WS3A

Throttle Position Sensor

A - Throttle opening and more air is coming in as the throttle is opening.

B - The throttle is stable for a small time and then starts decelerating. Throttle closing slowly.

C - Throttle is closed

D - Engine is accelerating heavily and fully opening.

E - engine at wide open throttle and stays wide open for a while

F - decelerating again and going back to closed throttle.

Drawing A - in red shows that the signal is not grounding back to the ecu.There is an open circuit in the earth wire that goes back to the ecu. Therefore the signal is always reading supply voltage as the voltage is not dropping in the variable resistor.This can be also caused if the signal has shorted to supply voltage. By this voltage the ecu will always think the throttle is fully open. The engine probably wont start as it will flood the engine thinking its at wide open throttle

Drawing B - Theres no reference voltage to thew TPS. Theres no signal voltage out when theres no reference voltage.

Drawing C - If there is a high resistance at ground. The signal is always high even at closed throttle. As there is high resistance at the ground, there is a less voltage drop at the variable resistor therefore the signal picks up a higher voltage even at closed throttle. The engine will be very rough and run rich as it will think that its at full throttle when its only opening a little bit. The fuel economy will go high and run really badly.

Map Sensor

A - The engine decelerating and the throttle is closing causing more vacuum in the engine so the voltage goes down.

B - At closed throttle the vacuum is high so the voltage stays low.

C - Thew engine accelerated so there was more air pressure and vacuum goes down so voltage increases.

D - engine decelerating and throttle closing co less air is  coming in and vacuum is increasing so the voltages decreases.

A high resistance at ground will mess up signals. The signal outputs will go down as there is mores resistance added in the circuit with the wheat stone bridge.More resistance added to the circuit will make the output low. So the voltage output is lower as shown in the graph in red. With this problem the engine will operate really badly.  There will be more air coming into the engine but the map will tell the ecu that there less air coming. The engine will be running very lean. Will be hard to start and engine will keep dying at idle. It will have no power. 

Engine Coolant Temperature Sensor

A - Engine is cold so the voltage output is high.

B - as the engine is warming up  the voltage is dropping

C - engine is warmed up or hot so the voltage is really low.

If there is a open circuit in ground, signal will always read 5v as thats is the supply form the ecu and there is no voltage at the thermistor and the internal resistor in the ecu.

the fault in my graph has a high resistance on the ground. Voltage drop will always be less at the internal resistor as there is more voltage needed as there are more resistance along the circuit. The thermistor will have a voltage drop and the resistance. The signal is always hight telling the ecu that the engine is still cold. The ecu will then increase the injection timing. The car will run rough and fuel economy will be high. It will be also have bad emissions.

Intake Air Temperature Sensor

This works the same way as the ECT.

A - The air is cold so the voltage is high

B - the coming in a little bit warm so the voltage drops.

c - the air is hot so the voltage is really low.

Fault b is showing an open circuit in the ground. The signal stays the supply voltage from the ecu which is 5v. This tells the ecu that the air is cold which mean the air is more dense so the injection time should be increased.

Fault A shows a high resistance at ground. Therefore there is less voltage drop at the internal resistor because more voltage will be used up at the resistance on ground and thermistor. Therefore the signal sees high voltage all the time. The ecu will think theres always colder air coming in the engine therefore it will richen the fuel mixture. The engine will be running rich all the time which will create high fuel usage and bad emissions. The engine will not work efficiently.

MAF Sensor

A - The engine is accelerating slowly

B - this is the engine at idle.

C - Engine accelerates heavily so the voltage increases quickly.

D - Engine is decelerating

The red pattern on the graph is caused by dirty or contaminated hot wire. The reading will always be incorrect. MAFs with contamination should be replaced.

The contamination creates a hesitance in MAF circuit. The resistance increases in the platinum hot wire therefore the output will always be low. Low signal  indicates the ecu that theres is less air coming in even though its at wide open throttle. This will cause the engine to always run lean. The engine will loose a lot of power and might shut off at idle. The combustion temperature will be very high causing wear. the engine will inefficiently.

