QuestionQUESTION: My wifes van started acting up suddenly one day on her way home from work. She first noticed a miss in the engine and then when she came to a steep hill it would barely pull it. I took it to a repair shop and they told me it was a clogged fuel filter so he changed it but it did not improve. He then said the catalytic converter was clogged so I took it and had the converter removed but it did not improve. Since then I have been doing alot of research trying to figure out what is the problem. I found an article that said to check the voltage on the Throttle Position Sensor so I did and it pegged the multimeter and the article said it was only supposed to be 5 volts. To make sure I was doing it right I went to my local auto parts store and had them to use their machine to check what code it was showing and it said voltage too high to Throttle Position Sensor. Now I don't know where to go from here.
Thanks for your help, Steve G
ANSWER: HI Steve,
The 5 volt supply is located at pin 61 of the pcm on a violet/white wire which goes to a aplice near the speed control unit and transmission dipstick and from there three violet/white wires branch off to the throttle position sensor, the manifold absolute pressure sensor and the AC pressure sensor. None of these devices also carry either 8 or 12V so somewhere along those wires I listed there is some melting of insulation of the wire harness which has produced a short between a violet/white wire and some other wire carrying a higher voltage. It would probably be in a harness near the exhaust manifold due to higher temps nearby to that. So go to each of the three devices and look along the harness for a melt.
Please 'rate' my answer (see below).
Thanks,
Roland
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QUESTION: All three of the devices you mentioned has a high voltage but I have checked all the wires and there is no melting of wires or any other damage. I don't know where to go from here.
ANSWER: Hi Steve,
The question would be is whether the hige voltage on pin 61 is due to a short in the wiring or a faulty pcm which is where the 5v supply is generated. I think the way you could find out would be as follows:
remove both pcm plugs so you can simply check out the pcm itself,
then jump 12v to pin 20 and to pin 46 of the pcm sockets,
then jump wires from pin 10 and 50 of the pcm sockets,
Then measure the voltage on pin 61 to see whether it is 5v or not.
If it is 5v then the problem is in the wiring harness. If is high (identical to what you have measured with the plugs inserted) then the problem is the pcm.
Please 'rate' my answer (see below). I would appreciate your giving me a 'nomination'.
Roland
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QUESTION: I did as you said and pin 61 had around 6 volts but when I checked the voltage on the two jumpers one of them showed no voltage (the one from pin 10 to pin 50)
AnswerHi Steve,
I should have noted that 10 and 50 are ground wires on the plug so of course you got no voltage reading on those. How does the 6v on pin 61 compare with what you had been seeing at the the sensor plugs? If the same then there is nothing wrong with the wires, and the 6v is a bit high but would likely be acceptable. If you saw 8 to 12v at the sensors then there is a short from somewhere in the harness over to the violet/white wire that supplies pin 3 the TPS and you will need flex the harness to try and find where it is located and then repair the short.
Please "rate' my answer (see PS below). I would particularly appreciate a nomination to be 'expert of the month'.
Thanks,
Roland
