ybaudist

Hi, everyone.

I've got these readings using my VAG-COM, but I don't have a repair manual just yet.

Here are the codes:

17585 P1177 35-00
Bank2: O2S (Lambda)Correction Behind Catalyst: Control Limit Reached

17584 P1176 35-00
Bank1: O2S (Lambda)Correction Behind Catalyst: Control Limit Reached

16885 P0501 35-10 Intermittent
Vehicle Speed Sensor Range/Performance

16891 P0507 35-10 Intermittent
Idle Control System RPM Higher Than Expected


Can anyone help interpret these or direct me to the right place? I've done some research, but found nothing as far as repairs go.

I'm guessing I need some new O2 sensors (but which ones? before the cat, or after, or all 4?)

I can also check the wiring to the speed sensor.

Other than that... ??? What about idle being higher than normal? What repairs go with that?

Any useful insight is highly appreciated.
Thanks, guys.

ybaudist

^ ^ ^ 2000 A4 2.8 QM Stock (engine code ATQ) ^ ^ ^

Shard7

The likelihood of both O2 sensors failing in the exact same way at the same time is pretty slim, so I think those codes are indicative of a problem affecting both banks. Vac leak would also result in higher idle rpms since additional air is getting into the intake manifold.

Ertman

Post cat o2 sensors

ybaudist

Shard7 has a point. They can't go at the same time... unless, you experienced that and know for sure that that's a fix. And how do I check for vacuum leaks? Visually, it looks ok. All vacuum lines are intact, and the engine idles normally (just shaking slightly)...

Do you know a good place to get the post cat O2 sensors for less $$$?

Shard7

A lot of OBD codes can be a bit misleading. The code may be set due to an odd value from a given sensor, but that may just be the symptom of something else that's wrong.

If you have a VAG-COM, you can locate vac leaks with a propane torch (do this carefully in a well ventilated area). With the engine running, use the torch (unlit) to add a small flow of gas to various parts of the vac system and intake manifold. If there's a leak, the gas gets sucked into the system and you'll see a change in the pre-cat O2 sensor values due to the increased richness.

If you can read out your long term fuel trims using a VAG-COM, that would be some helpful info.

ybaudist

but I will try when I get home tonight (or sometime later this week). If you know the 409.1 version is capable of that, let me know, so I can just read the long term readings without having to set my car on fire

THNX.

Shard7

Not familiar, but even a basic OBD II tool should be able to do it since trims aren't VAG-specific

Ertman

if not, it will not let you read above block 25. Long term fuel trims are block 32.

Ertman

it may clear up some of your problems, or at least pint your in the right direction. As for my post cat o2 sensor response, I was merely pointing out that B1S2 and B2S@ are post cat sensors.<ul><li><a href="http://www.ross-tech.com/vag-com/cars/fuel-trim.html">fuel trim info</a></li></ul>