Oscilloscope Patterns (WS3)

Ignition Primary

Battery voltage come into the coil. At (A) the coil gets grounded and the magnetic field is created across primary windings.

B - As the coil was ungrounded the magnetic field collapsed across the primary windings making a voltage spike of 300v.

C - This is the burn time or spark duration

D - coil oscillation. this is the oscillation between the primary and secondary winding.

Petrol Injector

A - this is the supply to the injector which is the battery voltage.

B - This is when the injector is grounded and this is the time the injector open to spray fuel

C - This is the injection time. This is the time the injector stays open and injects in the fuel.

D - The injector is ungrounded which closes the injector. This causes the magnetic field to collapse in the injector windings and voltage spikes up to 45V.

E - The voltage goes back to battery voltage.

Oxygen Sensor

This  is a zirconium type oxygen sensor  and it is in closed loop and is cycling. At (A) the voltage is high to 0.9v this indicates a rich mixture where there is less air in the exhaust. The signal goes to the ecu telling the fuel mixture is rich.

B - the voltage goes down to 0.2v. This tells us that the air fuel mixture is lean. The oxygen sensor detects high amount of air in the exhaust. This voltage goes to the ecu indicating a lean mixture.

RPM (crank)

A - reluctor tip is getting closer to the coil therefore air gap gets smaller and the magnetic field is increasing.

B - Air gap is smallest here and full magnetic saturation of the pickup has reached. The reluctor is lined up with the coil.

c - As the reluctor moves away magnetic field collapses across the coil and induces a voltage in the opposite direction. Back EMF.

D - reluctor tip moving away from the coil so voltages goes back to 0v.

E - Peak to Peak voltage (2.2v)

Hall Distributor

A - This is the dwell time. This is the chopper plate is is cutting the magnetic field. The voltage gets high.

B - when the chopper plate moves away from the magnets, the circuit gets grounded so the voltage goes to 0. This is the firing time of the coil.

Cam Position Sensor

A - The reluctor wheel is getting closer to the stater the magnetic field increases therefore voltage is increasing.

B - As the reluctor wheels moves past the stator, the magnetic field collapses and voltage is induced in the opposite direction.

C - showing the wheel moving away form the stator and voltage is getting back to 0.

Dual Patterns (WS3B)

MAP against Injectors

When there is less vacuum the map signal voltage gets high telling the ecu that there is more air pressure in the engine, the ecu then grounds the injector longer so that it sprays more fuel to compensate with more air coming in the engine.When map signal voltage gets low the injectors is grounded for a short time. So When the output signal voltage for map increases the injector gets grounded longer.

Oxygen Sensor against Injectors

As we increased the rev on the engine the injector was feting grounded for longer and output signal of the oxygen sensor went high telling telling the ecu that the fuel mixture is rich.When the oxygen sensor detects less oxygen in the exhaust it sends out out a high signal of 0.9v telling the ecu that the engine is running rich. Then the ecu will decrease the time the injectors are grounded to make the fuel mixture leaner. When the oxygen sensor sends out a low voltage of 0.2V it will tell the ecu that the engine is running lean so the ecu will ground the injectors longer so it sprays more fuel to get the mixture rich. The oxygen sensor cycles from rich to lean to control emissions and to keep the fuel mixture stoichiometric , doing this the injector is open longer to make the fuel mixture rich and open less to make the fuel mixture lean.

RPM distributor against Injectors

As the engine rpm increases the RPM signal frequency increases therefore dwell time and firing time of the coil is faster. So the spark is comes on faster. When engine RPM increases it needs more fuel so the injector gets grounded longer giving out more fuel as the engine is sucking in more air. When the engine is decelerating the RPM signal decreases therefore the injection time gets less. The RPM signal gives signals to the ecu and the ecu then control the injection time.

Injector Voltage and Injector current

1 - current is not flowing.

2 - current increases in the winding of the injector and the longer the injectors are open the higher the current gets higher.

3 - injector closed and open circuit so the current goes down to 0.injector ungrounded so current is not flowing.

A - battery voltage at injector

B - Injector is grounded.

