P0151 Fault code on RS5

A5/S5/RS5
#1

Has anyone had to deal with a P0151 fault code on the RS5?

O2 sensor 1 on left bank. (B2)
Did a reset when the CEL first came on then I got 3 related faults the second time…
In addition to the P0151 coming back, I got the following:

P2254- Oxygen sensor B2 S1 negative lead open circuit…
and
P0150 O2 B2 S1- malfunction in circuit.

All wires seem to be intact and all fuses are good. TBH, I do not have an owners manual so I’m not sure which is the exact fuse to check.

You guys think it’s worth getting an owners manual?

Anyway thank you in advance

#2

You got a owners manual on CD? I guess not since it normally sits in the folder containing the manual, but in case you do it might be installed on your on board computer. Don’t have the owner’s manual at hand.

I would gamble on it being related to the exhaust not being sealed not sure why you are not getting system too lean. I will get the latter when running e85 due to its higher oxygen content. I would try different fuel/cleaner additives.

#3

Yea do not have the CD or the book. Are you saying it could be installed on my car computer?

The joints where my down pipes connects has had a small leak for way over a year. I imagine it’s only when it’s cold. Not sure how a leak there would affect the pre cat O2. The O2 fault came on a few days ago.

#4

Get on myaudi (dot) com and create an account there. There, at least before they updated it, you could read the on-board manual in various languages.

If it is recent I would maybe too much oil or just the wrong fuel triggering it. I would try new fuel.

#5

The other thing that has been mentioned is low voltage. Have you checked the battery with VAGCOM?

#6

Or the PCV valves I heard, on the S4/S5 3.0. Listen for vacuum leaks.

#7

With each passing ehaust pulse, there’s a vacuum created behind it and it can actually suck in air from the outside when the flange isn’t sealing. I think I have this issue as well and I need to get under the car to check it out. As the exhaust heats up, the metal expands and seals. I don’t have the code but she now prefers to be warmed up for a minute. After that she purrs like a V12.

#8

So the P0151 code pointed to just the O2 sensor. The pre cat O2 on the driver side. I replaced It and the CEL went away. As of now, No fault codes have returned in a few hours of driving.

Wouldn’t my leaking exhaust damage tHe O2 sensor Closes to it if it were the cause of the problem?

#9

Glad it is now fixed then. You can get to it without pulling the engine right? It looks like it is possible to do both at least on the passenger side but difficult to get to.

What did it look like, clogged with oil? I

#10

I removed the TB (do I need to run adaptation on this? I didn’t) but I probably didn’t need to, the main thing that was in the way was a combi valve which when removed allowed straight access to the pre cat sensor.

Sensor was black but not oily and not overly sooty. The cat though was heavily chipped in many areas but looked completely clean from any carbon.

1 Like
#11

A certain well known Mr ApeFactory has a video on it.

#12

It’s not a bad idea to run adaptation any time you have them out or you’ve cleaned them! Can’t hurt.

#13

If you need to replace the Pre-Cat O2 sensor the Bosch part is 17225, you can get them for $100 rather than paying the Audi mark-up.