i have an 87 trans am 5.7, i read the prom with a moats auto prom. from the address 0 to 4000 all that I have is FF. the prom is ABWT. from that point on there is code. i just bought this car and it has been sitting for about 10 years. i have used the auto prom on several GM chips and have never had this issue. Can a prom partially erase itself, from sitting for several years. any help on this would be greatly appreciated

 

you did read it as a 27C128 correct? the BIN itself only goes to 3FFF....

i have one on my laptop and it looks fairly normal...

 

let me go a little farther on this problem. i just bought this car. it has been sitting for about 10 years. the person i bought it from replaced the fuel pump, spark plugs, wires, cap and rotor. when the transproter put it on the truck it died out after it ran for about 10 minutes. it started up when the car got delivered to me. i put a scan tool on it and found the coolant temp reading 230 degrees and it was cold running for about 2 minutes. i unpluged the coolant temp sensor and the scan tool should have read -40. it was reading 130 degrees. i check for the 5volt signal and it was reading 3.5 volts. i did the usual voltage drop and ohmed out the wiring and it checked out ok. i ordered a reman PCM. also this car has a bad alternator, it stops and starts chargeing intermittantly. i pulled the prom to download the bin to a file so i could change the fan turn on temp, i'm puting in a 180 degree t-stat. i have a moates auto prom and tuner pro software. when i downloaded the prom and looked at it with tuner pro nothing on the prom matched up to what the numbers should have been. i have up loaded quite a few proms the last 2 years and this has never happened. when i looked at the code in the hex editor it first line had FF in the first and second spot and there was code on the rest of the first line. from the second line to 4000 there was nothing bu FF from 4001 to the end of hack there was code. i uploaded this prom about 10 times and every time it read the same. i have some GM proms sittting around and i'm going to upload one of them tonight and see if it reads the same as the original prom i read. either this prom is bad or there is something wrong with the auto prom makeing it read incorrectly. the car car runs half decent. if the prom is corupted it should run pertty bad.a bad alternator or jumping a car backward could fry a PCM, could it corrpt a prom? could a prom get corupted from sitting 10 years?

 

Many times in the '7165 MEMCALs GM used a '256 kb PROM and only loaded the top half. Read it as a '256 and only save the buffer from 0x4000 through 0x7FFF. That will give you the 16 KB BIN.

RBob.

 

Thanks, Rbob i did what you said and the prom did read as it should. i'm not very computer or code literate. Thanks again