C - injector is grounded therefore is open and spraying fuel.

D - Injector closes therefore a voltage spike of 50V.

E - voltage gets back down to battery voltage.

When the injectors open current starts flowing and slowly increases when is kept open and then goes down when it closes.

Ignition Primary Voltage against Ignition primary current

When the coil gets grounded the current builds up slowly and then hold the current to 6amps. As soon as the coil is ungrounded the the magnetic field collapses therefore the current goes down 0 and voltage spikes up to 300 v in the coil. So when the coil is grounded a magnetic field is created in the windings so the current  build up and stays in the windings until it the coil is ungrounded for the firing voltage. Thats why the coil gets hot when power is supplied though it for long.

Primary and Secondary Ignition Patterns (WS8)

Primary and Secondary Ignition Patterns

I did testings on a Toyota 4A-FE engine. I set up a ignition oscilloscope with the engine warmed up and running and i recorded  firing voltage, burn time, burn voltage and dewll time.

Ignition Primary	CYL 1	CYL 2	CYL 3	CYL 4
Firing Voltage	300v	300v	300v	300v
Burn Voltage	40v	40v	40v	40v
Burn Time	1.4ms	1.4ms	1.4ms	1.4ms
Dwell Time	4.6ms	4.6ms	4.6ms	4.6ms

All readings look normal. The readings are constant for all cylinders. The engine is running smooth  without misfire and hesitation. Constant operation tells the engine is runnig efficiently.

A - Coil gets grounded which is the dwell period.

B - Coil is ungrounded, primary winding is open and the magnetic field collapses and voltage spikes up to 300V. This voltage is applied to the secondary windings.

C - this is the burn time, the duration of the spark.

D - Coil oscillation. The coil should display minimum of peaks(both upper and lower). If a loss of peaks in oscillation shows, coil should be substituted.

This is a stacked display showing each primary pattern for each cylinder. This is useful to diagnose faults with the engine by comparing each pattern for each cylinder.

When we increase the RPM on the engine the dwell time increases as it takes longer to saturate the coil and the burn time is longer to as the air fuel mixture is more and richer.

Secondary Voltage Patterns

I got the engine warmed up  and idling. I connected the ignition oscilloscope to view secondary ignition patterns. When i snapped the acceleration i recorded firing voltage and burn time.

Ignitiion Secondary	CYL 1	CYL 2	CYL 3	CYL 4
Firing Voltage (KV)	13KV	13KV	13KV	13KV
Burn Time (ms)	1.6ms	1.6ms	1.6ms	1.6ms

A - This shows the voltage required to jump the spark plug gap. The voltage has increased to KV voltage as there are more winds in the secondary and the voltage increases to kilo volts.

B -  This is the time the voltage is flowing across the gap after the voltage has jumped the gap

C - This is the burn voltage after jumping the gap the voltage stays constant to burn the fuel mixture.

D - The end of spark and the voltage drops down.

E - Coil oscillation.

Everything looks normal in the pattern. There are more winding in the secondary so the voltage increases to kilo volts to jump the spark plug gap. !3 KV was required to jump the spark plug gap but the voltage drops down to a constant voltage to burn the air fuel mixture.

As we increased the rpm the Firing voltage increases but quickly drops down as the burn time increases to burn more of the air fuel mixture. I could not upload the video on blogger so i uploaded it on you tube and here is the link - http://www.youtube.com/watch?v=Az7xEolJ684

The firing voltage increases due to a large plug gap or beak in the plug leads. If the mixture is also lean the firing voltage will increase. Worn out spark plugs will also cause a high firing voltage. 

The firing voltage decreases when the plug gap is small. Rich mixtures also have low firing voltage.

Then with the engine stopped  we disconnected Cylinder 1 spark plug lead and shorted it to the engine with a jumper wire.

By this testing we saw that that the firing voltage decreased for cylinder 1 as we had grounded that spark plug wire to the engine. But the spark duration increased a little bit.

