CEL issues on B6 S4 relating to post cat

[UnstableOS]

Here is the deal... I also have a thread running on QW relating to this topic but want to check if the community here may have some ideas..

CEL comes on anywhere from 65 to 100 miles.. Codes both are referencing post cat failures... One engine bank running lean and one running rich.

Exhaust setup is APR downpipes and magnaflow the rest of the way back. I did se that APR replaced the cats in their downpipes back in Dec 07, so I wonder if there was a similar issue with the older cats. Anyone remember hearing of post cat issues with the APR downpipes or have any idea what could be going on?

All sensors appear to be fine as well as injectors so the CELs keep bringing us back to the exhaust system..

[UnstableOS]

Bump

[nimski62]

Need EXACT CEL. Running rich and catalytic converter efficiency are 2 completely different things.

[UnstableOS]

P2097 and P0298

P2097
Description:
BBPost catalyst fuel trim system too rich bank 1

Explanation - BBFailed fuel pressure regulator

Probable cause - Failed fuel injector

P2098
Description:
BBPost catalyst fuel trim system too lean bank 2

Explanation - BBLean Air/Fuel Ration - check fuel system

Probable cause:
BB1 Vacuun leak on engine
BB2 MAF Sensor Fault
BB3 - Air leak near sensor or failed sensor

[Justincredible]

Is this what the VAG showed you? just post the Vag data that came up and nothing else if you can. The rest if added is not helpful

Just straight 100% vag info

[UnstableOS]

18529
18530

[Justincredible]

ok it took me a few seconds to figure out what you did and why you were posting the other info.

Ebahn....got it. This is what threw me off

P2097 and P0298

P2097
Description:
BBPost catalyst fuel trim system too rich bank 1

P2098
Description:
BBPost catalyst fuel trim system too lean bank 2

Explanation - BBLean Air/Fuel Ration - check fuel system

It looks..obviously like there is one side too rich and one side two lean. First would be to check the intake and see if there are any Vac leaks. The leak could be in one of the Vac lines or the System after a check Valve some where. But if you can hold iddle fine at any given RPM below 3000 I would say its not a Vac leak.

It could be several things but the check list looks to be the same thing I would say.
Check the fuel filter altho I don't think that would just effect one side of the motor. The MAF could be bad but..I don't know. Sounds like there is just not a straight issue but something more quirky that is off

[nimski62]

I have been dealing with these same 2 codes.. I think it's due to burning oil? idk im tired of this car.

[Silver B6 S4]

I have been dealing with these same 2 codes.. I think it's due to burning oil? idk im tired of this car.

How much oil are you going through?

[nimski62]

1qt/ 6-700 miles.

[Silver B6 S4]

1qt/ 6-700 miles.

Sorry for the thread jack, but what oil are you using? PM me if you want, Alex.

[UnstableOS]

I have been dealing with these same 2 codes.. I think it's due to burning oil? idk im tired of this car.

Do you have aftermarket exhaust? If so what setup?

[homeychan]

I also have those exact codes after having my engine replaced for oil consumption (http://audiwarranty.blogspot.com). My car is in a shop right now trying to figure out and I will post the results when done, hopefully I will know tomorrow. My car has AWE Cat back, but that should not throw a code.
For the oil consumption guy - my car had oil consumption issues (3.74 pounds of oil every 800 miles). When the oil light comes on it’s more than a quart down. Replacing the short block and some head maintenance seemed to have cured it; short block is about 10k though + labour. My AC also no longer works, and I can’t wait to find out how much for that!

[UnstableOS]

I also have those exact codes after having my engine replaced for oil consumption (http://audiwarranty.blogspot.com). My car is in a shop right now trying to figure out and I will post the results when done, hopefully I will know tomorrow. My car has AWE Cat back, but that should not throw a code.
For the oil consumption guy - my car had oil consumption issues (3.74 pounds of oil every 800 miles). When the oil light comes on it’s more than a quart down. Replacing the short block and some head maintenance seemed to have cured it; short block is about 10k though + labour. My AC also no longer works, and I can’t wait to find out how much for that!

