Computer Harness Problem
Thread Starter
Staging Lane
Joined: Jan 2007
Posts: 59
Likes: 0
Computer Harness Problem 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!
Anyone know what my problem(s) could be?
Thanks!
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.
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.
Joined: Nov 2001
Posts: 1,707
Likes: 33
From: Anderson, Indiana
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.
__________________
91 Z28 LS2 408CI, LS9 Supercharger, LPE GT7 cam, Yank3000, 3450 raceweight.
Latest numbers: 9.71 ET, 141.42 MPH, 1.40 60' , 610 RWHP Mustang Dyno
www.speartech.com
91 Z28 LS2 408CI, LS9 Supercharger, LPE GT7 cam, Yank3000, 3450 raceweight.
Latest numbers: 9.71 ET, 141.42 MPH, 1.40 60' , 610 RWHP Mustang Dyno
www.speartech.com
Thread Starter
Staging Lane
Joined: Jan 2007
Posts: 59
Likes: 0
Originally Posted by Speartech
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.
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
Joined: Nov 2001
Posts: 1,707
Likes: 33
From: Anderson, Indiana
The fan relays ARE grounded by the computer, so that part sounds like it may be wired correctly.
__________________
91 Z28 LS2 408CI, LS9 Supercharger, LPE GT7 cam, Yank3000, 3450 raceweight.
Latest numbers: 9.71 ET, 141.42 MPH, 1.40 60' , 610 RWHP Mustang Dyno
www.speartech.com
91 Z28 LS2 408CI, LS9 Supercharger, LPE GT7 cam, Yank3000, 3450 raceweight.
Latest numbers: 9.71 ET, 141.42 MPH, 1.40 60' , 610 RWHP Mustang Dyno
www.speartech.com
