ICM keeps dieing?
I'm going to attempt to help you. Hook your meter directly across the battery and tell me the voltage it reads. Engine off, key off.
The ICM has four wires going to it. Put the red lead from your meter on the positive battery terminal and the black lead on ICM terminal A. You can unclip the back of the connector, pull out the rubber seal and get a small wire in the connector with it still plugged into the ICM. Do not unplug the connector from the ICM. With the key on engine off what's the voltage reading?
With the black wire of the meter on the negative battery terminal and the red lead on terminal C of the ICM what's the voltage? Again, key on engine off.
You can't really get any good information on terminal B or D of the ICM with your meter so don't waste time with it.
Are you running the stock coil?
Post the information and I'll get back to you.
Al 95 Z28
The ICM has four wires going to it. Put the red lead from your meter on the positive battery terminal and the black lead on ICM terminal A. You can unclip the back of the connector, pull out the rubber seal and get a small wire in the connector with it still plugged into the ICM. Do not unplug the connector from the ICM. With the key on engine off what's the voltage reading?
With the black wire of the meter on the negative battery terminal and the red lead on terminal C of the ICM what's the voltage? Again, key on engine off.
You can't really get any good information on terminal B or D of the ICM with your meter so don't waste time with it.
Are you running the stock coil?
Post the information and I'll get back to you.
Al 95 Z28
17.86v
The ICM has four wires going to it. Put the red lead from your meter on the positive battery terminal and the black lead on ICM terminal A. You can unclip the back of the connector, pull out the rubber seal and get a small wire in the connector with it still plugged into the ICM. Do not unplug the connector from the ICM. With the key on engine off what's the voltage reading? =
16.52v
With the black wire of the meter on the negative battery terminal and the red lead on terminal C of the ICM what's the voltage? Again, key on engine off. =
0.02v
You can't really get any good information on terminal B or D of the ICM with your meter so don't waste time with it.
Are you running the stock coil?
Yes
A battery lead acid car battery is a nominal 12v. You could see small variations to either side of that. The altenator would only show @ 13.8-14.4 volts if the vehicle was running and that would be the highest reading you could/should EVER get.
Unhook all the cables etc rom the battery and test across the terminals and see what you have, if its still high there is an issue within the battery!
Unhook all the cables etc rom the battery and test across the terminals and see what you have, if its still high there is an issue within the battery!
The test with the red meter lead on the positive battery post and the black meter lead on ICM terminal A is wrong. Check it again, key on, engine off. If you get the same reading, check positive of the battery to the B terminal of the coil.
Al 95 Z28
Al 95 Z28
TECH Veteran
Joined: Dec 2008
Posts: 4,147
Likes: 62
From: Little Rock, AR
Al 95 Z28 went 12.31 yesterday. Now if I could only learn to tune it
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
Gas Monkey Built a 6-Wheel Ferrari Testarossa With a Corvette LT4 Engine
Verdad Gallardo
7 Most Reliable High-Performance Engines GM Has Ever Built
Verdad Gallardo
Amazing '71 Camaro Restomod Is Modern Muscle Car Under the Skin
Verdad Gallardo
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo tell you what guys. ignore all my previous results.
you guys are the best. i went ahead and bout a new multimeter.
i got new results.
Opti harness terminlas A to D with key on ignition. car off.
A - 5.03v
B - 5.03v
C - 11.68V
D - 0.03v
Battery with or without cables read 12V.
im going to test the the ICM like Big Al Stated.
you guys are the best. i went ahead and bout a new multimeter.
i got new results.
Opti harness terminlas A to D with key on ignition. car off.
A - 5.03v
B - 5.03v
C - 11.68V
D - 0.03v
Battery with or without cables read 12V.
im going to test the the ICM like Big Al Stated.
I restested with new multimeter.
Disconnected the ICM connector. Leave coil connected.
Turn key to ON.
Check for dc voltage with a digital meter at harness terminal "A" to ground and and also "D" to ground.
If you have good voltage, switch the meter to ac scale and connect test leads to terminal "B" and to ground. Observe meter while cranking the engine. You should see beeived 1-4 volts while cranking.
tween 1 and 4 volts ac (those are the pulses that trigger the coil to fire).
Disconnected the ICM connector. Leave coil connected.
Turn key to ON.
Check for dc voltage with a digital meter at harness terminal "A" to ground and and also "D" to ground.
i received 11.68 volts on both
If you have good voltage, switch the meter to ac scale and connect test leads to terminal "B" and to ground. Observe meter while cranking the engine. You should see beeived 1-4 volts while cranking.
tween 1 and 4 volts ac (those are the pulses that trigger the coil to fire).
I got around 1-4 volts AC 
Now that you have the correct results.......
Are you using Delco parts? That would be my only guess, plenty of thermal grease on back?
The only other thing that comes to mind is on the ICM harness (because that is where the problem shows) did you verify those numbers to the harness ground? Sometimes that ground becomes compromised and you will see correct numbers to chasis ground and not in the harness.
In testing the ICM make them run the test 5 times consecutively. If there is a weak spot in it, it should show by the 4th test.
I had an oddity and couldnt find it and assumed it was ICM related because it would only do it after the car got hot, not a closed loop problem just a thermal situation. EVERYTHING pointed to ICM. I checked everything and kept double checking and could never get it to do anything out of the ordinary. I would get an occasional SES low res code so I then turned my attention to the opti. Sure enough when it got hot, it had failure just as an ICM would have. It was a bitch to find but I waited til it did it (in my driveway) and then did all the tests and noticed the AC pulse wasnt toggling. I replaced the opti and it is all better with no recurrent codes or signs. Just another thought for you.
I also HAVE NEVER seen an LT1 that didnt need work on the grounds located behind the coil to the head. The ring terminal become weak and break, or in most cases crack.
