code 51

hi guys purchased a 1991 blazer 4x4 remanfactured 4.3 . check engine light is flickering constantly . I did the a/b jumper i get a code 12 and a code 51 code 12 is in diagnostics correct ?. code 51 is damaged or faulty connection faulty prom ecm/pcm. where would i start to find eliminate one or the other. thanks in advance.

Your ecm is under the glove box... Check all connections and check the harness at the firewall. If all is ok there it's most likely a fault ecm prom or memcal

ok thanks for the fast reply i unplugged and replugged in all the plugs under dask on both those boxes,after pulling the negative and both ecm fuses. plugged plugs back in and then fuses then neg to bat. i still have a fast blinking check engine light and a code 51 . the vehicle does start and run. rough idle. Now i dont wanna drive this till i see whats causing the code and the blinking light. where to next??????????????im still searching through the search havent found what im looking for...yet. thanks again in advance , shon

ok thanks for the fast reply i unplugged and replugged in all the plugs under dask on both those boxes,after pulling the negative and both ecm fuses. plugged plugs back in and then fuses then neg to bat. i still have a fast blinking check engine light and a code 51 . the vehicle does start and run. rough idle. Now i dont wanna drive this till i see whats causing the code and the blinking light. where to next??????????????im still searching through the search havent found what im looking for...yet. thanks again in advance , shon


ok i have the hole ecm box and prom and all on my pc desk waiting for answers. is there a way to check the prom and mem cal? i havent priced yet but guessing get my check book out eh?.

If you are comfortable working on electronics, I suggest taking the circuit boards out of the box and checking for cold solder joints on all of the connector pins.
A COLD solder joint can look like a circular crack around the pin. To fix, heat it up with soldering iron and add a SMALL amount of solder. I fixed one like this several years ago and it was a permanent fix.
If you don't know what your looking for and think this ECM is dead, then you might try reheating all the pins on the board and then hook it up to see if it works. It might be a long shot, but it is free except for your time.

ok i looked for cold cracks and didnt see any. not that there isnt any lol. i pulled the 2 chips a seated them again and i am going to put it back in. i have no idea whats bad but got a blinking engine light and code 51.if i go get it scanned will scanner gimmie a better break down? and i take it i cant check these? feels like im building my pc again. too bad im carpenter.

ok all is done and back together resetthe ecm and now its a stuck on engine light no flicker(no clue what changed it) still code 51 runs fine. what should i do?

should i swap with a known good ecm and prom ? or does the code 51 ever mean something besides what its meant for? just bought this blazer and need help asap.

ok replaced the computer the prom and the other chip in the computer. still code 51 still fast flickering check engine light. wheres the memcal is that the plastic box mounted to the side of the computer box. any help would be greatly appreciated as i dont want end up stranded some where trying to figure it out.

the memcal IS the chip

ok thought that was the prom so 2 chips one prom one memcal? if so then have replaced all. now what i do just drive it ? also wheres the speedo sensor that thing hops all over when it chooses to work at all. no cable so im lost and my clymer shows nothing ...