08' A4 Multiple overlapping electrical gremlins

[rollerton]

Ok guys -
Hows' it going. I'm helping a friend with his 08' A4 and some problem that have recently popped up. Pretty low mileage car ~ 75k I think, and other than a tune and some exhaust work totally stock. Well, also had aftermarket stereo.
Basically- about 3 weeks ago out of nowhere he says his windows started acting up. My advice first was the door jamb of course. So he found a few cracks in the wires, none totally broken. Repaired that and did not fix teh problems. It evolved from intermittent window drama to NON-working:
1. Windows
2. Remote
3. Mirros
4. Stereo
5. Odometer
6. Turn signals
7. Wipers
8. Cruise control
9. Glitchy headlights.

I have a trusty old Hex-can and did some sleuthing and it initially looked like the Central elect. / PCM had failed; that and the cruise were the 2 that showed no communication. Seemed to make sense, so swapped out the Cent Elect module (behind fuse panel). This didn't get us anywhere. Still unable to comm with it. And subsequently can't talk to the Comfort Module (under the seat); So swapped that out also; no evidence of any water intrusion anywhere.
No improvement.
At this point No comm with Central electrics and Comfort module, or steering wheel now that I think about it.. and all those things continue to NOT work properly. One thing that may matter is the Engine says no comm with Cruise control module~ though that could mean errors preventing data or bad module. I'm not sure the cruise would create enough static to foul the other modules.
I'll also add that *occasionally* they all just start to work briefly.

Where would you look next?

[a4audi4fun]

Battery condition?; seems like a lot of electrical issues.

[rollerton]

Battery condition?; seems like a lot of electrical issues.

Not sure how new it is, but fully charged. No charging issue.
Yeah-- its definitely a bunch of stuff. And I'm usually fairly good at that kind of thing, but neither of the usual suspects seems to be the problem...so I'm kind of stuck. Just going to start unplugging modules and fuses I guess?

The real ****** is that it occasionally just all works for a few minutes.

[FatMongo]

You might want to check out your J519 module to see if it shows any signs of water intrusion. Its located under the steering wheel after you remove the under panel on the drivers side. They typically get wet due to clogged drain holes in the firewall and cause weird electrical issues.

[rollerton]

You might want to check out your J519 module to see if it shows any signs of water intrusion. Its located under the steering wheel after you remove the under panel on the drivers side. They typically get wet due to clogged drain holes in the firewall and cause weird electrical issues.

Yeah- that's the central electrics/ PCM. We replaced that already.

[Theiceman]

Can you talk to engine, seat belts and and abs only ?
Those are on the can bus, everything else is in the K-line if that helps.

Sent from my SM-G973W using Audizine Forum mobile app

[Zolli]

To me, this sounds like a ground wire(s) problem. Man, I hate electrical gremlins. I can’t imagine the little terrors that Priuses and Tesla’s will be when they get on in age.....

[rollerton]

Can you talk to engine, seat belts and and abs only ?
Those are on the can bus, everything else is in the K-line if that helps.

Sent from my SM-G973W using Audizine Forum mobile app

Yep. I've been reading around and came to the same conclusion. Sounds like K-like short or something..

So, try unplugging all K-line modules one at a time until stuff starts waking up I guess?
He has an aftermarket stereo abut never had a problem....But that's always a likely suspect.