WS3 Oscilloscope patterns

Map Sensor on a 4AFE

On the image of the Map sensor on a scope you can see the engine being revved, as the engine Rpm increases you can see on the graph the increase in voltage, this is because there is not as much vacuum as there is at idle,  looking at the first increase, before the increase is when the engine is at idle and there is a good vacuum, as the engine rpm increase you can see the voltage rise as there becomes less vacuum, as the rpm decreases vacuum returns, this is what gives the graph its mountainous shape.

If a high resistance occurs in one of the wires, like the earth wire, this would make the sensor operate incorrectly. There could be many symptoms that occur from this such as, rich or lean fuel mixture, rough idle or hesitation. These could occur from a bad earth connection either at the sensor or further down where it connects to earth. This would cause the unit to malfunction as the circuit would not be complete with no earth.   

With no resistance in his wire the output voltage would be expected to be 4.5v but if you add the extra resistance into the wire this would change, Vd = Vin(R1/R1+R2)



Throttle Position Sensor

This is the image I read from the tps sensor on a nissan aveniar. As you can see from the image the voltage increases when the throttle is moved to the fully open position. when the throttle is fully open we got a reading close to 5v.As you can see on the graph it starts off at idle (the lowest voltage on the graph) and is slowly opened to fully open, once the fully open position was reached we then slowly closed the throttle and returned it to the idle position.

The TPS is sensitive to heat, moisture and vibration leading to the failure of some units. This could cause the vehicle to have poor idle control, high idle rpm or even an engine misfire.This could result in the pick up arm failing to make contact with the signal wire which would result in the voltage suddenly dropping to 0v.








 RPM Sensor

This is one of the images of the rpm sensor i took, This was a video put I was not able to post it on blogger for some reason. As you can see from the image the voltage increases at the engine is revved higher, this was because we used a magnetic pickup sensor which creates an AC voltage and the faster the pick up turns the higher the voltage it creates.

A fault that could happen with one of these sensor is a loss of power, no power circuit, this could be due to many things such as positive side has become disconnected from the circuit as these sensor create their own voltage. Another problem could be in the sensor its self and the gap inside could be too large creating a week voltage.


 Oxy Sensor

This is a reading from my 02 sensor in closed loop. As you can see the engine cycling  between rich and lean, this is so it can control the emissions. When the voltage increased this shows the engine going rich and when you see it lower it shows the engine running lean.

Problems with 02 sensor are very common, if an 02 sensor is faulty the vehicles emissions would be greatly increased as the engine would not know whether to cycle or not  










Injector pattern - civic


IAT sensor - civic


MAF Sensor

At the start of the pattern you can see the voltage at roughly 1v, As engine load is increased the voltage rises to 2v, and when engine is returned to idle position the voltage quickly decreases. A common problem with MAF Sensors is that they get contaminated on the hot wire, this is mostly due to people putting pod filters on cars with a MAF sensor. This could increases the resistance of the hot wire and make the engine perform poorly