I have a 2001 A4 90000 miles on it. The Check Engine Light is always on. I took it to two different audi dealerships and they changes the O2 sensor, and the air flow sensor, but the light keeps returning back on.

Any ideas ?

Thanks in advance,

Mark

 

what are the codes you are getting, go to autozone or a local parts store get your car scanned and let people know what the code is, like p1041 p1613

that will make it easier for people to help

 

is it running rough at all?? especially on startup when it's cold out??
I had a coolant temperature sensor cause that. I also had sensors up and downstream of CATs give bad readings, and they tried to tell me that i needed new CATs, but it turned out it just needed a computer re-program, there was a technical service buliten out on it, but mine is a 2000

 

Hi Guys,
Thanks for replying, The error is P0411 (Secondary Air injection system - Incorrect flow)

The audi dealer ship replaced 2 sensors : Oxygen sensor, AirFlow sensor.

The car starts fine, and when i am driving it feels like the car lost 30 hp.

Thanks in advance
Mark

 

The reason it feels like it has 30 hp less is because it prolly is at least 30 HP less, if not even more than that. When your cel comes on the ecu goes into limp mode and will open the wastegate at 4psi instead of 10 psi to avoid detonation if its a missfire problem. One tip I have been told in the past with the B5 1.8t's is to take off the maf sensor and clean the inside of it very thouroghly with a little bit of electronic safe cleaner found at most retail stores that sell computers. The sensor is very sensitive to dirt and can cause a cel stating it is from another source in the fuel system. Give it a shot. You've already done everything else. It will take you prolly a half hour and $10 for the cleaner. Not to mention you may have to go back to the dealer and have the light shut off. Good Luck!!!!

 

Just wonderin what the MAF sensor is. what does that sound like and where is it located in the 1.8t's engine bay? thanks ive got this same code on my a4.

 

You dont need to resurect old threads to ask questions, either post a new thread or just use the search.

The MAF sensor measures how muchair is entering the intake/engine so the ECU can compensate for fuel/timing, etc. It doesnt sound like anything. Its located inside the airbox, your turbo inlet pipe is connected to it on the front.

 

P0411 error is for the secondary air flow, which is connected to the air box, but separate from the main intake. TheMAF sensor is located in the in the path of main intake, so how is the MAF sensor reading affecting secondary air when it is a different path? I have the same problem, and in search for a solution.

 

He meant MAF when he said he replaced the airflow sensor.
He has a problem with the secondary air injector .

 

I have the same problem. My mechanic told me that he still needs to check some fuses and parts of the electrical system because the Air injection system is not working at all, but just for curiosity, how much did the dealer charged you?