In my ongoing nightmare to figure out why my car won't start I've again traced the FSM flowchart to the conclusion that I have a faulty ignition module. I just bought a new one, which means either it's also bad or my car is somehow cooking them.

One other thing occurred to me: I have a 1993 but have upgraded to the 1995 Optispark. What is the difference between the ignition modules in the newer cars? My computer is still from 1993 so I assume that's the one I need, but I'm starting to wonder...

1993 part : ACDELCO Part # D1971A {#10483131}

1995 part : ACDELCO Part # D1986A {#10483139}

 

As long as you have the harness wired right there is no difference between optis. A 95 PCM will not work in a 93 due to the crank trigger issue along with the fact it is a PCM not ECM. I would double check your harness and wiring to the opti and ICM.

 

I've checked all the wiring for continuity and shorts. It all checks out ok (it's a 3 yr old painless harness). Still inspecting for any loose grounds.

Please elaborate on the comment about the 95 pcm not working...one of the options I'm considering at this point is buying a '94+ engine computer and harness and updating everything. They're easier to program and there is more diagnostic capability. Doesn't the crank trigger come from the optispark?

Oh, and the '95 opti on the car worked fine, but I replaced it with an MSD. It seemed possible that MSD did something year-specific.

 

I'm confused, there is a difference between 92/93 Optis and 94-96 Optis - the pin coming off the cam is different I think. I thought that's why everyone sells 2 different Optis, MSD, Dynaspark, etc. For example go look at www.dynaspark.net - you can there are physical differences between the Gen I/II

So I don't see how you are running the later Opti on a 93, I was told that wouldn't work.

ScaryFast - I just went through a similar problem. Was getting a Code 42 and no start. I put a new ignition module on and still kept getting the code.

What I "think" has fixed mine is I redid the ignition ground wire that runs to the block - you'll see it right above the coil. It looked perfectly fine from the outside but I took it off and it had a lot of corrosion on the connector and the block. So I took a dremel and cleaned up the block surface and just put a new flat-face connector on it. The factory connector has raised "teeth" on it and I believe that's what allowed moisture to get underneath there and so it corroded. Make sure to double-check that - if I had taken 1 minute to check it I could have saved myself hours of headache. I was going to post pictures here on the forum but I lost em'.

Also - how is your voltage? I had an alternator problem and the code 42 magically reappeared, and then as soon as fixed that problem it seemed to go away. That "might" be because of a bad ECM, I'm not so sure mine is operating at 100% but I'm going to give it some more time. So you very well could have a bad ECM.

Anyway, double-check that ground if you hadn't already.

And I think you are going to find that swapping to a 95 PCM is probably a lot of trouble. You'll also get a blinking SYS light on the dash because the CCM is expecting a 93' computer, not 95 - I see this problem now on my 96 which has a 95 PCM.

 

I'm running a 96 opti in my '93. You just need to change the timing cover and harness. You still use the '93 ICM. If your ICM and wiring are both good, then it is very likely the ECM. Good luck finding one.

 

Like Lichen said, I updated the timing cover and timing gear set to allow it. I highly suggest this...it's not expensive and from reading your other posts you have the ability to do this. Next time you have the front of the motor of go ahead and do it, but don't waste your time if things are running fine at this moment. I have a document with the parts list and instructions if you're curious. It's around on the forum, too but I saved a MS word version.

I've gone through EVERYTHING on this car to find the problem. All FSM tests point to the ICM being bad, so I put a new one on. Therefore that part was somehow bad, or it's in the wiring. I've gone through every related wire and checked for continuity between the related components, as well as shorts to Vbatt and ground. My next step is to verify that all my grounds are good, that's a helpful tip above. I'll definately check it.

Voltage is good. I keep charging the battery. The alternator worked up until the car died, so I don't think it's the root cause.

It's a race car, so there are no lights on the dash and I'm not worried about codes. I've gone through the '94+ pinout and I only need 51 of 83 circuits. I have to program out the MAF sensor, and possibly the downstream O2 sensors (my car only has 2). I am considering splicing on the new connectors to my harness, but since the harness may be the culprit I may bite the bullet and have a custom harness built with only the circuits I need. But I HATE buying parts for the car hoping they fix an unidentified problem...

I had the ECM bench tested with an actual opti, coil, and working ICM. It tested fine. However, that's not always difinitive. My '93 ECM is a POS anyway, so upgrading will help with that option also. But it's an expensive option to *maybe* fix the issue.

Thanks again for the suggestions...

 

Well yes it is possible to re pin and put the PCM in. I would still check the pin out on the opti and make sure it goes to the correct pins on the plug. Check for spark at the coil. The crank trigger is inside the cover near the opti IIRC and requires another harness plug to it. Look at a 95,96 vette to see it. I believe it is on the pass side. When did it run last and what did you do prior to it not starting?

 

OK thanks for the info on the Opti - luckily my car has a new MSD so hopefully I won't have to be dealing with it for a while.

It sounds like you have covered everything so if the car is a race car then I think I would go up to the 94/95 PCM and just get another harness.

