ECM testing & repair...

We have a 2005 Passat TDI Wagon. The ECM is sporadically not sending the ground signal to the N75 valve and it is throwing an underboost and emissions workshop message. It clears itself and can be fine for two days or two weeks before it comes back.
Can anyone recommend where to send the ECM out for testing and possible repair?
Thanks

It's more likely a cut in the wiring loom somewhere, rather than the ECU having any issues. The wire loom for the N75 gets hard and brittle and can slice a wire if its cracked or cut. Last year I had an issue with my car going into limp mode, and upon further inspection, the wiring from the n75 had a cut in one of the wires caused by the sleeving. Spliced it back together and all issues resolved.

If you end up thinking its the ECU its not hard to backup yours. Buy a used one on ebay or go go the junk yard and find one, and buy a BDM tool. Then you can just do a full flash read and write it to the new ecu.

is there a 05 tdi specific BDM tool or are they generic? what's a good one

I should have noted the ECM is definitely the issue. We checked pin 29 to the ECM and when the "emission workshop" comes on there is no ground to the N75 and the ground is fine when the fault is not triggered. At first we thought it was the harness and ran a new circuit for the ground but the issue persisted.

The generic code is P0243 Turbocharger/Supercharger Wastegate Solenoid "A" and it throws the "Emissions Workshop". If it's acting up the code will show as pending after it's cleared and it comes up instantly when you turn the key.
When this first happened in December I found a hole worn in a vacuum hose and replaced it along with the N75 valve but it made no difference and it still comes and goes at random.

afarfalla said:

is there a 05 tdi specific BDM tool or are they generic? what's a good one

Click to expand...

BDM stands for Background Debugging Mode. Any tool that supports this protocol will work. Original tools are best, but for personal use, I'd recommend the latest Ktag knockoffs that are on ebay.

OP, definitely double check continuity in your harness, as well as probe the PWM signal with a scope if available.

QuickTD said:

I'm assuming you have replaced the N75 valve?

Click to expand...

Yes, it has a new N75 valve and there are no vacuum leaks, no leaks in the charge hoses and the turbo actuator moves when vacuum is put to it.
When we initially discovered the the N75 was not getting the ground from the ECM we figured it was an issue with the wiring harness so a new circuit was created by pinning a new ground wire from the ECM to the N75 valve to bypass the harness. It was fine for two days and it started acting up again. We verified the continuity of the new circuit so I'm sure it's not the wiring harness.

http://forums.tdiclub.com/showthread.php?t=491803://forums.tdiclub.com/showthread.php?t=178482

I am interested in who repairs these also, I had same issue with my 2001 ALH. I replaced the ecu and no further problems. Seems there is a diode on that circuit that is in the ecu that may have failed. We did not see any signs of water migration or cracks, some signs of heat though.

http://forums.tdiclub.com/showthread.php?t=178482

Forgot about this one

jmodge said:

http://forums.tdiclub.com/showthread.php?t=178482

Click to expand...

Thank you very much for the links. I didn't think to search the other forums and just stuck with the B5 posts.

You bet, I am never on this forum either, just happened to be nosing around trying to learn a bit about the Passat BV43