Hey Forum. Im having a hard time getting to the bottom of this random shut down. Car starts strong when cold. When it warms up however, it will randomly die without any warning or check engine light. No sputtering or loss of power,
just shuts down as if you turned off the key. It will not start after it dies, it will just crank and crank but wont turn over until a few hours has passed , then does the same thing. Power will stay on. Installed a new battery and actually brought it to a shop but they couldn't figure it out. Anyoje had this issue before??

 

Welcome to the forums. Sounds like a heat related issue and yes they will drive you nuts. I did have that problem once, when I installed a 2000 LQ4 engine and transmission into a 84 GMC 3/4 ton 4wd. It was a salvage operation with the the complete wiring harness and PCM included. It had many wires I did't need and removed, after several running hours it developed that same issue. I traced it down to the main fuse box, fuses were fine the problem was a loose wire on the back side of the fuses, where the wires plugged into the fuses. There was a wire plugged into the ignition fuse was loose, worked fine cold but when warmed up lost contact. Cleaned and tightened the connection and had no problems sense. Or you could have a Body control module BCM issue, Any error codes? Ignition problem only? Have you had any service done or played with any wiring recently?

 

Welcome to the forum. Another possibility is when the ECM switches from open loop to closed loop when the engine is warm enough, something isn't functioning correctly. I don't know enough about how that function works but it's a place to check. You might have to take it to a dealer that has the capability to do a full scan.

 

Reading up on the C-5 ignition problems there is the ICM ingition control module Which has a Power transistor, Capacitor, Heat sink and the wiring harness, could be an issue. And there is also the ignition lock cylinder maybe needs replaced. THat should keep your mechanic scratching his head.