451stroker

I installed a 1999 LS1 into a 1981 Trans Am using a customized harness from a guy on EBay. My fuel pump relay won't ground when the key is turned to the "run" position. I am also unable to read the codes with my OTC scan tool. Upon connecting the tool with the key in the "run" position, I get the following message: "Unable to establish communications with PCM". I checked for power and ground to the diagnostic plug and they are fine.

Anyone know what my problem(s) could be?

Thanks!

76LQ9TA

iTrader: (1)

Follow the signal wires from the diagnostic port to the pcm. They are C1 pin 58 and 59 on my pcm. It is from a 02 escalade. I don't know if the car pcm's are the same.

C2 pin 9 is the control wire for the fuel pump relay. I would also see that this wire is hooked up correctly to the pcm.

Speartech

iTrader: (14)

The fuel pump relay is always grounded. When you turn the key on the PCM supplies the 12 volt signal for about 2 seconds. You may have something wired up wrong if you are looking for a ground at key on.

451stroker

I can't thank you enough! The harness was wired wrong. I hooked the relay power up to Port 9 and put the ground to the body. The fuel pump works as it should now.

Do the fans also work in the same manner? The guy who modified my harness hooked up the fan relay grounds to the computer also.

Thanks again.

John

Speartech

iTrader: (14)

The fan relays ARE grounded by the computer, so that part sounds like it may be wired correctly.