Replace Entire 2.0T Engine Wiring Harness?

[tywoodruff]

I have a 2007 A4 2.0T Quattro Manual. I've had a misfire in cylinder 4 for months, CEL code P0204. I switched the plug and coil pack to cylinder 2 and the miss didn't follow. The other day I saw someone in a forum with a 1.8T complain about a misfire, distorted speakers, problems with the window controls, and other random issues. He decided there's short somewhere in the engine wiring harness / loom. Lately my speakers have been distorted and I recently had issues with one of my window controls for a few days. I've also been getting a P0506 code but I'm assuming that's because the misfire is causing it to idle so roughly. So, I just ordered a used wiring harness (part# 8E1971074GA) for $65, seemed cheap enough compared to the $1400 for a new one. Has anyone replaced the entire harness? Can it be done in a day?

[RakkCity]

I... Doubt it would be done in a day. That sounds like a major pain in the ass tbh.

Have you checked compression on the misfiring cylinder?


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[Okedokey]

Just make sure you test the 'new' harness completely before you install it.

[aluthman]

I'm sure it could be done in a day. It's actually not all that difficult to just pull the old one and put in a new one. Once you start talking under dash wiring, it becomes a nightmare fast.

[APR_Fast]

Did this on my old b6 1.8T USP. It wasn't that bad at all. Plus the whole harness was on sale for $200 from audi and the b6 1.8t are notorious for chewed up wiring. Just remember, there's only one length to each connector from the harness so if you don't have enough length or too much length it's probably not the right connector. The hardest part was getting the harness out from the back of the engine but if you're methodical and take your time it's not too daunting of a task.

[tywoodruff]

Thanks y'all. I plan to label the old one as I take it out. The biggest problem I see so far is getting my wiper off. I've already cracked the windshield prying against it. I've even used a puller. I'm gonna start putting some WD-40 on it for a few days.

[p0isin]

One full day might be enough time if you have a Bentley manual or if you're familiar enough with the car. Just take it 1 step at a time and take pictures or document progress some other way.

For the wiper you need to unscrew the nut, thread it a couple times and then hit the nut while pulling on the wiper blade. Then it will pop off. Don't just pull.