C4 Tech/Performance L98 Corvette and LT1 Corvette Technical Info, Internal Engine, External Engine

LT1 ignition coil driver and ignition control module...same thing?

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Old 07-30-2007, 01:40 AM
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RRT vette
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Default LT1 ignition coil driver and ignition control module...same thing?

When to the local Winn Dixie tonight in the 92 to get a few things. Can back out and it started up and ran for about 3 seconds and died. It will crank but not start. I am getting fuel but not spark at the plugs. I ran through the FSM and seems the ignition coil driver is bad. It has a 4 wire connector. All 4 wires tested good when troubleshooting. I get no spark from the ignition coil.

Says to check the connection at the coil driver (cleaned the connections good) or replace the coil driver. Is the coil driver and ICM the same thing? Looks like it from the online autoparts stores.
Old 07-30-2007, 03:45 AM
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Casethecorvetteman
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Does it have a pic of its location in the service manual?
Old 07-30-2007, 07:32 AM
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Take off the coil and ignition module and get them tested at your auto parts store. I believe Autozone and Advanced Auto will do this for free.
Old 07-30-2007, 08:13 AM
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#1 is pointing to the culprit just above the coil. I am very sure that is the ICM.

Old 07-30-2007, 08:15 AM
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Casethecorvetteman
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Yep, that is indeed the ICM
Old 07-30-2007, 09:14 AM
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Thank you Casey. Now I just need to find a good price on one. Just got back from towing it home. At least now I can work in it.
Old 07-30-2007, 09:49 AM
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Bill Hetzel
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RRT, I just replaced one on my 92. Went thru the pricing BS. I saw prices from $95 to $165(dealership of course). I got one (AC Delco) from Corvette Central for $110 but it took over 2 weeks to get.
Your best bet is to go to your local AC Delco store, they'll probably still have to order it but it should be faster.
CC p/n 274562

From the AC Delco box: ACD# D1971A ( use this at an ACD store)
GM # 10483131

I forgot to add this - The ICM comes with thermal grease to coat the back when installing it, be sure to use it. Also, I had a different problem that your no start. My origional ICM was apparently working alright and the grease on the back was gone, just powdery residue.

Last edited by Bill Hetzel; 07-30-2007 at 09:54 AM.
Old 07-30-2007, 10:31 AM
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Thanks for the tips. I just removed it and am going to have it tested. I found about the same prices online. The heat sink grease is just about non existant on the back of it. If it test good, I will get some grease and reapply.
Old 07-30-2007, 11:10 AM
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Bill Hetzel
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If you have to get a new one, it should come with grease, AC D does.
Thermal grease is a little hard to find, there was a thread on this 3 months ago.
I personnally would subistiture dielectric grease if I couldn't find thermal.
Old 07-30-2007, 04:20 PM
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If you have Advanced Auto Parts store near you they carry the GP sorensen version for $75. It has a long warranty, I think he said 7 years?

I bought one yesterday but it doesn't appear to be my problem. If you can't find one let me know, I was going to just return it but could ship it for cost + shipping.

FWIW I've heard the tests they run on the ICM aren't especially reliable. Coils are quite cheap, it may be worth it to buy both and check the coil before plugging in the ICM. Did you check your resistances across the primary and secondary coils? If you get lucky and it's the coil you can return the more expensive ICM part.
Old 07-30-2007, 04:46 PM
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I took the ICM and two spare used coils to two different Autozones (in different towns) and to a Advanced Auto Parts. None of them could test the ICM for me (didn't have the connection). The first Autozone tested the ignition coils to be good. GM wants $165.00 for a new one.

Wonder if there is a way I can bench test the ICM?

GMpartsdirect.com wants $87.xx for it, but wants $20 shipping. Thats just stupid.
Old 07-30-2007, 04:53 PM
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Advanced Auto Parts tested my ICM and coil for me. Autozone has a lifetime warranty for their ICM at $71.99 for my 96. I think their coils are about $45 and I would not be surprised if there not lifetime too.
Old 07-30-2007, 06:49 PM
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Originally Posted by ericcer
Advanced Auto Parts tested my ICM and coil for me. Autozone has a lifetime warranty for their ICM at $71.99 for my 96. I think their coils are about $45 and I would not be surprised if there not lifetime too.
Hmmm, everyone turned me down when it came to testing the ICM.
Old 07-30-2007, 10:28 PM
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Originally Posted by RRT vette
Hmmm, everyone turned me down when it came to testing the ICM.
Weird. What do you mean "turned you down?" They wouldn't do it, or don't have a tester? Murray's auto around here does it, do you have one nearby?

And you've probably thought of it already, but do you know anyone with a similar year car? It's easy to remove, put yours on another car and see if it runs...post here, there's bound to be someone nearby that will let you do it.
Old 07-30-2007, 10:43 PM
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Originally Posted by ScaryFast
Weird. What do you mean "turned you down?" They wouldn't do it, or don't have a tester? Murray's auto around here does it, do you have one nearby?

And you've probably thought of it already, but do you know anyone with a similar year car? It's easy to remove, put yours on another car and see if it runs...post here, there's bound to be someone nearby that will let you do it.
Didn't turn me down, just didn't have the connector to test it on thier machine. I will have to call some of the local shops around here to see if they can test it. I live about 1 mile from a Chevy dealer....wonder if they can test them? I don't know anyone around here with a LT1 C4. My brother has a salvage 93 that I can get the ICM off of, but the car is 2 hr drive one way from me. It wouldn't pay to drive that far in my 17 mpg truck ($40 in gas).
Old 07-31-2007, 08:10 AM
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If your new ICM doesn't come with it, you can get a tube of thermal grease from Radio Shack for $3.99.
Old 07-31-2007, 09:47 AM
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Might be worth a try to disconnect the MSD adapter and try to run through the original ignition system.

This is really easy to do since the connections are snap togethers.

One less thing to troubleshoot.

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To LT1 ignition coil driver and ignition control module...same thing?

Old 07-31-2007, 01:51 PM
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I cleaned the back of the ICM and it's contact on the head and put some dielectric grease on the back. I disconnected the MSD and still no start.
Old 08-03-2007, 01:36 PM
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You guys want freak'n believe this. I got a used ICM from my dad that was working when he took it off. I couldn't find anyone around here to test mine, so rather than purchase a new one, I decided to use a good spare.

I used dielectric grease on the back and installed it. I had the MSD box disconnected from the battery and tried to start the engine. Same thing...wound crank but not start. I connected the MSD back to the battery and same thing.

Feeling down on my luck, I decided to check the wiring at the ICM and it's good. I had loomed some of the wires when I got the car and started taking the loom off going to the MSD. Found that the ground wire for the MSD was disconnected. The wires apparently were just tied together and electric tape wrapped around it.

I couldn't find a butt connector big enough, so I just twisted the wire back together and turned the key and the engine started. I will have to get a connector for the wire. Might have to go over all the wiring to make sure it's together good.

Wiring problems will drive people crazy...especially me.

Problem solved.....for now. The best thing about it was I didn't spend a dime to fix it.
Old 08-03-2007, 03:06 PM
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That's great news. These situations always make you relieved it was a simple thing, but pissed that something so stupid could happen!


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