I have a 94 z28 that I bought 2 years ago, it came with an older hypertech tuner which I used to set the reared setting in order to make the speedometer read correctly. After fixing the speedometer calibration all was fine till a few months later when my water pump went out and took the opti with it. Well I just recently got the car running again after having a shop replace WP and opti. When I got the car back I noticed the speedometer was off again as if the pcm went back to stock rear ended setting. So last night I hook up the tuner to fix the rear ended setting again and the tuner lost connection to the pcm and never finished the download. Now the car seems to be stuck in that download mode and will start for 1 second then die. As soon as I turn the key to on position fans come on and SES light are on as if it’s still attempting to do the download but now tuner says “ no data/ check cable”. Not sure hat to do next...

 

The PCM may be "bricked" now, meaning it can't start up since part of the program is missing. If that is the case, you will either need a replacement "-8051" PCM or send yours to someone who can replace ($?) the memory chip ($5) with a new one, preferably with a socket. You would need that chip programmed before it is placed into the PCM, but with some hardware and knowledge you can do that yourself.The socket would allow you to replace the chip yourself if/when it happens again. Many shops that do programming can also do the chip and socket installation. Some sell the used PCM with a socket installed already.

Replacement exsmple: https://www.ebay.com/p/1994-1995-LT-...d=362587352023