CEL Codes Seem Suspicious
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AudiWorld Newcomer
Joined: Jul 2011
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CEL Codes Seem Suspicious
Picked up a 99 A6 Quattro for my brother since he'll be back from overseas soon and needs a car. The car seemed to run fine. After driving it off and on for about 3 weeks the CEL came on. Got it scanned and came up with codes:
P0432 (Main Catalyst Efficiency Below Threshold (Bank 2))
P0411 (Secondary Air Induction System Incorrect Flow Detected)
P1198 (02 Sensor Heater Circuit Bank 1 Sensor 2 Electrical Malfunction)
P1199 (O2 Sensor Heater Circuit, Bank 2 Sensor 2 Electrical Malfunction)
I have researched these codes individually and came up with multiple possibilities. The thing I can't figure out though is why all 4 of these came on at the same time. Would there be something that could go wrong and throw all 4 codes at the same time? I would like to fix properly the first time without throwing parts at it like a couple O2s and a CAT and so on. I have heard that just because a code comes on saying O2 doesn't mean the O2 needs replaced.
Has anyone ever had a combination of these codes thrown at the same time, or know if there is a common issue to cause them all to show at the same time? Any help is appreciated. I'd like to have it running smoothly before he gets back in a couple weeks. Thanks in advance.
P0432 (Main Catalyst Efficiency Below Threshold (Bank 2))
P0411 (Secondary Air Induction System Incorrect Flow Detected)
P1198 (02 Sensor Heater Circuit Bank 1 Sensor 2 Electrical Malfunction)
P1199 (O2 Sensor Heater Circuit, Bank 2 Sensor 2 Electrical Malfunction)
I have researched these codes individually and came up with multiple possibilities. The thing I can't figure out though is why all 4 of these came on at the same time. Would there be something that could go wrong and throw all 4 codes at the same time? I would like to fix properly the first time without throwing parts at it like a couple O2s and a CAT and so on. I have heard that just because a code comes on saying O2 doesn't mean the O2 needs replaced.
Has anyone ever had a combination of these codes thrown at the same time, or know if there is a common issue to cause them all to show at the same time? Any help is appreciated. I'd like to have it running smoothly before he gets back in a couple weeks. Thanks in advance.
Tech Guru
Joined: Oct 2002
Posts: 34,430
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Just because they were all there when you checked does not mean that they were all triggered at the same time. Clearly whoever you bought the car from reset the ECU right before selling the car.
I'd start by checking the SAI system operation, checking for vacuum leaks at the solenoids, and checking the O2's
I'd start by checking the SAI system operation, checking for vacuum leaks at the solenoids, and checking the O2's
AudiWorld Senior Member
Joined: Feb 2009
Posts: 1,138
Likes: 6
I agree - start looking for vacuum leaks. Also, there is a write up in the tech section about how to use a multimeter to check the pins of the O2's to see if they're within spec. That may be another area to start.
AudiWorld Senior Member
Joined: Oct 2009
Posts: 840
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Agreeing with checking vacuum leaks first. Also, fix the secondary air issue first and reset the codes to see if they come again. The check valves are behind the engine and the hose are known to go bad over time.
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