Sounds good thanks. Sorry to hear you are having so many problems..

[homeychan]

I am still waiting for the full report back but in a short conversation with the service centre I need 2 oxygen sensors. I should have the full breakdown tomorrow AM and costs, my AC is also broken and I my estimate is 2k, lets see how close I am.

[UnstableOS]

It's not the sensors dude, I can almost guarantee it.. What exhaust are you running?

I've swapped in sensors and it still throws the same codes.. The issue we are experiencing is one of three things based on my research...

1. Small vacuum leak - unlikely if you are holding revs
2. exhaust leak - had it but CEL comes back even after correction
3. Ox sensors may need to be placed behind forward cats

Are you experiencing fuel trim codes? Originally I had one engine bank running rich and one lean, corrected exhaust and now I am running both lean according to base scans. No real way to tell until I get onto a VAG on SAT morning, but my dollars are on exhaust related issues...

[homeychan]

I just got off the phone with the shop and you are right. It turns out that when the mechanic put the engine back in the car, he put them on the wrong sides. The pre cat sensors are correct but the post sensors are reversed. I guess they have done extensive testing and have verified the sensors are reversed. This job books at 10 hours to fix, so I am going back to original dealer to see if they can cover this N/C. AC appears to need a pressure valve and that costs $400, may need a compressor but needs the valve for sure. I may as well replace the sensors if the job is so big anyways, so I will get 2 new oxygen sensors. This car is going to send me broke.

[homeychan]

Oh yeah - I have an AWE Cat back.

[UnstableOS]

I just got off the phone with the shop and you are right. It turns out that when the mechanic put the engine back in the car, he put them on the wrong sides. The pre cat sensors are correct but the post sensors are reversed. I guess they have done extensive testing and have verified the sensors are reversed. This job books at 10 hours to fix, so I am going back to original dealer to see if they can cover this N/C. AC appears to need a pressure valve and that costs $400, may need a compressor but needs the valve for sure. I may as well replace the sensors if the job is so big anyways, so I will get 2 new oxygen sensors. This car is going to send me broke.

Sensors reversed, really? How is it 10 hours to reverse sensors?? My tech says that 10 hours is ridiculous.

[homeychan]

Maybe I am getting sold a bill of goods but these guys say 10 hours is what it books at and I may as well replace with new sensors. Either way it is now going back to the original dealer on Wednesday and they will correct the problem no charge. I am just happy I don't have to pay for it. What does you tech say it should take?

[UnstableOS]

He says for a sensor swap and intake cleaning like 2-3 hours.

[homeychan]

Well thats good information and thanks a lot, I am going to ask what would take 10 hours when I pick the car up. I am scheduled to drop it off next week on Wednesday to the Audi dealer and will update if that fixes the CEL.

[UnstableOS]

Sounds good. Keep me posted. I may have my sensors swapped Friday to see if my CEL issues clear up..

[homeychan]

My car is still at the dealer, did you swap your sensors around? Dealer agrees with you and problem is only 3 to 4 hours. Replacing sensors books at 5.5 hours.

[UnstableOS]

My car is still at the dealer, did you swap your sensors around? Dealer agrees with you and problem is only 3 to 4 hours. Replacing sensors books at 5.5 hours.

Was at dealership yesterday.. After diags they told me "there are no issues, the CEL is due to the exhaust"... I said thanks, I already knew that and refused to pay them for the diag.. as there was no solution according to them.

[B6guy42]

Not to get off topic, but doesn't it almost seem like when something goes worng with this car (chain driven everything less alternator) its like 10 hours of labor to fix? ALLDATA posts 11.5 hours R+I of the motor. Why not just get a new motor every time? LOL

[homeychan]

Yeah that sounds about right, but a new motor (short block) is 12k, so not very affordable. I just found out to replace the AC compressor they have remove a part of the motor, I guess the Audi manual says remove motor.

back on topic - Still working on CEL issue, they have to dismantle most of my car again for the compressor and will look into the CEL then, I gues they also originally said 3 to 4 to check the sensors but have now recanted and said it is a big job to remove the exhaust and everything to get to them and test. Ironically about 10 hours, same as removing motor but i already have a new motor!