Are you using Delco parts? That would be my only guess, plenty of thermal grease on back?
The only other thing that comes to mind is on the ICM harness (because that is where the problem shows) did you verify those numbers to the harness ground? Sometimes that ground becomes compromised and you will see correct numbers to chasis ground and not in the harness.
In testing the ICM make them run the test 5 times consecutively. If there is a weak spot in it, it should show by the 4th test.
I had an oddity and couldnt find it and assumed it was ICM related because it would only do it after the car got hot, not a closed loop problem just a thermal situation. EVERYTHING pointed to ICM. I checked everything and kept double checking and could never get it to do anything out of the ordinary. I would get an occasional SES low res code so I then turned my attention to the opti. Sure enough when it got hot, it had failure just as an ICM would have. It was a bitch to find but I waited til it did it (in my driveway) and then did all the tests and noticed the AC pulse wasnt toggling. I replaced the opti and it is all better with no recurrent codes or signs. Just another thought for you.
I also HAVE NEVER seen an LT1 that didnt need work on the grounds located behind the coil to the head. The ring terminal become weak and break, or in most cases crack.
Now that you have the correct results.......
Are you using Delco parts? That would be my only guess, plenty of thermal grease on back?
The only other thing that comes to mind is on the ICM harness (because that is where the problem shows) did you verify those numbers to the harness ground? Sometimes that ground becomes compromised and you will see correct numbers to chasis ground and not in the harness.
In testing the ICM make them run the test 5 times consecutively. If there is a weak spot in it, it should show by the 4th test.
I had an oddity and couldnt find it and assumed it was ICM related because it would only do it after the car got hot, not a closed loop problem just a thermal situation. EVERYTHING pointed to ICM. I checked everything and kept double checking and could never get it to do anything out of the ordinary. I would get an occasional SES low res code so I then turned my attention to the opti. Sure enough when it got hot, it had failure just as an ICM would have. It was a bitch to find but I waited til it did it (in my driveway) and then did all the tests and noticed the AC pulse wasnt toggling. I replaced the opti and it is all better with no recurrent codes or signs. Just another thought for you.
I also HAVE NEVER seen an LT1 that didnt need work on the grounds located behind the coil to the head. The ring terminal become weak and break, or in most cases crack.
Are you using Delco parts? That would be my only guess, plenty of thermal grease on back?
The only other thing that comes to mind is on the ICM harness (because that is where the problem shows) did you verify those numbers to the harness ground? Sometimes that ground becomes compromised and you will see correct numbers to chasis ground and not in the harness.
In testing the ICM make them run the test 5 times consecutively. If there is a weak spot in it, it should show by the 4th test.
I had an oddity and couldnt find it and assumed it was ICM related because it would only do it after the car got hot, not a closed loop problem just a thermal situation. EVERYTHING pointed to ICM. I checked everything and kept double checking and could never get it to do anything out of the ordinary. I would get an occasional SES low res code so I then turned my attention to the opti. Sure enough when it got hot, it had failure just as an ICM would have. It was a bitch to find but I waited til it did it (in my driveway) and then did all the tests and noticed the AC pulse wasnt toggling. I replaced the opti and it is all better with no recurrent codes or signs. Just another thought for you.
I also HAVE NEVER seen an LT1 that didnt need work on the grounds located behind the coil to the head. The ring terminal become weak and break, or in most cases crack.
Both were not ACDelco parts. I do get recurrent codes. which lead me to change it to a remanufactured. meh i know bad idea. i will replace the ground wires going to coil. i was also thinking of placing the ICM in another location. as long as the ICM wire reaches and the grounds reach. relocation should be fine, right? i will put it by the fender side by the headers or the engine bay drivers side. just to have it cool off quicker.
.i will end up buying an ACDelco part after i see better results without it dieing.
might as well get it running without being scared of what can happen next. il keep yall update.
I had a similar problem years ago using an ICM from Advance Auto. My car would run and drive until it got up to temp and then the car would stall. It would not start back up until I replaced the ICM with a new one. I replaced the Advanced one 3 times and still had the same result so they ended up just giving me my money back and I went with a used AC delco one I bought from camaroz28.com and it has not died since. It has been working for over 7 years without an issue. I still to this day though carry a spare ICm in the hatch just in case as I chased this problem for nearly 6 months. I would replace yours with an AC delco unit.
I got mine from Oreilly's Auto Parts. Im going to go over there and let them know its been more then 3 times ive replaced the part which has lifetime warranty.
For the opti they told me they would replace it for the last time and for next time they would give me my money back. so maybe they will do that for the ICM, lol. then i get money back and get the ACDelco ICM. lol
For the opti they told me they would replace it for the last time and for next time they would give me my money back. so maybe they will do that for the ICM, lol. then i get money back and get the ACDelco ICM. lol
I did notice that when i got the new ICM. It came with come dielectric paste. installed the ICM and got the same results of the car stalling. so maybe dielectric paste not working good enough.
can that cause me issues due to the fact that the dielectric paste is not doing its job so well?
can that cause me issues due to the fact that the dielectric paste is not doing its job so well?
Last edited by davidc212k; Nov 17, 2011 at 11:47 AM.
so todayi spliced new ground wires that are by the ICM the yellow and the black and the ground. out of the sudden after not turning the car on for 1 week. the rpm idles at 1350 and sometimes drops. what can cause this. bad opti, ICM, IAC or TPS?
I also noticed that when car stalls or dies, i loose spark. even after letting it rest for 30 minutes. still no spark. i tested with an extra coil and still no go.
all thats left to test is ICM and Opti. Has anyone ever bought the chandler optispark? are they any good? as for the ICM i will go acdelco.