So I had my catalytic converters replaced on my 96 A4q(direct fir OEM, not universal) by a good muffler shop in the area. They were a bit concerned about the O2 sensors coming out OK, but they did, and reinstalled fine.

All was fine until the following day when the check engine light came on. Took it to the local auto store and 3 of the 4 O2 sensors coded up, but we cleared them, and it was good for another day, same sensors scanned, cleared the codes, they were good until my wife drove it 200 miles on the freeway and stopped at a stop light. The light always comes on when the car is idling, the sensors are plugged in correctly and nice and tight.

Any thoughts? Does it need to go to a dealer for a complete computer clear or something? I would find it odd that 3 sensors would be bad just by moving them into a new pipe.

Help!?!?!?

 

If they're original, it wouldn't surprise me a bit. They're probably all gunked up and are pissed that you disturbed them.

 

Took it back to the muffler shop that installed the cats/pipes. There was one loose 02 sensor, go figure, the only one that didn't code out. It's been driven about 20 miles and no code. Realism says it will come back but You never know!