RS5 - P2096 Post Catalyst Fuel Trim System Bank1 Too Lean

[forbiddenbeat]

Hey folks, the CEL came on today in my 2013 RS5 with 67k miles. Checked the code – Post Catalyst Fuel Trim System Bank1 Too Lean (P2096). I got this about a month ago, so I cleared it and ran a can of BG 44K fuel system cleaner. But, today it came back on while cruising on the freeway.

Any suggestions? I read it might be the HPFP, which doesn't sound too terrible, but I'm wondering when I should actually have it checked out vs. continuing to clear. Thanks!

[Ape Factory]

Do you have a VCDS? Can you log the post-cat 02 sensor or run a sensor test on it? Could be a few things that cause a lean condition (vacuum leak, exhaust leak, injector or HPFP) or it could be just a bad post-cat 02 sensor. You could switch the two sensors to see if the code moves to bank 2. Additionally, you could log individual injectors on bank 1 to see if there's a misfire problem.

[forbiddenbeat]

Do you have a VCDS? Can you log the post-cat 02 sensor or run a sensor test on it? Could be a few things that cause a lean condition (vacuum leak, exhaust leak, injector or HPFP) or it could be just a bad post-cat 02 sensor. You could switch the two sensors to see if the code moves to bank 2. Additionally, you could log individual injectors on bank 1 to see if there's a misfire problem.

Hey man, thanks for the info. I don't have VCDS, but might be worth getting one (was using my Eurodyne flash unit for my S3 to scan codes :) ). Probably worth the $200 to avoid shop fees for diagnostics in the future – will pick one up!

If the injectors were the issue, wouldn't I also get misfire codes?

[forbiddenbeat]

Just following up on this, the code came back after about a month of driving, along with another code:

2 Fault codes found :
7636 :
Post Catalyst Fuel Trim System Bank1 Too Lean
P2096
Fault status : 11101101
Active
Active at least once in current or last driving cycle
Confirmed
Active at least once since DTC's cleared
Not yet tested in this driving cycle
Warning lamp on

4116 :
O2 Sensor Signal Stuck Rich Bank 1 Sensor 1
P2196
Fault status : 01100101
Active
Active at least once in current or last driving cycle
Active at least once since DTC's cleared
Not yet tested in this driving cycle
Warning lamp off

I've run two cans of BG44K through, so that doesn't seem to be helping. Given both a too lean and too rich code were thrown on the same bank, does that indicate anything?

[JamesRS5]

It’s pointing towards a bad O2 sensor, not an expensive fix.

Obviously check everything else that could cause a rich fault, wiring harness to O2 sensor, blocked air filter, etc.

[forbiddenbeat]

Great, thanks! I did just install an Eventuri about a week ago, so I'll check that as well. This is the first time the rich code was thrown (the lean code has been thrown several times).

[JamesRS5]

Check all the hoses are attached after your intake install.

[forbiddenbeat]

Check all the hoses are attached after your intake install.

Will do, thanks. Dumb question: does the air from the left and right intakes/throttle bodies mix in the intake manifold, or stay separate all the way through?

[Ape Factory]

I've yet to see an upper intake manifold opened up. I did find one single and very partial cutaway of the upper intake manifold and it looks as though there's a divider all the way down the middle. But...I just can't see the air entering on the left and right side, staying separate, and being shot into the intake port via what are really short intake runners. Granted, the RS5 is no torque monster but the runners must be longer than what the external shape of the UIM suggests. Usually, an intake manifold will "fold" the runners into an efficient labyrinth to increase runner length.

In my head I feel like there should be some sort of a main balance chamber which feeds all the runners and would help equalize flow and pumping losses if there's a differentiation between sides for whatever reason. There's two of just about everything except for the MAP and IAT sensor. The MAP sensor is pretty much dead center in the middle of the upper intake manifold's forward edge. There are two throttle bodies because you get velocity at low rpm and flow at high rpm. My guess is air mixes from the left and right throttle bodies inside the upper intake manifold. That's my short answer.

I have to agree with James. Sounds like a bad wideband 02 sensor (pre-cat).

[forbiddenbeat]

Great, thanks Ape!

[forbiddenbeat]

Btw I found this image: http://www.ausmotive.com/images2/Audi-RS5-90.jpg

It looks like the UIM is an open chamber (mixing air from both throttle bodies) with flutes leading into the intake runner.

Side note, but it looks like there there is an intake manifold runner control (the blue valve in the runner) that affects runner volume.

[Vitaliyg]

Hi all , has there been a fix for this ? I have same thing with my 13 rs5 codes p2096 and p2196