Ignition Control Module Help! Part needed 95 Supercharged

So, I have gone through a few ICMs, brand new ones from Rockauto gave out in a matter of weeks… I am now back to using the original ICM, which has problems when car heats up to running temps…
Does anyone have a solution to this? Is there anyone selling a supercharged ICM, which is reliable?
How did you guys solve this issue?

BuickRivieraGeorgia wrote:

So, I have gone through a few ICMs, brand new ones from Rockauto gave out in a matter of weeks… I am now back to using the original ICM, which has problems when car heats up to running temps…
Does anyone have a solution to this? Is there anyone selling a supercharged ICM, which is reliable?
How did you guys solve this issue?

There is no simple solution, although the ICM is a really simple device. You may have something else wrong, like a wire to the ICM broken inside the insulation, that is driving your "failures."

That said -- If you tell me what you installed (*which* ICM you bought from RA) and how you installed it then I can probably tell you what to do to get things right.

Start there and in the meantime check for a wire broken inside the insulation at the ICM connector.

Albertj

albertj wrote:

BuickRivieraGeorgia wrote:

So, I have gone through a few ICMs, brand new ones from Rockauto gave out in a matter of weeks… I am now back to using the original ICM, which has problems when car heats up to running temps…
Does anyone have a solution to this? Is there anyone selling a supercharged ICM, which is reliable?
How did you guys solve this issue?

There is no simple  solution, although the ICM is a really simple device. You may have something else wrong, like a wire to the ICM broken inside the insulation, that is driving your "failures."

That said -- If you tell me what you installed (*which* ICM you bought from RA) and how you installed it then I can probably tell you what to do to get things right.

Start there and in the meantime check for a wire broken inside the insulation at the ICM connector.

Albertj

Thanks for the reply, I’ll try to look for the wire and get back to you…

So, I’ve tested the wires, all of them seem to be in good shape.
The car loses power approximately when it hits running temperature. Then if you shut it off and wait till the engine cools off - it runs well again…
I’ve had a situation where I had to push it and let it run for another 40 minutes in traffic when it had acceleration issue… After I pulled over - the car wouldn’t start, but it was weird because it wouldn’t crank at all - it had no reaction to me turning the key… So, this is why I believe it’s the icm

Also, I’ve changed the cam&crank sensors last summer.. replaced plugs recently… tested/switched coils…
What am I missing?
As far as I understand, crank sensor won’t start when heated-which only happened once in my case - the problem is loss of power, like it can’t drive uphill…

Could a camshaft sensor cause this,
I do have a few codes … I will post them soon

You need a scanner that lets you capture data from all the different sensors so that you can take a log of what the car's doing.  Right now we're just guessing at where to fire the parts cannon at a dark landscape. With a log we'd be able to tell if a sensor is flaking out (for instance a temp sensor stuck on full hot, which will make the PCM fire on every other cylinder to keep block temps down while you limp - does this when you're low on coolant too - cool feature ha ha)

In my personal experience low-priced crank sensors (standard t-series) only last 18-24 months in normal driving. I don't like pulling the flywheel so I installed a Delphi and have not talked to the crank sensor since.

One thing I forgot to ask, is the check engine light on?  Whether it is or not, pull the codes and see what is stored/pending. List them here.

The only thing that can cause a no crank condition with loss of power is the ICM, as far as I understand… the crank sensor still cranks the engine even if it’s bad… so does the cam sensor, doesn’t it?
It can only be the ICM, starter or battery connections as far as I know, but the other two dont explain the loss of power. Also this happens when hot, so it all suggests it’s ICM…


I do have a scanner… If you can help me, I can provide logs… I just don’t have enough experience to diagnose/read them…

BuickRivieraGeorgia wrote:

The only thing that can cause a no crank condition with loss of power is the ICM, as far as I understand… the crank sensor still cranks the engine even if it’s bad… so does the cam sensor, doesn’t it?
It can only be the ICM, starter or battery connections as far as I know, but the other two dont explain the loss of power. Also this happens when hot, so it all suggests it’s ICM…


I do have a scanner… If you can help me, I can provide logs…  I just don’t have enough experience to diagnose/read them…

"The crank sensor still cranks the engine even if it's bad..."

No, it does not consistently crank the engine if bad - depends on the degree of failure - from personal experience. Here are some details.