Ignition Secondary	CYL 1	CYL 2	CYL 3	CYL 4
Firing Voltage (KV)	4kV	8KV	8KV	8KV
Burn Time (ms)	5.9ms	3ms	3ms	3ms

Then we stopped the engine an attached a spark plug tester to one of the spark plug leads and grounded it to the engine.

The the video keeps getting deleted off blogger so i uploaded it on you tube and hers the link - http://www.youtube.com/watch?v=Tx52mes4qG8

From this pattern we can see how the firing voltage increases to jump the gap but the burn time is very little. As the gap increases the firing voltage increases.

The we removed the spark tester and got the engine back to normal and the engine is runnig fine.

Oxygen Sensors On Vehicle (WS6)

Oxygen Sensor On Vehicle

The oxygen sensor was located in the exhaust piping after the exhaust manifold before the catalytic converter. This oxygen sensor has 4 wires. This is a heated type Zirconium switching sensor. The wires were:

white - heater supply

black - signal

grey  - sensor ground

white with black strip - heater ground.

I back probed the signal wire on the oxygen sensor and connected the oscilloscope.

I started the engine and let it warm up 4 a bit to enter closed looped mode to see a cycling pattern. I Reved it to 2500RPM for about a minute and it went to closed loop and i could see it cycling.

The voltage went up to 0.9v highest and lowest went down to 0.2v. The average voltage is 0.5v.There was 15 cross counts in 10 seconds. Cross count are voltage high to low or low to high.The signal would not cycle properly if the sensor had a problem wit it. The pattern will be different.

Then with the engine heated up and the oxygen sensor in closed loop we recorded the pattern at idle.

The voltage goes up to 0.7v highest and lowest goes down to 0.2v.The average voltage is 0.35v. At idle cross counts decreased to 7 at 10seconds. The highest voltage is also low then at 2500 rpm because the mixture is leaner at idle than at 2500 RPM. The cross counts also decreased at idle because the revs are lower at idle so the emissions are lower so the oxygen sensor reads slower and then sends out signals slower therefore the cycle is slower.If the signal is not cycling normally there is a problem with the sensor due to contamination  or damage.

Then we made the oxygen sensor go rich by acceleration at short periods.

The signal went high to 0.9v showing a rich mixture.If the signal didn't go high the ecu would not know that the mixture is rich so  would richen the mixture more as it knows there is more air entering the engine. The ecu will think that there is more oxygen in the exhaust so it will richen the mixture more and do more adjustments. This would lead to high fuel consumption and high hydro carbons and unburnt fuel coming out of the exhaust.




We then make the oxygen sensor go lean by doing sudden deceleration. We ran the engine to about 3000RPM for a bit and then let the RPM drop suddenly.

The voltage drops down to 0.2v telling the mixture is lean. If the signal is not going low normally then there is a problem. The signal will be telling the ecu that the fuel mixture is still rich   and then the ecu will make the mixture more leaner. which will cause problems when the problem when the engine decelerates. 


We then measured the response time of the sensor to  know that the  sensor can quickly respond to changes in the exhaust gas. We did a sudden acceleration and recoreded the pattern and then looked at how quick it went from lean to rich. My time was set to 100ms per division.

It took 120ms to go from lean to rich and is within specifications. The sensor is working properly and is quick enough to respond to changes in the exhaust gas.


I conclude that the oxygen sensor is in good condition as the outputs are correct when we made a rich and lean condition. It also cycles correctly in closed loop. 0.2v for a lean mixture and 0.9 for a rich mixture. Also the response time is within specifications.

Zirconium have 2 electrodes which provide an output voltage corresponding in relation to the amount oxygen in the exhaust and amount of oxygen in the atmosphere. The inside of the measuring tube is connected to the atmosphere and the outside of the measuring tube where the exhaust gases travel. If more oxygen in the exhaust the voltage is low that is 0.2v and less oxygen in the exhaust giving a high voltage that is 0.9v. Thats how we get 0.2 to be a lean mixture and 0.9 to be a rich mixture.

Exhaust Gas Analysis (WS7)

Exaust Gas Analysis

We used a exhaust gas analyzer to do gas testing Honda civic 1992.

HC - means hydrocarbons - that is unburnt fuel caused by weak ignition spark, rich or lean air fuel mixture.

