1991 gmc sierra 3500 7.4l engine turns over won't start

Asked by tryn2Bamech Jun 15, 2017 at 10:17 AM about the 1991 GMC Sierra 3500 2 Dr C3500 SLE Extended Cab LB

Question type: Maintenance & Repair

A re-occurring issue with this truck. I'm sure if I change the ICM again it will start right up. just looking for additional information. The ones I replace always test good at the local Autozone. Maybe somebody else has had this issue.  

4 Answers


On those rigs that seem to keep having thermal failures I made up a wiring harness and relocated the module to the fender or the front bulkhead away from any heat source. HTH

Thanks tennisshoes, I might try that. Are the connectors carried at parts stores or is this a wrecking yard item.


I just spliced into the existing harness with the right amount of wiring to put it anywhere I wanted soldered ans heat shrinked the connections and then put wire loom shielding on the manufactured harness.

I decided to go ahead with another ICM. It took a minute since I had modified the distributor cap attaching screws. Have to use nuts and bolts. Anyway as I thought it started right up. I will be tracking this issue. I would really like to know what's the real cause of the repeated failures. Thanks much for your help. If I decide to go your route I will certainly let you know. Right now I've got to replace my tailgate hinges. Hope they work as I ordered them on-line. Thanks again.

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