Code P2196 MOT Failure /Pass

[Ray J Vee]

Hi everyone. I am looking for some advise please.
My 1.4 TFSI (8V) A3 Saloon with only 24000 miles failed the MOT as the emissions were far too high, Co 2.39% vol No engine management lights were showing on the the dash.

The tester allowed me to plug in my OBD2 reader and it displayed DTC code P2196 O2 Sensor signal stuck rich (bank1 sensor 1) .I erase the code and the car was re tested and the emission readings dropped significantly and were well under the MOT limits and the car passed.
Can anyone explain why this happened and what does erasing the code do. As the car is not showing any other symptoms (Exhaust smoke misfiring or poor fuel economy) I suspect the O2 sensor but cannot understand why clearing the DTC code made such a difference to the emissions.

Anyone any ideas ?
Thanks Ray

[Crasher]

When the ECU detects a problem it puts the car in limp mode, clearing the code puts it back to original, does the engine malfunction warning light come on with the ignition and go off after starting?

[DeBrun]

Hi, I don’t have a solution but can tell you the things I’ve tried that didn’t work. I also have a 1.4 tfsi A3 (sportback not saloon, CoD version of the engine, 64 plate, now 45k miles). Since approx 35k miles my check engine light has also been coming on every month or so with the P2196 error code.

I’ve replaced Bank 1 Sensor 1 twice (to rule out a faulty sensor) and have just replaced B1S2 closer to the Cat and this hasn’t fixed it either.

Same as your situation, seems to run absolutely fine, decent mpg etc but then when the error code comes back, I notice a slight drop in mpg. I clear the code, and I get 4-8wks of normal diving again before the error comes on again.

Sorry the above doesn’t help much but it might save you from forking out for a couple of sensors, which hasn’t helped my situation. Cheers

[Crasher]

What is the fault code number, the part numbers of the sensors you have replaced and the cars VIN?