hey guys, i have a 1995 chevy truck, 16197427 $0D ecm. i built a new engine a few years ago and been tuning myself with a moates g1 adapter and ziff socket with an autoprom. no real problems with it. tuning has gone fine. 2 months ago i was getting a random tps error code but the tps was fine. ended up being the computer. i replaced with an acdelco remaned unit. its been ok till last week. check engine light came on and it died a mile from home on my way to work. came up code 51. i pulled ecm and pulled memcal from socket in ecm then put back together and fired up and ran fine. since then it does it almost every morning, and sometimes at lunch. i can always get it running if i fidget with the memcal. it seems related to the cold weather because it does it more in the mornings. its always code 51. ive already replaced the g1 adapter and tried without ziff socket, that didnt help. could it be the ecm is bad? or a bad ecm plug or wire somewhere? what else will cause a code 51? please help. thanks

 

Code 51 is set when the PROM doesn't checksum at key-on. So if there is a bad connection between the PROM and MEMCAL, or MEMCAL to ECM, that will cause a code 51. A bad PROM will also cause a code 51.

If you have another MEMCAL try it. If that doesn't fix it then a good possibility is that a trace or two in the ECM has cracked. Which usually means getting another ECM. Shouldn't have much trouble finding one in a JY.

RBob.

 

Thanks. so a code 51 wont come from a bad ground, or any other bad wire that is in one of the 2 plugs going into the ecm itself? also, you say code 51 is a checksum at key-on error. what would cause the code 51 when this is happening after the engine has started and been runnin for a couple minutes before the code sets? thanks again.