On this car (the Gen. 8 Riv) if the crank sensor does not send signals during POST (power on self test, the time when you turn the key and wait for the car to start) the Riv will crank but it will not start because the PCM will not enable the ignition. (Conversely, if everything is 100% right it will start in 120 degrees of crank rotation...)

It happens when hot because... the crank sensor is a Hall Effect sensor that gets pulses from notched cylinders on the inboard side of the flywheel. The current is very small. The failure mode is that the electrical connections inside the sensor eventually crack and you'll get various kinds of failures. One failure mode is the crank sensor will send signals when cold and when it heats up the breaks in the internal connections expand enough to go open-circuit, and quit sending signals. When that happens the PCM shuts down the engine, hard - no crank means (to the PCM) that the unstoppable force of the Riv has met some sort of immovable object that is stopping the engine from turning and so for life-safety it shuts down the system immediately (it does not check for, say, airbag deployment, and in this case it does not calculate crank position from the cam sensor signals). When the car cools a bit it may well restart like nothing happened. Another failure mode is that the the crank sensor has failed bad enough that it won't send signals at start-up, so it won't start at all. Yet another is that it will let you drive somewhere then you park it and while parked the sensor connections let go due to radiant heat from the engine, "heat soak" of the sensor - the sensor is on the cast iron block - and you can't restart it while warm because the PCM will fail the POST. After a while it may restart.

By the way - a failure that acts similar (crank but won't start) is the ignition switch (NOT the key cylinder, there is a rotary switch that attaches to the cylinder with at least a dozen wires to it - that thing), when that switch goes the car either won't start or will cut off while running as if you turned off the ignition switch for some reason.

I wonder if you kept those ICMs, as they may well be good. Also, when you install the ICM you need to clean the ground plate on the ICM mount. Wire wheel or emery cloth it shiny - then coat it with either conductive grease (NoAlOx) or dielectric grease (tune-up grease, typically dimethylpolysiloxane). One failure you see a lot on the ICM is when a hobbyist (car owner) replaces it and does not use any corrosion inhibitor on that ground plate. In the engine compartment environment it does not take all that long for an oxide layer to build up on it and mess with the ICM function if you don't.. . you don't' need to slather on a load of grease but you do need to wipe the entire plate with it or else it will likely fail after several months or so.

As for the logs, What you'll see on your scanner log is a lack of signal or an erratic signal from the crank sensor, if you were indeed logging that parameter.

If your battery connections are bad your starter won't spin all that well -- don't need a scanner log to discern a slow crank.

Cam sensor is a relatively easy replacement and they don't fail all that much - matter of fact the last "cam sensor failure" I saw was on a friend's car, the magnet for some reason had come unglued and shifted on the cam gear so that the sensor could not "see" it. Conversely, the crank sensors die from heat, when you replace them you Must Not Cheap Out. If you're asking me, get a Delphi.

First of all, really appreciate the detailed response! Am learning a lot from you…
The reason I don’t think it’s the crank/cam sensor is because I’ve had those fail and it really feels different… I might be wrong, but the engine never just dies like it does on crank sensor heating up. Also, it never has problems starting if it cranks. The problem is, it sometimes doesn’t wanna crank at all and that’s what’s so confusing…

About those ICMs, I can be sure they’re bad because the car wouldn’t start with them. The last two ICMs I changed worked great for 2-3 weeks, then car wouldn’t start, it cranked but didn’t start. Then I installed the original ICM, which I was suspecting to be the culprit in this heat trouble, and the car started and ran great when cold. It only had trouble in the summer, in traffics.
I did keep them btw and can test it again, but I doubt they will start the car…

When I would install them, it came with the grease you’re supposed to put on it and I always used it… I did also clean the oxidation with a wire brush, so that’s not an issue

I drove the car yesterday on a highway, it drove well if the water temps were cool (80celsius). but as soon as I would slow down in the city traffic it would start to lose power and start to vibrate/jerk - but the engine never died…
So as far as wind is cooling the engine, the sensors or the icm stays cool enough for it to accelerate and run well…
Is this consistent with crank/cam sensor failure?

