QuestionHey again. Ok today I went out, and it started, but I had to pump the gas,and really try to get it started, previously, it started up normal, when it did. Went to advance auto, code reader said p0120 tps/pedal position sensor a circuit malfunction, got back home, wouldnt start again. Could this be the whole problem, or is this another problem? I again thank you for your help, and patience!
AnswerHi Ken,
The name implies a problem with the TPS or its circuit. It is mounted on the throttle body, on the opposite end of the throttle valve rod from the throttle lever. It is basically a variable voltage divider that uses a 5V supply, and then puts out a voltage between 0 and 5 volts approx. depending upon the throttle position on it 'signal' wire. So you will want to verify the three wires, that there is 5v on pin 1 wire (violet/white), and that as you move the trottle that the signal wire voltage varies smoothly with no discontinuities. The violet white is on pin 61, the sensor ground wire (pin 3 black/light blue) in on 43, and the signal wire (pin 2 orange/dark blue) you should see the varying voltage eiter at the sensor end or at the pcm end at pin 35 of the other 40-pin plug. You will need to either probe where the wire attaches to the plug with a needle tip on you voltmeter, or penertrate the wire insultation with a needle to touch the conductor to do these measurement. Use the pin 3 wire as your voltmeter ground. First remove all three plugs and verify continuity, and shake the harnesses to observe for possible 'opens' or grounds of the wires.
There is every reason to believe a faulty TPS or its wiring is why you can't get reliable starts. Look particularly for flakiness when shaking the wire harness while doing any of the continuity/voltage tests.
Roland