CO - Carbon monoxide - caused by a rich mixture , not enough oxygen.

Co2 - carbon dioxide - high percentage shows engine more efficient

02 - oxygen - shows air in exhaust. Caused by exhaust leak or lean mixture.

clean emissions :

 - HC under 100ppm (less is better)

 - CO under 0.1% (less is better)

 - CO2 over 13% (more is better)

 - O2 under 2% (less is usually better)

When the analyzer probe was sensing normal air  we got readings:

HC	CO	CO2	O2
0	0.003	0.01	20.84

We started the engine idling cold and got readings.

HC	CO	CO2	O2
413	1.633	14.83	0.72

This shows there is unburnt fuel in the exhaust and CO is high telling us the air fuel mixture is rich because the engine is cold and the ecu has made the mixture rich to heat up the engine. It is in open loop mode. The Co2 is also high telling the engine is running efficiently.

When the engine had warmed up the readings changed.

HC	CO	CO2	O2
48	0.089	15.33	0.43

This shows us that the engine has warmed up now and has gone to closed loop. The HC and CO has decreased telling us that the mixture is not rich anymore. CO2 has increased more telling the engine is running more efficiently. The fuel mixture is keeping stoichiometric to give out clean emission. 

When we increased the engine RPM to aobut 2500 we got readings.

HC	CO	CO2	O2
42	0.103	15.50	0.37

HC went down but the CO rises a little and oxygen drops a little. This tells us that the fuel mixture is bit rich then at idle. HC decreased a little which tells us that the fuel is getting burnt a little bit better than idle. CO2 is still high telling us engine is efficient. Emissions look pretty good.

Then we made the engine run rich by spraying in some propance gas. At idle we recorded the readings.

HC	CO	CO2	O2
2184	6.58	14.90	0.63

When we made the engine run rich HC and CO went up. There is a lot of unburnt fuel coming out the exhaust as there is not enough air at idle. CO increases as we have made the air fuel ratio rich.

Then we created an air leak to run the engine in a lean condition. The readings were recorded at idle.

HC	CO	CO2	O2
15	0.03	15.43	1.53

By making the engine run lean HC and CO decreases and O2 increased. CO deceasing telling us its a lean condition. HC decreased as theres is too much air and so more fuel gets burnt to compensate. O2 increases telling us that there is too much air and not enough fuel so excess unburnt oxygen comes out the exhaust.

We then accelerated the engine by blipping the throttle a few times and got readings.

HC	CO	CO2	O2
243	3.412	13.79	2.56

By blipping the throttle, the ecu makes the air fuel mixture rich as the engine is sucking more air in. As the engine gets rich CO increases. These is high HC and High O2 as well. This tells us that the spark was not strong enough to burn the fuel mixture thats why there is unburnt fuel and air in the exhaust. There was not enough time to burn all the fuel. 

Then we disconnected one spark plug and grounded it with a jumper wire to chassis. we got readings.

HC	CO	CO2	O2
1855	0.139	15.44	0.59

By this information HC is really high as one of the injectors were  disconnected so theres a lot of unburnt fuel coming out the exhaust.

Then we disconnected one of the connectors from the injectors

HC	CO	CO2	O2
34	0.007	11.22	6.30

By disconnecting one of the injectors we made the engine running like a lean condition. CO decreased telling us that its a lean mixture and there too much oxygen. HC decreased and oxygen highly increased telling us theres too much oxygen and not enough fuel.

We then returned the engine to good condition and everything in place.

Vehicles fitted with a catalytic converter has cleaner emissions as the 2 beds in the cat cleans emissions. HC, CO and oxides of nitrogen go into the cat and come out as carbon dioxide, water and nitrogen. Light off point means when the cat starts to work and clean emissions. It needs to reach a certain temperature to start working.

On oxygen sensors some of them have 4 or 5 wires, which are also for the heater. Because the oxygen sensor needs to be hot to work, the heater assists in heating up the oxygen sensor so its goes into closed loop quicker.Wires can be signal, signal ground, heater supply and heater ground.