BuickRivieraGeorgia wrote:

First of all, really appreciate the detailed response! Am learning a lot from you…
The reason I don’t think it’s the crank/cam sensor is because I’ve had those fail and it really feels different… I might be wrong, but the engine never just dies like it does on crank sensor heating up. Also, it never has problems starting if it cranks. The problem is, it sometimes doesn’t wanna crank at all and that’s what’s so confusing…

About those ICMs, I can be sure they’re bad because the car wouldn’t start with them. The last two ICMs I changed worked great for 2-3 weeks, then car wouldn’t start, it cranked but didn’t start. Then I installed the original ICM, which I was suspecting to be the culprit in this heat trouble, and the car started and ran great when cold. It only had trouble in the summer, in traffics.
I did keep them btw and can test it again, but I doubt they will start the car…

When I would install them, it came with the grease you’re supposed to put on it and I always used it… I did also clean the oxidation with a wire brush, so that’s not an issue

I drove the car yesterday on a highway, it drove well if the water temps were cool (80 celsius). but as soon as I would slow down in the city traffic it would start to lose power and start to vibrate/jerk - but the engine never died…
So as far as wind is cooling the engine, the sensors or the icm stays cool enough for it to accelerate and run well…
Is this consistent with crank/cam sensor failure?

Actually, the scenario you describe may be crank sensor issue - and at the same time I see your point about the ICM.

My hunch, thinking back on my experiences, is they both may be flaky. Engineering is such that components can be designed to operate properly for a certain number of hours (electronics) or miles (rotating/drivetrain), at least at minimum.

When my ICM failed I put one on that I got from Carquest. It was not long after that my local GM dealer replaced it, by necessity, with a Delphi. What I learned then was that the aftermarket ICMs varied wildly in quality.

The ICMs are the same across the 3800 line, the difference between supercharged and normal is determined by timing coming from the PCM. The coils differ between supercharged and NA ignitions, but I don't know how you get supercharged coils new; matter of fact, I had excellent results from getting junkyard units.

My next 'move' would be to get an install a good junkyard ICM and a good new crank sensor. If you click on the part number on the GM ICM in Rockauto.com, you will find a list of cars that use the same ICM. With that list, visit or call junkyards and get three ICMs out of the newest cars you can find in the yard that are on that list. Then I would replace the crank sensor and put one of the used ICMs on. If I got the same problems, I'd do data logging during a drive and see what went wrong. I suspect most likely I'd be putting on another of the JY ICMs unless the data log told me to do something else.

If the problem is the ICM, at least one of those three will work.

If the problem is the crank sensor, you'll be done after step one. And JY ICMs are cheap - our local pick and pull sells them as miscellaneous electronic parts for less than $20.00 - the SC coils, if you can find them, are $15 each. The pick and pull may sell you SC coils (if they have them) and an ICM as a package for $60 or so. Make a deal...

Keep us posted as to what you do and we'll keep working on this until we solve it.

I did order another ICM and I do have a crank sensor laying around that I can install as well… I do wanna do it one at a time though, to be sure to know what was causing the power loss… I will check data logs too, but I don’t think I have crank sensor output… mine’s obd1 because it’s 1995
Anyhow, thanks for all the help, much appreciated!
I’ll post if ICM fixes it

https://obdadvisor.com/codes/wp-content/uploads/2023/07/gm-obd1-codes-list.pdf

Hmmm, caught me there -- looks like there  isn't an OBDI code for crank sensor; looks like you'll need to use an oscilloscope or a multimeter with datacapture  and probe the leads (yuck).  Here's a video posted by a fellow not too far from me (Paul "Scanner" Danner,  South Main Auto) who has a clue about getting that data with a voltmeter:

https://www.youtube.com/watch?v=yp_kK6U8a64

Don't cheap out on those parts...

Albertj


I don't know the history of your 'crank sensor laying around' but over the course of 400,000+ miles I had three.  The one on the car which failed at a hundred something thousand miles, then a Standard that failed in about 2 years flat (about 45000 miles of use) and then a Delphi that, by all appearances, you could not kill with a sledgehammer. As much that pulling the crank pulley feels to me like doing brain surgery with a breaker bar (to avoid ripping the damping rubber) really, I'd just replace the thing with a new Delphi and go from there.

Here is another video, same topic, more applicable to GM:

https://www.youtube.com/watch?v=RvuzZJqQDf4