[jfunkey]

Was at dealership yesterday.. After diags they told me "there are no issues, the CEL is due to the exhaust"... I said thanks, I already knew that and refused to pay them for the diag.. as there was no solution according to them.

what? still trying to make sence of this. Did or are you going to still put in new 02's? Still the same codes when they come back?

[UnstableOS]

what? still trying to make sence of this. Did or are you going to still put in new 02's? Still the same codes when they come back?

sensors are fine, I am at a loss...dealership service said they have no idea or solution and just state it's because of the exhaust.. Maybe I'll try another dealership service center or try the JHM spacers.

[Audi0s]

Maybe the computers confused because the cars not as "clean" as it should be due to the aftermarket cats, flow is different as well. A hole in the exhaust will also show as catalyst efficiency or lean running. An easy way to test for a vacuum leak is to spray brake clean on any intake tubing. If the idle changes, you found it. Listen closely for the whistle of an open line Do you know how many pins the connector is? You can measure voltage by back probing, you need a graphing meter though, I dont think theyll pick up the change otherwise.

[UnstableOS]

APR (have APR DPs) is going to provide me with a stock ECM update that includes test pipe tuning to eliminate the CEL.. At the time of update I'll have the tech run some VAG scans to validate the correction and be sure I am not running lean/rich..

[homeychan]

Well I just got mine back and the dealer had the exhaust off the car and some major disassembly to change the AC compressor (who knew service manual said remove engine to change compressor). Dealer said they where not installed incorrectly, tested good, checked wiring and all wiring was good. They replaced sensors, CEL usually comes after a couple days though, so have to wait and see. Got a catastrophic flat after leaving dealer, I think this car is possessed.

[homeychan]

Did your problems go away? My dealer said the O2 sensors were not reversed, but replaced them anyways N/C. I got the car back with code cleared but after 2 days of driving it came back. I have stock cats, just a cat back exhaust. Does anybody else have any ideas? Dealer said may be a problem with Cats and they are covered till 130,000kms.

[homeychan]

Looks like I am the only one posting on this one still but I will update it, just in case somebody else has the same problems... Dealer says cats are plugged, so are going to warranty. This is supposedly what is causing the CEL, I will post after the replacement if successful.

[homeychan]

Hey guys, any of you experts out there can help me? I just had the engine replaced for oil consumption and and then put on the Cat backs, but the car throws P2096 and 96 codes 1 for right and 1 for left, one is too rich, one is too lean. Dealer has replaced oxygen sensors and one cat. Still get same codes. I had one garage tell me the oxygen sensors were reversed, but dealer say they confirmed they are not. Dealer is now saying it must be the exhaust, but that does not make sense since the cats are stock. Any input?

[homeychan]

Car is back in for the CEL again, one Cat replaced, both O2 sensors. Hopefully we'll have something new to report soon. Hopefully the car wont have to go in for service for a long time after this.

[homeychan]

If anybody is interested, looks like O2 sensors are reversed post cat, they are in correct mounts (from service advisor), but reversed right to left. Waiting to see if problem is finally resolved, have had the loaner for 6 or 7 weeks now.

[homeychan]

Here appears to be the complete solution from the service writer, I have not been to see the mechanic yet. Post Cat sensors crossed, 1 Pre Cat sensor failure, thermostat failure, coolant actuator stuck so car never came up to operating temperature.

[homeychan]

***Official resolution*** Oxygen sensors reversed, in correct connectors, but in wrong side. Side issue: Coolant actuator stuck open car would not come up to operating temperature, possibly contributed to codes, since once it was fixed a different code appeared.

[ngng]

did you accidentally reverse the sensors?