Guest47904

I guess the first thing you didn't soak in was if it does NOT have an external fault. You or someone still feels it's external. Otherwise they wouldn't be replacing the three foot section of wire to the opti.

The other thing is if it does not have an external fault, it couldn't fry the PCM. Remember, the PCM is like any other solid state device and it can go bad like a light bulb. Working one minute and not working the next. However, lets get back to the harness.

You said someone is replacing the 3 foot pigtail to the opti? But that's only a portion of the wiring between the PCM and the opti. There is still about 10 more feet other than that 3 foot piece. And it has 2 more connections that could be faulty. Much less the wiring between those 2 connectors.

I fail to understand why anyone would simply replace that piece without actually taking some simple measurements. But I'm **** about finding the defect BEFORE shotgunning parts. Comes from trying to run a repair business in which we can't return parts once we buy them I guess.

JAKEJR

FSM is the Factory Service Manual. Actually two manuals; GM's official offering.

Jake

West Point Rocks! Nation's TOP COLLEGE per Forbes Magazine!! Graduation Day Parade 20 May 2010!!!

texas97z

Thanks Jake for the deffinition.

Speedy- I here what you are saying about simply checking the harness rather than buying parts. I have the same philosophy of checking everything possible before spending money, but if he is getting no where and decides that's what he wants to do, itis what it is I guess. He has had quite a few problems with this car and is probably just wanting to solve it how he knows how.

I get you on the pcm going bad like a light bulb, sometimes it just happens. I let a guy borrow a spare I had and am trying to get it back to let him borrow it to see if that solves it since we know that the ICM is not getting a signal from PCM.

texas97z

I went over there today for a few hours and this is what we got.

I checked the resistance of the opti pigtail from end to end and from where the pigtail connects to the harness. Moved and bent, all were no good, no high resistance readings. So pigtail and immediatley after pigtail are not the problem.

Checked the ICM wires : Pink 12v, Black ground, Green 7.26v (should be 12 right), and white 0.2v.

So pulled the connector at the pcm and measured resistance to the connector for the white wire at the ICM, no problems there. Just to double check measured voltage out of the computer and it was same 0.2v.

Just to put it out of his mind, he did get a PCM from Brian at PCMforless and that made no difference. Car would start after 10 minutes of cranking, run for 15 min, then die and would not start again.

Measured the ac volts coming out of the opti at the pig tail (couldn't find what they were supposed to be) A 2v, B 10.7v, C 18-21v, D ground. Not even sure if this helps any but I figure the more info I can give, the more help you guys can be.

0 volts on white signal wire from pcm, all other syptoms as well, this opti no good too? It's under waranty so not that big a deal. Just stinks that he can't drive his car.

Thanks as always for the help,
Josh

Guest47904

The green wire going to the ICM should be checked for 12 volts with the wire DISCONNECTED and KOEO. The ICM could be loading the 12 volts down on the green wire but more about that in minute. It's not entirely clear what the green wire should be when it's connected to the ICM with KOEO.

The white wire going to the ICM should be checked for 1 - 4 volts connected while the engine is cranking. Either meter is set to DC scale showing min-max or set to AC.

Now let's get something straight. There is NO AC signal coming out of the opti. There is a 12 volt supply on C and the reference that may not be directly to ground on D going IN to the opti.

A and B terminals have a 5 volt DC square wave coming out of them when the engine is rotating. If it is not rotating, the A and B terminals could be at 5 volts or could be at 0 volts DC depending on where the shutter wheel has stopped inside the opti.

Here is where the confusing part comes in. The PCM uses the feedback signal from the opti (low res A terminal) to calculate spark timing. The PCM then pulses the IC white wire signal when it fires the ignition. The confusing part is whether the PCM will drop the IC signal to the ICM if it looses the opti signal. However we do know that if the feedback signals are lost from the opti, it will set a code.

Therefore if you suspect the opti feedback signals are the cause of the loss of the IC signal on the white wire to the ICM. There would have to be a code set for the loss of that feedback signal.

The ICM could be defective and sinking the white wire signal to ground. If the signal is on the white wire when it is disconnected from the ICM and engine cranking but not there when it is connected to the ICM, then it may indicate the ICM is defective.

texas97z

It was checked while someone was cranking, it was set to AC, and ICM was unplugged which is the same as shoebox and the sticky on this threads says to do. I checked it at the same time at the pcm's connector(black 5 pinout) to double check and there was nothing coming from there either.

I wasn't sure what scale to check the opti signals on. Just trying to gather some info rather than none. Searched on here but didn't find anything that said, if checking this do this. I am sure it is here, I just didn't see it.

ICM was not plugged in during test, and is a brand new peice anyway since he tried that too. But since it wasn't plugged in then that eliminates the ICM as possibly grounding out the IC signal.

It still has the same two codes from earlier 1352,0732, just no new codes is what I was getting at.

Guest47904

There are no 1352 or 732 codes buddy. But I did find this

To which I replied this

Now for the most important thing that I read in the GM shop manual is this:
If a DTC1351 is set with the DTC372. And no external fault can be found, replace the PCM.[/QUOTE]


So the question should only be: Is there an external fault or not????? So are you saying the green wire at the ICM had 7 volts on it but was NOT plugged in?

texas97z

Yeah typo, I meant still same codes just nothing new.

The green wire was tested plugged in and only getting 7 volts where as the pink was 12 on the dot.

Guest47904

What's the voltage across the battery with everything off AND what is it when the engine is cranking?

texas97z

everything off it was 12, never measured it cranking. The battery is toast though. Won't hold a charge for more than a few cranks, then dead and back to the charger it goes. I am sure all of this cranking and no alternator time to re charge since it won't run has been hard on it.

I think you are pointing out that the voltage may be low because the battery is not holding full charge, at least that is what I was thinking when I saw the battery go dead after 3 cranks it went from 12 to 8.

The place he got the opti from is sending him a new one to warranty this one out since all of these new syptoms(once the backfire went away) only started with this opti(no tach, very hard start thn die after 15 min, etc). Nothing else was changed at that time, only the opti and prior to the change everything worked good, just backfired. Now, new ICM, coil, even the PCM was swapped with a new one from PCMforless still no start.

Even with trouble shooting seems to point at the opti since none of the other things had any effect positive or negative on the outcome.

Speedy thanks for your thoughts/help, I have been listening to what you were saying and when I went over there to try and help him I have everytime checked what you suggested. Just wish I had known about the DC values on the opti harness last time I was there. I am going to go over there when the new opti gets to him this next week and stick around the whole time to make sure it goes on right and car starts before I head home.

Guest47904

good luck to you

texas97z

Car is alive and well as of yesterday!!! We swapped out the opti with another brand new one and car ran and idle great with no hard start for or backfire 20 minutes. When I left it was still running great.

Speedy, Fred, and Jake- He and I both appreciate the help with getting this car back on the road.

JAKEJR

WOW! Congrats on solving your issue.

Be sure to give us an up-date after a few days of driving to car just so we'll know that all's still well.

Jake

texas97z

Wow indeed, four brand new opti's in 3 months with no contact with water or anything else. I will indeed if I hear from him. Thanks again,

Josh