No Communication with TCM, ECM, CAN BUS Failure?

[MicahRutschmann]

Hi all,
I have a 2005 V50 2.4i that has been giving me trouble recently.
After sitting over a weekend, I washed the car and the next day it refused to start. I got 'Immobilizer See Manual" and "Anti-Skid Service" on the dashboard. It unlocks the steering and lets me retrieve my key. I've chased bad connection at every module, CEM, ECM, etc, I have zero water ingress on the CEM and every fuse seems intact and clean. Also I'm using a new battery to rule that out.
Hooking up to VIDA I have zero communication to ECM and TCM. I have power, ground at the ECM, switched gound at the main relay back to the ECM.
Currently I'm suspecting either a faulty ECM or CAN failure. Probing pins 6 and 14 on the DLC I have 118 ohms, which makes me think there is an open circuit somewhere in the network.
One question I have for anyone who knows CAN is which modules contain the 120 ohm terminating resistors? That would help the troubleshooting.
I'm a total novice to VIDA and CAN networks and am learning on the fly here to try and get this wagon rolling again, so any insight would be greatly appreciated!

[scot850]

While I cannot really help on the electrical side too much, if you read my thread on the 07 C30 T5 on this forum, you will see the challenges I have had and are still having with this car. That includes access issues with Vida, but I have no access issues seemingly with my Autel 802.

This car has had so many potential causes for electrical issues from leaking sunroof drain on the front RHS where the CEM is, a mechanic damaging engine wires and not reattaching the maim engine ground causing the battery to be fried and possible ECM/CEM damage. Also add leaving the main fuse box lid missing over winter and it getting sprayed with salty road water. Trying to figure this one is got me pulling my little remaining hair out. The car is now back at the dealer as they thought they had fixed it.

Do you have the wiring diagrams for the car? I think I linked to a source in that thread on the C30.

Good Luck!

Neil.

[MicahRutschmann]

It's a quick turnaround on this one, but it's finally fixed. After hours of tracing wires in the CAN system I finally found the culprit. Over the weekend the car sat it seems a rodent had made a meal of my wiring harness behind the battery, next to the BCM. Both wires in the CAN system running from the cabin were chewed completely off, explaining the lack of communication between modules on VIDA. Spliced the wires together and, pesto, she roared back to life, zero faults on the dashboard! Finally have my daily driver back online!
Now I can spend my evening doing something other than studying wiring diagrams..

[MicahRutschmann]

While I cannot really help on the electrical side too much, if you read my thread on the 07 C30 T5 on this forum, you will see the challenges I have had and are still having with this car. That includes access issues with Vida, but I have no access issues seemingly with my Autel 802.

This car has had so many potential causes for electrical issues from leaking sunroof drain on the front RHS where the CEM is, a mechanic damaging engine wires and not reattaching the maim engine ground causing the battery to be fried and possible ECM/CEM damage. Also add leaving the main fuse box lid missing over winter and it getting sprayed with salty road water. Trying to figure this one is got me pulling my little remaining hair out. The car is now back at the dealer as they thought they had fixed it.

Do you have the wiring diagrams for the car? I think I linked to a source in that thread on the C30.

Good Luck!

Neil.

Hey Neil, sounds like you've had a hell of a time with yours. Have you tried looking into the CAN system? Checking resistance at the OBD port is quick and easy, and can tell you a lot about your onboard modules and wiring harness integrity. If you don't have good news from the dealer I'd definately get a multimeter on it to see what you've got at the OBD outlet. Check out ECM TESTING on Youtube, they've got a great video about multimeter tests for the CAN system. Here's a link to the video:



Hope this helps,
Micah

[scot850]

That is good information. I will spend some time watching the linked video you have listed above. I have given all the info I have in terms of what has failed at what point in the process to the dealer and their mechanic on this job. We can only hope, and should the dealer not be able to fix the issue, I hold no bad feelings on this with them. They have already gone way over and above. Thank you. I hope you have more luck. I am hoping the issue is not the CEM or ECM being damaged by the alternator overcharging when the main engine ground was not reconnected by the repair shop mechanic.

I have suitable ECM and CEM donors that can hopefully be used by Xemodex to clone if needed.

Neil.