine if it is carried on for long periods of time. Detonation is when a secondary flame front inside an engine cylinder ignites the fuel before the spark ignition system does, which of course stuffs up timing and injection rates etc.

The knock sensor is a pretty basic set-up, it has a signal out wire, it does not need an earth because it earth's it-self through the block in which it is placed in, although some do have an extra wire for earth depending on the area the knock sensor is situated it. The knock sensor uses the piezoelectric effect, this law states that when a crystal is vibrated or pinged it produces its own voltage. That voltage is sent through the signal line to the ECU to let it know that it needs to make changes to the timing to allow the detonation to stop.

Here is a quick video that physically shows how the sensor works;

Test procedures;

Step 1;
The best way to test these sensors is to use an oscilliscope, Basically because they are alot more acurate because the capture a pattern where as a multimeter just captures the voltage. By seeing a pattern it is easier to determine faults. Hook your oscilliscope up the signal out line of the sensor and find a decent ground on the sensor. Now we need to tap the bottom with something that will allow for a decent shockwave, something like a coin of metal rod, anything the has abit of weight behind it. As you tap the sensor, you should see the pattern of the oscilliscope jump up really quickly. This shows the sensor is working properly. If you are having trouble getting a signal, it could be how your osilliscope settings are set but usually it shows that your knock sensor is not functioning properly. This means you'll need to replace it.
Step 2;
Really the easiest way to test one of these sensors is to use a scan-tool to read any fault codes, if your knock sensor is faulty the scan-tool will bring up a code number, this number can be looked up in the user manual of the vehicle, the code will explain what is wrong with the sensor.

Thermo Fan Switch

Thermo fan switches are designed to switch the fans on when the temperature of the engine coolant reaches a certain level. The sensor has a constant signal to it, but its not always grounded.

The blue strip you can see in the diagram above is a Bi-metallic strip. This Strip can allow the circuit to complete and let the fans have power so that they can cool the engine. The bi-metallic is made up of two different metals, one of the metals expand at a higher rate than the other so as one metal expands it forces the other metal to bend, and if you look at the diagram if the bi-metallic strip bends enough it will allow there to be a connection through the sensor to earth the fans. So basically when the engine coolant reaches a high enough temperature it will cause the strip to bend and allow the circuit to complete.

Usually this circuit doesn't provide earth to the fan directly, it usually earth's a relay to allow the relay to provide power to the fans, because the fans are already hooked up to an earth source.

Test procedures;

Step 1;

If the fan switch is off the car the procedure is quite simple, find a pot fill it with warm-hot water around 60 degrees c (no higher as this experiment wont work properly). Monitor the water temperature with a thermometer, now we are going to hook a multimeter (using resistance measurement) up to the input and output terminals of the switch, after this is done we need to submerge the switch into the water (at this point the multimeter should be reading O.L). Now we need to heat the water with an element, we have to carefully watch the temperature and the multi-meter because a correctly functioning switch should switch at around 80 degrees c (some thermo fan switches will switch higher or lower depends on the manufactors spec). As the heat comes up 80 degrees or so we should see that the multi-meter changes from O.L to a small resistance. This tells us the switch is functioning correctly, if you dont see this reading at around 80 degrees you may have a faulty switch.

02 sensors

The aim of every vehicle manufactor is to achieve the perfect air-fuel ratio. An air/fuel ratio which gives the lowest amount of emissions/economy along with the best amount of performance.

The air/fuel ratio is achieved obviously by air and fuel, but how is the mixture determined to achieve perfect air/fuel ratio?

The 02 sensor is the answer. There is one 02 sensor which is usually placed just after the exhaust manifold, this senses what the air/fuel reading is, then the sensor works in-sync with the catalytic converter. The converter strips any unwanted emission gases that are flowing through the exhaust so that the atmospheric air is not polluted. Once the gases have flown through the cat, there is another 02 sensor, this sensor now reads what the air/fuel ratio is after the catalytic converter. The second 02 sensors signal is the one which matters the most because if the mixture is not right after the catalytic converter we can polute air or potentially damage our vehicles. The second 02 sensor reads what the air/fuel ratio is and sends this signal back to the ECU, the ecu then reads the voltage sent to it and makes changes to the ignition timing injection timing/rate etc. 

So this basically means that the 02 sensors jobs are to help the ECU to achieve the perfect air/fuel ratio for the conditions.

The sensor is very useful for all conditions the vehicle may come under. For example, a vehicle is travelling along a straight road and its running perfectly, the air/fuel ratio is reading a steady 14.7:1 (lambda 1) the driver approaches a very very steep mountain, this mountains height is huge. As the vehicle goes up in the mountain the altitude to ground level goes up, as altitude is increased the density of the air decreases, so therefore the engine wont run exactly as it did on the straight road. The 02 sensors will then sense the air fuel ratio, they'll see that the engine is running slightly rich as the intake of air to the combustion chamber will be less dense meaning less oxygen molecules thus the engine is running rich. The 02 sensor will let the ECU know that the engine is running rich, the ECU will make changes to the injection rate/ignition timing accordingly. 

There is a couple of main types of 02 sensors, There is the standard narrow band sensor this operates on a 0-1 volt scale, 0 being lean .5 being stoich and 1 being rich. These sensors are usually used on cars which are standard from the manufactor, meaning there is no aftermarket modification. The voltage is then sent to the ECU which lets it know if the engines rich lean or stoich (stoich means good air/fuel ratio).

There is the wide band, this operates on a 1-5 volt scale, Obviously this is a much larger scale, this is good if you have modified the vehicle, because it gives a more acurate reading to the ECU, instead of telling the ECU if its rich lean or stoich, the wideband can let the ECU know the exact amount of air or gas its reading which is good for high performance tuning, the more acurate your measurements are the better performance output you'll get.