P0651

[Rogerbluehat1]

Hello again Audi A6 people!

After you lot pulled an absolute blinder helping me out last time I’m hoping you can again.

My 2012 A6 2.0 TDI has the following issue.

Flashing coil light then into limp mode.This goes away after a restart but happens again.

Eventually this flashing coil
turned into a solid engine/gearbox looking light and went into limp mode. The limp mode cleared after a restart but the solid light stayed on.

I’ve got a basic code reader that gave me 1 code only.

P0651 sensor reference voltage B / circuit open.

Which I believe is just a generic code that would usually be accompanied with other more specific codes?.

The reader has let me reset the code and the light has gone out. I’ve not had chance to drive the car again as I’m at work.

Any thoughts??

[Crasher]

My initial suspicion would be water in the electrics.

[Stuzx61978]

Vcds May bring up other codes, if you know of someone that can help you.

This is complete shot in the dark, but maybe worth checking your egr valve.
I had same symptoms and that’s what it turned out to be.
The seal between the egr cooler and valve had gone, causing coolant water to get into the valve electronics.


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[Rogerbluehat1]

It may well be water somewhere.. it has rained a lot recently[ but not for the last 2 days] and I often get a random rear left indicator warning that goes away on its own when it’s been raining lots. I’ll have a good mooch about tomorrow and see if there’s anything obvious.

I did see a few posts about the EGR valve but they all seemed to have my code and some EGR specific codes too so that’s what’s got me wondering.

Thanks for your input gentlemen and I’ll report back after my drive home from work at 630am 🤮.

[Stuzx61978]

Yeh , I must admit , I have Vagcom and it did show egr fault, so I went straight for that.


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[Crasher]

The left rear light unit issue will be a burnt earth terminal at the light unit which means a new bulb holder and replacing the plug plus fitting a Gold plated earth terminal to reduce contact resistance and therefore heat.

The EGR valves can become contaminated with condensation but a clue to this is a crank speed sensor G28 fault as well.

[Whippy53]

VAG Error Code: 17035/4124/001617
EOBD II Error Code: P0651

Fault Location:
Sensor Reference Voltage 'B' - Open Circuit

Possible Cause:
Malfunction Indicator Lamp (MIL)(K83) active.

Fuse(s).
Wiring/Connector(s).
Engine Control Module (ECM) harness is open or shorted.
Engine Control Module (ECM) circuit poor electrical connection.
Shorted sensor on 5 volt circuit.
Engine Control Module (ECM).

When is the code detected?:
The Engine Control Module (ECM) has detected the sensor 5 volt reference circuit voltage is higher or lower than expected.

[Rogerbluehat1]

Well I only got the flashing coil/limp mode combination once on the way home. When I turned off the ignition I’m pretty sure I noticed a bit more of a judder from the engine, but it might just be in my head after the talk of EGR as I read there’s a judder flap/valve connected to it?!.

Bit strange it only happened once.. I’m wondering if it’s heat related as it’s stop/start traffic all the way to work and pretty much no traffic at on the way home.

How much is a EGR valve anyone?? I’ve ordered a slightly more fancy OBD called Carista that should arrive tomorrow and hopefully give me more of detailed diagnostic.

[Rogerbluehat1]

Well I’ve had a mooch about and haven’t found anything obvious. I disconnected what I think was the sensor on the top of the EGR..

With it disconnected the engine sounds rougher and the shut down was more juddery. With it reconnected the engine sounds better and the shut down was less juddery. So it must be doing something?!. I did notice that after the engine shutdown I got 4/5 clicks from the EGR. Not sure if that’s normal?.

The module in the top left of the engine bay (driver side).. the black cloth tape that’s wrapped around the loom was a bit damp near the module but no water seemed to be in the connector and the pins etc seemed ok.

[Stuzx61978]

This is where I purchased mine.
Had a price from Audi direct with my brothers discount as he works for the group, and it was double that price for exactly the same part.


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