MAP Sensor
This waveform was taken during a sharp acceleration. The voltage increases when more throttle is applied. Where the waveform starts is point A that is idling voltage. where it increases is when more throttle is applied and the end on the waveform is idling voltage again.
A fault to stop the MAP sensor working could be a broken connection, it could be open circuit inside the MAP sensor. Could have excessive resistance in the wiring loom. There could be a wiring fault when it was connected.
MAF sensor
The beginning for the waveform point (A) is the MAF at idle. at point B when it is increasing this is when the throttle was applied and more air was allowed into the engine.At point C it would be back to idle voltage.An electrical fault could be the wire not heating up and resistance doesnt change so voltage would always be the same.In this situation the voltage would always be 1.7V and would not change. The effect of this would be the car would run in limp home mode and idle will fluctuate. The graph would look like a straight line with no movement from idle voltage.
TPS .
We didnt have a linear type so we used a potentiometer type. point A is 0.5V whcih is idle voltage. It slowly increases as more throttle is applied this is because resistance decreases as more throttle is applied. This is a variable resistor. The problem could be excessive resistance in the earth wire. So there would be less voltage at the TPS. So the ECU would not know how much the throttle was applied. So the engine would run rich.
ECT
This graph shows what happens to the ECT. It would be difficult to get a waveform showing the voltage changing. The ECT is a NTC thermistor. This means as temprature increasing resitance decreases. A problem again could be excessive resistance so the ECU would not recieve the correct voltage and would not know if the engine is hot or cold. If the ECT voltage didnt change stayed at 5V the engine would be constantly rich.
IAT
This graph shows that the IAT is NTC thermistor. resistance decreases with TEmprature. It would be difficult to get a waveform showing the voltage changing. Again the problem could be excessive ressistance within the circuit. This would mean the ECU would get incorrect signal voltage. This is how the ECU knows it is a cold start by comparing voltage to the ECT. if there was excessive ressitance the voltage would be lower.
MAF sensor
The beginning for the waveform point (A) is the MAF at idle. at point B when it is increasing this is when the throttle was applied and more air was allowed into the engine.At point C it would be back to idle voltage.An electrical fault could be the wire not heating up and resistance doesnt change so voltage would always be the same.In this situation the voltage would always be 1.7V and would not change. The effect of this would be the car would run in limp home mode and idle will fluctuate. The graph would look like a straight line with no movement from idle voltage.
TPS .
We didnt have a linear type so we used a potentiometer type. point A is 0.5V whcih is idle voltage. It slowly increases as more throttle is applied this is because resistance decreases as more throttle is applied. This is a variable resistor. The problem could be excessive resistance in the earth wire. So there would be less voltage at the TPS. So the ECU would not know how much the throttle was applied. So the engine would run rich.
ECT
This graph shows what happens to the ECT. It would be difficult to get a waveform showing the voltage changing. The ECT is a NTC thermistor. This means as temprature increasing resitance decreases. A problem again could be excessive resistance so the ECU would not recieve the correct voltage and would not know if the engine is hot or cold. If the ECT voltage didnt change stayed at 5V the engine would be constantly rich.IAT
This graph shows that the IAT is NTC thermistor. resistance decreases with TEmprature. It would be difficult to get a waveform showing the voltage changing. Again the problem could be excessive ressistance within the circuit. This would mean the ECU would get incorrect signal voltage. This is how the ECU knows it is a cold start by comparing voltage to the ECT. if there was excessive ressitance the voltage would be lower.
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