Check engine light was on so I pulled the code..it's a 51 which I looked up and is either a bad prom, incorrectly installed prom, or bad ecm (computer). I disconnected the battery..and this code keeps coming back..also the instant mileage and range functions don't work..all the other functions do. Is the chip bad or is it the computer. Any suggestions guru's...thanks..

When my ECM - 1989 - was bad, the instant and average MPG, and range functions didn't work. The car wouldn't idle under 1200 either. I didn't get a code 51, but neither could the ECM be accessed with a scanner.

have you tried pulling the ECU and making sure the chips are set?

A little corrosion could add to the drama, too.

bogus, yes I have pulled the chip out several times it seems like..checked all the little feet and they seem okay. it seems every time I reset the chip it works for awhile then check engine light..pull the code..51..everytime..

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my average mpg works fine..just the instant and the range functions don't. did you get a code 12..when you tried to pull the codes...I was all ways under the impression that if you got a code 12..the computer was working okay..somebody please correct me if I am wrong on that...no other codes other than 51...thanks for your reply..

IIRC, my car wasn't setting any codes.

CAGS and upshift light wouldn't work either.

Took the car to the dealer - the ECM wouldn't communicate with the scanner.

Replacement computer was cheap enough at advanceauto - local, they had one in stock - that I just swapped it out. Was cheaper than the dealer diagnostics charge and it worked fine. Going on two years now.

Put in a new chip and so far so good. No check engine so no codes..have driven the car about 100 miles..so hopefully this takes care of the problem...thanks to all who responded..