Help, I need a GM Tech Expert
Thread Starter
Burning Brakes
Joined: Sep 2001
Posts: 1,173
Likes: 1
From: Aguila AZ
Help, I need a GM Tech Expert
I have a very difficult problem with the data link on an '03 C5 vert. I cannot get codes because I get the following DIC messages:
PCM No Comm.
TCS No Comm.
RTD No Comm.
BCM 5 codes indicating a loss of communication
I have the GM manuals and have used that to conduct the following checks:
1. I have verified all grounds and power to the PCM and other items.
2. I have cleaned and inspected all body grounds and splice packs.
2. I have checked all fuses.
3. I have verified continuity of the data link from the DLC to the PCM.
4. I have replaced the PCM and the traction control computers with the same 'No Comm.' results.
I suspect a problem with the under dash wiring harness. This car was damaged in a fire and I have replaced all wiring harnesses. I had an under dash harness from a 2000 MN6 installed and I did not have the 'No Comm." issues with the 3 computers. I then replaced this harness with an '03 A4 harness to be compatable with the A4 trans wiring. Now I have these 'No Comm." issues.
I need to talk to a knowlegable GM tech for help. Can anyone recommend such a person?
Thanks
Shirl
PCM No Comm.
TCS No Comm.
RTD No Comm.
BCM 5 codes indicating a loss of communication
I have the GM manuals and have used that to conduct the following checks:
1. I have verified all grounds and power to the PCM and other items.
2. I have cleaned and inspected all body grounds and splice packs.
2. I have checked all fuses.
3. I have verified continuity of the data link from the DLC to the PCM.
4. I have replaced the PCM and the traction control computers with the same 'No Comm.' results.
I suspect a problem with the under dash wiring harness. This car was damaged in a fire and I have replaced all wiring harnesses. I had an under dash harness from a 2000 MN6 installed and I did not have the 'No Comm." issues with the 3 computers. I then replaced this harness with an '03 A4 harness to be compatable with the A4 trans wiring. Now I have these 'No Comm." issues.
I need to talk to a knowlegable GM tech for help. Can anyone recommend such a person?
Thanks
Shirl
Drifting
Joined: Oct 2003
Posts: 1,540
Likes: 0
From: bloomfield nj
have you checked the 2 connectors near the bcm?these are the data communication junctions for the control units.can you communicate with the sim unit[airbag]?if all the fuses,etc.check out,the only other thing i can think of,is 1 controller pulling the data bus down.
Burning Brakes
Joined: Jul 2001
Posts: 766
Likes: 0
From: Oregon
It sounds like the Data line might be grounded. Possibly a short to ground on the data line, or a bad module pulling the line to ground. Try disconnecting each data line individually @ star connector #1 to see when everything comes back. Let us know
Last edited by HurricaneZ; Jan 6, 2005 at 11:21 PM.
Thread Starter
Burning Brakes
Joined: Sep 2001
Posts: 1,173
Likes: 1
From: Aguila AZ
Latest update:
Well, I have solved part of my problem. As mentioned, I had replaced all the wiring harnesses. I found two inline connectors that were reversed. I didn't think any connectors could be plugged in wrong, but I found out that some can. I now have communication with the PCM. Still 'no comm." with the TCM or RTD yet. I also discovered that my engine harness is for a MN6 and it does not have the connector for the A4 controls. This will be a major headache and expense to replace.
So, progress is being made. Thanks for your input.
Shirl
Well, I have solved part of my problem. As mentioned, I had replaced all the wiring harnesses. I found two inline connectors that were reversed. I didn't think any connectors could be plugged in wrong, but I found out that some can. I now have communication with the PCM. Still 'no comm." with the TCM or RTD yet. I also discovered that my engine harness is for a MN6 and it does not have the connector for the A4 controls. This will be a major headache and expense to replace.
So, progress is being made. Thanks for your input.
Shirl
