Major Electrical Problems
Thread Starter
Launching!
Joined: Mar 2012
Posts: 299
Likes: 21
From: Phoenix, AZ
Major Electrical Problems And to add to my recent saga of issues...
Heres the story:
The Chevelle has been running great until Thursday night. I went to start it up and it struggled and wouldnt start. Finally it fired, I backed it out and it sputtered and died. Hooked up scanner, and it read code P1518.
Pushed it back into the garage and started looking. Couldnt find an issue. I put my hand on the red/blue connectors on the back of PCM and the fuel pump would kick on every time I touched the wiring which definitely sounds like a strange short.
I kept trying to track down the short with no luck.
Now the fuel pump will not trigger, the scanner will not even detect the PCM.
I just checked EVERYTHING. The grounds, the ignition and pos wires, relays, everything. The only thing that I noticed is when I disconnected the red connector and tested some of the pins, some of the ground wire pins read 12v.
I hotwired the fuel pump to see if it would fire with the fuel pump running and it would not.
My wiring harnesses are all new. PSI harness for the LS, AAW harness for the Chevelle. There should not be any issues with the wires themselves.
The only conclusion that I can come to at this point is that my PCM must be fried.
The only things I did to the car prior to it running poorly is hook up my tach, and add an extra ground wire to the passenger side head. I did shift the dash and press down on the PCM to get to something under the dash, but I doubt that could have caused any damage to the PCM.
Heres the story:
The Chevelle has been running great until Thursday night. I went to start it up and it struggled and wouldnt start. Finally it fired, I backed it out and it sputtered and died. Hooked up scanner, and it read code P1518.
Pushed it back into the garage and started looking. Couldnt find an issue. I put my hand on the red/blue connectors on the back of PCM and the fuel pump would kick on every time I touched the wiring which definitely sounds like a strange short.
I kept trying to track down the short with no luck.
Now the fuel pump will not trigger, the scanner will not even detect the PCM.
I just checked EVERYTHING. The grounds, the ignition and pos wires, relays, everything. The only thing that I noticed is when I disconnected the red connector and tested some of the pins, some of the ground wire pins read 12v.
I hotwired the fuel pump to see if it would fire with the fuel pump running and it would not.
My wiring harnesses are all new. PSI harness for the LS, AAW harness for the Chevelle. There should not be any issues with the wires themselves.
The only conclusion that I can come to at this point is that my PCM must be fried.
The only things I did to the car prior to it running poorly is hook up my tach, and add an extra ground wire to the passenger side head. I did shift the dash and press down on the PCM to get to something under the dash, but I doubt that could have caused any damage to the PCM.
TECH Fanatic
Joined: Sep 2008
Posts: 1,643
Likes: 526
No expert but could it be the switched 12 volt or constant 12 volt to the ECM. I had a problem with a harness that the connectors in the fuse block weren't installed properly. Made contact some times. Drove me crazy
Thread Starter
Launching!
Joined: Mar 2012
Posts: 299
Likes: 21
From: Phoenix, AZ
I thought that as well, but I checked that wire and there is 12v going in and out.
[QUOTE]I disconnected the red connector and tested some of the pins, some of the ground wire pins read 12v./QUOTE]
i would start there. follow each of those wires until wherever they are terminated. be it in a sensor, a ground pack, chase em all down. something has melted and shorted to 12v hot.
it takes a lot to kill these PCM's if you cant recover it after you fix the wiring, PM me
i would start there. follow each of those wires until wherever they are terminated. be it in a sensor, a ground pack, chase em all down. something has melted and shorted to 12v hot.
it takes a lot to kill these PCM's if you cant recover it after you fix the wiring, PM me
Thread Starter
Launching!
Joined: Mar 2012
Posts: 299
Likes: 21
From: Phoenix, AZ
Fixed it. The main ground on the back of the cylinder head was loose, even though I had tightened it. I think the bolt was a little too long and it wasn't completely locking the connector to the head. Also the heat shrink was covering part of the connector which wasn't helping the situation. Everything was pointing to a ground issue. I read my PSI harness troubleshooting guide and it said to run a dedicated ground from the battery to the main ground harness so that's what I did and it worked!
I'm glad this all happened when it did because I drove the Chevelle 150 miles to the zip tie drags and I would have been seriously screwed if this happened on the road.
Thanks for the help.
I'm glad this all happened when it did because I drove the Chevelle 150 miles to the zip tie drags and I would have been seriously screwed if this happened on the road.
Thanks for the help.