My 96' has a 95 PCM and I love the ease of flashing it, it's hard to beat. I wouldn't mind going up to a PCM on this 93 to tell you the truth, these ECM's and PROM'S are a PITA.

 

Redeasy, this has piqued my interest. Is there a difference in the plug along the intake that goes to the optispark between the older and newer cars? I had a jumper harness from that connector to the '95 stock optispark I had. Perhaps the pinout to the MSD is different?

I'll check the two wiring diagrams...

Also, so the newer cars have a crank sensor? So I'll have to add this?

 

96' and later have the crank sensor, 95 and earlier don't, the crank sensor has to be there for OBD II

 

Good info I was not sure if both years had it or not. So it appears a 95 PCM might be a good choice is it plug and play? I suppose not due to the MAF.

 

That is why I mentioned it. IIRC there are 4 wires and wether or not they go to the same wires in the plug by the intake I could not tell you on a 95 opti.

 

Scary - please let me know if you figure out the no start - my car just left me stranded 30 minutes ago!!!!!!!!!!!!!!!!!!

1 mile from the house too!!!!!!

 

I think it's close to plug-n-play but my concern is all the little sensors and connections, etc. If someone has done this I would LOVE to know.

-edit- HMMMM was just thinking, with the C4 Gathering going on, Gordon Killebrew is doing his "drive through troubleshooting" tomorrow. If anyone knows the answer to the ECM/PCM question it's probably him so I'll ask him tomorrow.

If I can get my car TO the event I'm going to have him look at it. Otherwise I'm going to try to bribe him to come by my house. . . . . .

 

Awesome, so i don't need the crank sensor.

My tuner said he can tune out the MAF, no worries there.

All the sensors are compatible. I'm going through the pinouts between the '94-95 and '92-93 computers. If anyone wants a copy when i'm done I'll .pdf it. I'm cross referencing the pin numbers between the two to see what's missing or extra.

I confirmed that the 94 and 95 PCM's are the same part number.

RUK can you take a photo of that ground, I can't find the one near the coil. And if you do talk to Gordon tomorrow, ask what else could be causing no spark if Opti, ECM, ICM, and coil are all brand new? Also, I know he takes phone calls for cash, see if he thinks he can help me and I'll call him...

THANKS!

 

I just got off the phone with him.

First thing he asked was what Opti I had, when I told him MSD he wasn't too happy, he said he has seen a lot of those that are bad right from the start.

I have a Tech 1 (on loan from previoius owner) but he said to pull the CCM codes by grounding pins A/G on the ALDL. When I asked him about the Tech 1 he said they are not as reliable and actually don't clear codes all the way. He said the CCM stores the codes for 50 ignition cycles, even with battery disconnect and Tech 1 clear-out, which I didn't know. So he told me to check for those codes in the CCM then clear em' out and give it a shot. I'm gonnna head over in just a few minutes.

If I can't get it home I'm gonna push it up the street to the Shell and he's gonna take a look at it on his way up tomorrow morning. So I'll let you know!!!!!!!!!

-edit- Oh and on the ground I'll try to take a pic but you really can't miss it - it's right above the coil - should be a black ground wire running out of the ignition harness - that ground should be screwed into the block right above the coil. The ground connector is one of those connectors that kind of has "teeth" on it, kind of in a star pattern.

Also - I'm not 100% but I'm pretty sure if you disconnect the MAF on a MAF car then yes you get a code but the car will then run in Speed Density mode, not limp mode. So try that as well. I haven't seen anything in Tunercat that let's you tune out the MAF but I've never really looked for that either.

 

One important fact. If you switch to a newer style opti, be sure that you get the timing chain cover and harness from a '95. Something changed in the '96. I can't remember what, but you can use the '96 opti, but the other parts must be from a '95.

 

The reluctor for the crank sensor?

 

Correct - the 96 has a different timing cover to account for the crankshaft sensor, which is required for OBD II (I think it helps detect misfires and therefore emissions problems more easily from what I vaguely remember). I can't remember if the reluctor ring actually affected the design of the timing cover per se or not but I do remember the 96' cover has a little boss on it where the crankshaft sensor goes.

From talking to Gordon today it sounds like my MSD opti (put on brand new by previous owner just a few months ago) might be the cause of my problems. I originally suspected the Code 42 might be caused by it but then I discounted that since the FSM doesn't state that as a potential culprit for this problem so I went down other paths, like buying a new ignition module for example.

-edit- Oh and Scary - Gordon is meeting me at 7:30 in the morning at the Shell where we pushed the car to tonight. He seems to initially be leaning to the Opti but I'll update this post tomorrow with what he says. I'm also gonna pick his brain on what his thoughts are regarding the switch to the PCM from ECM.

 

Scary - one thing I was thinking about - I assume you have ruled out a fuel problem? In other words you have fuel pressure?

Also please get me the parts list you mention above regarding the Opti swap, I may be doing this.

-edit- Scary talked to Gordon this morning - he said the ground I'm talking about right there by the coil is only for the tach.