'97 Z28, A4, OBDI PCM installed. Started to load a tune using TunerCat when I got a "Battery Voltage Out of Range" error message and the upload was aborted. I hadn't noticed how low the battery had gotten. I know, bonehead mistake.

Now I can't reestablish communicating with the PCM. DID I give the PCM a lobotomy? Any suggestions? Will a simple PCM reset do the trick? Thanks.

 

Normally, when the upload was aborted in the middle, you have just had sex. Not the good kind, the kind that hurts your bunghole.
Our PCMs do not have a recovery mode like the new ones have.
You could try a reset, but you have most likely made a brick. Tuners could rewrite the tune, or you could buy a used PCM for around $50 and try again.

 

I'm getting ready to find out if a reset will do it. I was 20-30 seconds into the upload.

 

You bricked it. It can be repaired, the FLASH chips will need to be removed from the board and manually reprogrammed. You can try pulling the PCM IGN fuse or the battery cable to reset it, but unless you are really, really lucky and it hadn't actually erased your FLASH chips.

Since you almost certainly fried it, you should probably just have the PCM socketed so they chips can be removed easily in the future in case it happens again and get an extra set of FLASH chips to swap in. That way you can just send the chips off to be reprogrammed if you don't want to buy a programmer to do it yourself.

 

Lucked out. Now I have to run a data log and see why its running so rich and bogging really bad when I advance the throttle. Think I'll go buy a couple of lottery tickets too.

 

Congrats, you should buy the tickets. The normal sequence is:
Initialization and synchronization
Erase
Write
Clean up

It sounds like you ended during the first sequence, you are lucky indeed. Enjoy.

 

Thanks. LOL

 

Voltage is checked before programming begins. The PCM can only program if the voltage is within a certain window - too low or too high, it won't work. I have some benchtop 13.8V power supplies that won't work with PCMs because they register as "too high"... but drop the voltage with a couple of diodes, and they'll work fine.

You won't brick the PCM if this happens (as you found), but you very well might lock it up. It would just need a reboot - pull the PCM fuses and reset it, and then plug the fuses back in. Should be good to go.

 

It is OK. I was dealing with a low voltage situation where it must have been just above the low end of the voltage operating parameters when I started the upload.