P0471 Error Code - Exhaust Pressure Sensor? - A4 B7 2.0Tdi 140bhp Cabriolet

[davidmbell]

Hello all,

I have a 2007 Audi A4 B7 2.0Tdi Cabriolet - 140bhp - i believe this to be the BPW engine?

Got the Check Engine light on a few weeks ago. Didn't have chance to do anything with it, but a few days letter seemed to just go off again.

No real obvious symptoms? Although very ocasionally seems as if the power almost dips, and sort of feels like a missfire - tends to be when just feathering throttle to keep at a fixed cruising speed (say 50 zone on the M1!)

Anyway, scanned with my basic ELM scanner and a stored code of P0471 showed. So cleared/erased the code, and nothing more for a few weeks.

Till yesterday, when the CEL/MIL came on again, after a day of driving, and I'd just stopped for 20 mins and then restarted - the CEL/MIL light came on again. So, scanned again and same code.

A google search suggests its the Exhaust Pressure Sensor - but lots of things calling it DPF sensor. Now mine is of the age/engine size that it doesn't have the DPF, but it definately has this same sensor, mounted to tbe bulkhead back left of the engine bay.

Part no on it is "07Z 906 051A". I removed it and checked nothing obvious (cracked, full of crap, wires, hoses all ok etc)

Is it likely to be this sensor that's gone duff?

If I clear the error within a few engine stop/starts I see in my reader software a "PENDING" TROUBLE CODE P0471 - but the CEL/MIL light hasn't actually come on (yet)?

Do the symptoms sounds like it could be this sensor? Why would my car have this sensor if it isn't a DPF car?

Finally, I do also seem to get a very lumpy idle sometimes when coming to a halt - only for a few seconds the whole car seems to wobble and then it settles itself?

PS done 153,000 miles so no spring chicken!

ta,

David

[arman123]

It should have a dpf unless it was removed

[davidmbell]

When mine was built you had to specify DPF, and the DPF cars were 16v, the non DPF cars were 8v.

I thought mine was the 8v BPW, non DPF engine. (See Audi A4 - Wikipedia) "here were two different versions – one had an 8 valve cylinder head the other had 16 valves. They had the same power and torque output and performed equally. Customers could not choose directly between those two engines. They got the 16-valve version when they ordered the DPF otherwise they got the 8-valve version. In many countries the DPF became standard equipment for all B7 diesel engines from model year 2006 on and the 8-valve engine was no more."

But having checked the label inside the spare wheel well it says "Cabrio 2.0Tdi 103KW DPF M6S"

It's now vibrating horribly at idle when warm (not when cold) so I am thinking I've got an injector on it's way out. Whether this is connected to the other error message not sure. It's hopefully going in next week to someone who's ex Audi guy who has full VCDS to see what's up.

[RSWilson]

Hi, Bit of info and a question as this thread is so similar to my question.
My EML came on and I suspect my pressure sensor is faulty.
I have just bought one for about £12 from ebay.

Prior to buying this sensor I bought a can of MANNOL foam DPF cleaner (from ebay) and I sprayed the foam down the larger bore of the two pipes in the hope that this foam went in before the DPF.
I would be interested to know if anyone can confirm which of the two pipes is pre filter and which is post filter.

pressure sensor.jpg

My advice to the OP would be to unplug the MAF and see if the idling improves. I don't know if the idling would be caused by the sensor however I imagine if the DPF is blocking this may show in this way - but I'm guessing. I have heard however that these sensors are a fairly common failure point hence at £12 I figured I'd swap it. it is very easy to do on my 2009 2.0TDi Final Edition as it is mounted on the bulk head.