Model: 4A-FE
Fuel Injector
Locate and record voltage to the fuel injector - 14.44v
We would test the supply voltage to the injector because if there is no voltage supply there is no way for the injector to switch or to operate.
If there is a lower voltage at the injector, this could mean there is a resistance between the battery and the injector. This could mean the injector will not fully open therefore the right amount of fuel will not enter.
Reference voltage at TPS sensor
The voltage reading we received was 4.9v
The purpose of the reference voltage on the TPS sensor is for the ecu to look at and determine where the throttle position is, the reference voltage is the tps sensor at rest.
If the voltage is too low,the incorrect votlage would be sent to the ecu
Ground at TPS sensor
ground reading = 4.3 - 4.5mv
This reading shows that there is a very good ground as there is very little voltage drop, when measuring the ground wire you want the lowest voltage possible, an acceptable reading for this tps sensor would have been 0.05v
If there is a bad ground then the ECU would get odd readings from the tps sensor as the circuit would not be complete, therefore creating an open circuit.
Throttle Position Sensor return/output
output at rest - 517mv
output at half open - 2.2v
output at fully open - 3.8v
When slowly opening the throttle there where no sudden jumps in voltage.
The colour of the idle switch is blue
The tps sensor is just a variable resistor, as the throttle is opened the voltage increases as the resistance decreases so as the voltage changes the output voltage gets sent to the ECU which in turn adjusts all of the necessary adjustments.
Engine Coolant Temperature
ignition on engine off - 1.4v
at this point the engine is warming up.
With the engine warmed up the voltage changed to 1v
The ECT is just a resistor which changes with heat, the hotter is gets the higher the resistance, therefore as an engine is warming up the voltage will be higher than it is if it was hot or at operating temperature.
If there was a resistance in the wire the ecu would think the engine is at operating temprature quicker.
Ground Coolant Temperature Sensor
With the engine running the ground voltage was .006v, this tells us that there is a very good ground to the ecu, is is important to measure this because if there is a bad ground the ecu would not be receiving the right voltages.
RPM Sensor or Crank Position Sensor (CKP)
With the engine running we got a voltage of 0.23v Ac
With the engine RPM increased to 2500rpm we got a reading of 0.45v Ac
With the engine returned to idle speed we switched the mulitmeter to Dc volts and got a reading of 0.71v Dc
Then with the engine RPM back to 2500 RPM we got a reading of 0.71v Dc
With the engine returned to idle we switched the multimeter to Hz and got a reading of 32mHz
Then with the engine RPM back to 2500 RPM we got a reading of 85mHz
Hz showed the RPM sensor working much better than Dc volts
MAP or MAF Sensor
