Hi All!
I am new to this site and new to owning an Audi. I recently bought a 1998 A4 Quattro 2.8 that needed some TLC. I have began repairing some issues, but have hit a brick wall on one issue. My car is throwing oxygen sensor codes. The kid I bought it from put a Remus exhaust on it and replaced the Oxygen sensors, but when he put the sensors in he got universals and just twisted the wires together and taped them. I got around to looking underneath and the one sensor had rubbed up against the heat shield, causing the one white wire to rub through. I have replaced that sensor and the other one. They are still not reading. I have a scan tool that shows the fuel trim and it is not functioning. Could the bare wire of shorted the computer out? Also, if I used soldier-less connectors, will they still transfer heat and signal? Any ideas of how to fix this issue would be appreciated. It's driving me crazy! Thank you very much!

 

Kid might have fried the ECU with his wiring. You really need a VAG-COM to sort this out...unless you like throwing expensive parts at your car. Go to Meausuring Blocks 030-049 to read what's going on.

 

sometimes a bad coolant temp sensor can cause an 02 sensor code, it's only a $20 part

 

Welcome to AF! For your excellent username choice, I award you 1000 internets

As for the O2 sensors, were their any un-used wires either from the sensor side or the wiring harness side? When you replaced the replacements, did you use universal sensors again? Exactly which O2 sensor codes are being thrown? Did the Remus exhaust retain the catalytic converters?

 

Thanks for the replies!
Hiwords I will replace the coolant temp sensor to see what happens.

CCA4 there were no unused wires, unfortunately I had to use universals again because the previous owner cut the factory harness from the car. I am not sure off the top of my head what the codes are, I will get them and post them. The exhaust did retain the cats, but I think he may have hollowed them out. It does sound good, but it's more important to me that the car runs right and can pass my states emissions test. If you have any other suggestions let me know. Thanks again!

 

Ahhh see, that's why I asked!

If he hollowed out the cats, it's likely not the O2 sensors that are the problem, they're just doing their job. They think your cats are borked because the previous owner hollowed them out. Where are you located? If you don't have emissions inspection, you might be able to get away with running spacers on the rear O2 sensors so they don't throw codes. If you DO have to pass smog or emissions, you'll need to have some new cats welded into the exhaust.