Chart of Inputs and Outputs

Chart of Inputs and Outputs

  

Measure the signals with a multimeter, set to the right setting, and record in the boxes.

Coolant Temperature (THW or ECT) DC volts	Cold engine 2.5v	Warmed-up engine 0.403v
Throttle Position Sensor DC volts	Closed throttle 0.404v	Open throttle 3.725v
Crank or RPM sensor AC volts and Hertz	Idle rpm 0.952v / 0.042KHz	2500 rpm 2.183v / 0.082KHz
MAP sensor DC volts	Idle vacuum 1.409v	No vacuum or key on engine off 3.649v
Air Temperature (THA or IAT) DC volts	Cold engine 2.398v	Warmed-up engine 2.089v
Throttle Position Switch (Idle and/or WOT) DC volts	Closed throttle 0v	Open throttle 12.79v
CAM sensor AC volts & Hertz	Idle rpm 104.4mv / 0.134KHz	2500 rpm 176.5mv / 0.246KHz
Fuel Injector Duty cycle %	Idle 5.7%	Acceleration 12.6%
Idle Air Control Duty cycle %	Idle 66.5%	Cranking or 2500 55.7%

ECT Sensor  

The first sensor I tested was the Engine Coolant Temperature (ECT) because it had to be checked while the engine temperature was cold.
The ECT sensor is used by the ECU to determine what the engine temperature is. The ECU uses this information to calculate proper fuel delivery and ignition timing. The ECT sensor is a thermistor type sensor (the electrical resistance of the sensor decreases as the temperature increases). The ECU sends a reference voltage to the sensor usually of 4 volts. As the engine coolant temperature warms up the electrical resistance across the sensor decreases to about 0.2v. The computer then uses this reading to determine the temperature of the engine by reading the voltage across the sensor. If the engine is cold the ECU will be in open loop mode keeping the injector spray time open longer to spray more fuel because when the cylinder walls inside the combustion chamber are cold fuel condensors to the walls and isnt burnt therefore more fuel is injected to combust and get the engine up to opertaing tempertaure of about 45 degree celcius (warm). The ECU will ignore feedback signals from the ECT and o2 sensor until operating temperatures is reached.
How to do test:
We did test using oscilliscopes, when the engine was cold and while warmed up. The engine has to be turned on and running at idle. The black lead of the scope has to be connected to a good earth and the red lead to the engine coolant signal wire from the sensor. (On this engine there is an outboard box to connect the scope probes to and get a signal). The scope has to be set to DC volts by clicking function then scope and then changing its settings to DC volts. The scope then displays a wave form on the screen and voltage reading and time.


Results: 
The results i got when the engine was cold was 2.5 V and 0.4 V when the engine was warm. These results show that the sensor is working ok. A sensor that wasn't working ok would read a high voltage while the engine was warm. 


TPS Sensor


Theory information: 
The TPS Sensor (Throttle Position Sensor) is a sensor used to monitor the position of the throttle. The sensor is usually a Potentiometer, and therefore provides a variable resistance dependent upon the position of the throttle. The sensor is used by the ECU as an input to its control system. The sensor tells the ECU how open or closed the throttle is so the ECU can provide the correct fuel to go with the air into the combustion chamber.


How to test this sensor:
To test this sensor use a multi-meter set to DC Volts. Touch the red probe of the meter to the TPS signal wire and the black probe to a good earth. Turn the Key ON Engine OFF. 


Results:
Closed throttle i got a reading of 0.4v and as I started opening the throttle the voltage starts increasing. Open throttle I got a reading of 3.7v.