Check Engine Light Due to Vacuum Leaks, Oxygen Sensor, or Catalytic Converter Fault on Audi A4 Quattro

Vacuum leaks, oxygen sensor failure, and catalytic converter efficiency faults can cause the Check Engine Light to illuminate.

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Average mileage: 124,298 (56,000–210,000)
Exhaust & Emissions affected: 1.8L 4 Cylinder Turbo
10 model years affected: 1997, 1998, 1999, 2000, more2001, 2002, 2003, 2004, 2005, 2006
60 people reported this problem
26 people shared problem details
2003 Audi A4 Quattro110,000
I have had my check engine light on for last month. The mechanic at the shop put the computer on it and it says bank 1 lean and mis fire on pistons or something like that? The car runs fine but ideals rough.
11 people like thisFlag inappropiate
Vacuum leaks indicated by codes. Dealer and outside mechanics used vapor sniffers to locate a problem but found nothing. After doing my own research, I tried replacing the N80 valve and the problem was fixed. A symptom of a bad N80 valve is that when fueling up the car, the engine will hesitate when starting because of the vapor backup in the failed N80 valve. A replacement can be found for around $25 and installs fairly easy.
4 people like thisFlag inappropiate
Replace vacuum hoses
3 people like thisFlag inappropiate
check engine light came on - catalytic converter insuffiency - replaced converter and check engine light has come on again after 1,300 miles with new converter. Obd has to be read again. Vehicle seems to be running okay.
3 people like thisFlag inappropiate
2002 Audi A4 Quattro140,000
catalytic converter and left side blinkers
2 people like thisFlag inappropiate
2003 Audi A4 Quattro151,000
Check engine light on. Went to Auto Zone to get a reading and the codes read that it can be a faulty turbo, catalytic converter or an air leak.
2 people like thisFlag inappropiate
The check engine light remains on. Replaced gas cap about 2 years ago. I have worn hose, that probably is leaking air. Not sure how to affect repair myself. The problem seems to be effecting my mileage performance now.
2 people like thisFlag inappropiate
2002 Audi A4 Quattro135,000
Check Engine Light - Replaced Sensor, Catalytic Converters, Manifold Runners, Won't Pass CA Smog
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1998 Audi A4 Quattro140,000
My Audi has all the same problems.
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2004 Audi A4 Quattro114,000
There's not too many details. We bought the car yesterday and last night the check engine light came on. Saturday night meant a quick detour to Auto Zone and the code read for the catalytic converter. We're concerned also that the 75000 mile timing belt was not changed (dealer said the service records were lost and there was now telling). Our efforts to find a solid, used and affordable car seem doomed; it's a pretty grim morning.
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1999 Audi A4 Quattro192,000
my check engine light is on all the time but my vehicle runs good and the comes when the check engine light star blinking my car start chaking alot
2006 Audi A4 Quattro184,000
this problem has been an issue for 4 years and 80000 miles even audi couldn't figure it out and just reset computer and I drove to another local garage and they inspected and passed it
2000 Audi A4 Quattro106,000
No solution as of yet but my check engine light just came on today with the coolant light. The coolant has been refilled but the check engine light is still on.
1998 Audi A4 Quattro142,000
same engine light and codes read catalytic converter both sides and evap leak
2004 Audi A4 Quattro179,816
Check engine light on running rough. Smells hot. Smog code comes up when checked on computer.
I bought the car used in 2007 and it's been on ever since. We changed the sensor and it's still on. the cluster also has a problem with displaying and we got a 'used' one and still have the same problem. The electrical system must be messed up as the car alarm would go off for no reason. It's ok now. The engine is terrific and handling is great, it loves the road even in 2014 with 144,000 mi on it.
2004 Audi A4 Quattro122,000
Check engine light has come on. P0431 warm up
Check engine light came on, dealer says its the Catalytic Converter on the left side. Wants $2400 to fix. 2003 Audo Quattro 3.0
Engine light stays on. Catalytic converter fault.
Check engine light was loading due to faulty catalytic converter
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