SMAN's Dyno Disater - Updated - Electrical Issues

[sman]

How would I check to see if the computer is sending the signal to the coil? Just hook a voltmeter to it?

[1BADAIR]

did that blink normal or just randomly?

[sman]

My house and shop are all the way across town from each other, I've already left. But would that be a way to test If the pcm was sending the signal? Or its it not just electrical current that triggers the coil? Don't want to mess up the computer testing this.

Anyone have a 99 v8/a4 pcm I could try in my car too see if that's the problem?

[1BADAIR]

what code is it?
i think trying a pcm is next

[sman]

P0355 - ignition coil 5 - primary/secondary circuit failure. I load tested all the wires so that's the only thing I can think of.

[sman]

Would A pcm from a vette work? 98 a4

[sman]

New development, if I clear the code or unhook the battery, the code returns immediately, like without even starting the car. As soon as I turn the key on, it throws it. I almost think it has to be the computer.

[1BADAIR]

97 98 wont work

[BigJeffSS]

Yeah 99 and up they changed somethings. If 98 would have worked I would have offered mine up.

If i was you I would inspect the terminals through the wiring harness. It is a known problem for the terminals to lose connection strength over time. In other words it isn't making a strong connection with the other terminals. The terminals in the PCM are also known to become loose and cause issues. Also make sure you inspect all of the connections and terminals that are part of the coil harness. Also look for grounding out issues or shorting wires in the harness. Tomorrow at work I will look up the exact flow chart for repairing this problem if you want it. Here is a general troubleshooting flow chart that is not from GM's SPO site but it should help some.

http://www.gearchatter.com/viewtopic9357.php

[sman]

I followed the chart(already had it from gm dealerworld) im at the replace pcm step.

HOWEVER.... When I test the signal circuit for voltage(should be 1v per the how to thing) Ive got 0. So I assume same case, good continuity in the wire, ran an old school turn signal bulb through the wire, so I know its good, just looks like the pcm isnt sending the trigger signal.

[sman]

Anyone have a pcm with VATs disabled so I could try before spending the $ on a new one?

[BigJeffSS]

Did you inspect the terminals in the PCM connector? We replace those terminals all the time out here at the country club. (GM guys know where that is) You can pass a continuity test yet still have bad terminals they lose strength over time and can longer make contact with the connectors in the PCM. Also when you checked the wires to the PCM did you also check them to ground/short at the same time. If the wire is shorted it will also cause a 0v reading. I would say if you did all the checks then you're on the right track replacing the PCM since that circuit is dead.

[sman]

The terminal looked good, just as all the other ones around it, so im assuming its ok? To check for short to ground its just a continuity test but test my trigger wire for continuity to ground?

[BigJeffSS]

Don't assume the terminal is good look inside it there should be a small metal tab sticking out. I have a few extra terminals at home if you want to change it.

Have you tried to do the bulb test again sorry but I don’t recommend using a bulb to test that circuit as it is a low voltage circuit you’re putting a bulb across. Now I can't figure out why it would trigger the light bulb and not have any voltage on the IC circuit. I would check the frequency of the ignition circuit by using use a good DVOM that can read frequency. I have one if you need to borrow it.

To check the wires for grounding unhook both the PCM and coil connectors. I would unhook all the coils on that side since they share the same ground and low reference circuits. Now just go through and check each wire off the coil connector with one DVOM lead to the terminal and the other lead to ground. They shouldn't have resistance except the ground wire and that should be low resistance. Since you’re at it I would also check all the PCM grounds to make sure they all have low resistance.

Jeff

[sman]

Jeff, you just wanna come over and help? Haha. I don't have anything to read ffrequency.