SOLVED! I killed the PCM.

[escapepilot]

I've been running a Superchips Flashpaq to reprogram the tire size and axle ratio and running an economy tune for now. Yesterday, I needed to go pick up a tractor and haul it home. I went to switch the tune to a tow tune and halfway through reprogramming, it lost communication to the databus. Followed all on screen directions and tried it again. Nope. Tried a third time...would even connect. Tried my OBD reader...wouldn't connect either. Trying to start it doesn't even get a click on the starter. Everything I've found online says the PCM will have to be reflashed and maybe replaced. Anyone experience anything similar? Could a dealer reflash just the PCM w/o the TB there.

Guess I'll be giving Superchips a call tomorrow since tech support wasn't open on Saturday.

[gotspeed1]

I'm certainly not the foremost expert on this and have been away for quite awhile, but, from what I remember, it probably needs a re-flash. I sure the dealer could do it without the truck being there (same theory as sending it out for programming), or you could just order a new one from a company (PCM4less?) that is programmed to your specifications. A guy I used to work with fried his PCM and got a fancy $800 bill from the dealer for a new one, so keep that in mind.

[escapepilot]

Superships thinks it happened to a low battery voltage. They think a good charge followed by reconnecting the programmer should take care of the problem. Seems optimistic, but since charging the battery is free... I'll report back later.

[Ole Blue]

Good luck.


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[escapepilot]

So far no luck, but I have a lead now. So far, the Superchips tech thinks it's not get 12.8 volts which won't allow the programmer to run; however, even a new battery didn't solve that issue. I spoke to a GM tech tonight and he feels it could be an issue with the ignition switch. Since they have know issues, are relatively easy to change, and I may be able to get a donor for nothing...definitely going to try that route next.

Will keep you guys posted.

[KielTb]

I recently had a very similar issue. Tried hooking hptuners to do a flash and tune. Truck kept resetting the pcm mid read and after about 4 attempts started the flash and randomly died about 40% through it. 2 used pcms later the dealer ordered in a preflashed pcm and threw the truck back at me. Now the entire stereo doesnt work(aftermarket pioneer head unit) the dealership couldnt communicate with the pcm or bcm. My tuner thought a data line was broken or frayed at the firewall between the pcm and obd2 connector. I havent had the gonads to risk trying to tune it again because the dealership couldnt tell me what they did to troubleshoot or fix the issue other than put a preflashed pcm in it. Going to hopefully go to a u pull it yard this week to get what i need for a bench harness to attempt a flash safely outside my tb's electrical nightmare....

[Jimw]

Check the pcm fuse in the underhood fuse box?

[escapepilot]

Verified that all fuses are good. Haven't had a chance to check the ignition switch yet.

[escapepilot]

ITS ALIVE! Finally got it to communicate and recover the stock program. Talked to the tech again and he suggested pulling the fuse on On Star since it could slow down the data bus. I also pulled the radio and amp fuses since I have an aftermarket head unit with adapter harness (thanks, Kyle. Your post made me think of the radio.)

**edit corrected typo - HEAD unit.

[KielTb]

Very much welcome escapepilot. I may want to look into the onstar slowing down the data bus. My tuner was telling me a whole list of things that could be draining my voltage causing my pcm to reset during reading. Havent been brave enough to try in vehicle read yet. Might make it to the local yard today for the blue connector for a bench harness :pray: