So I take my 03 Sebring to my trusted mech with check engine light brightly shining. OBD code sez catalytic converter. He installs a new converter and erases the code. Two days later check engine light returns. OBD pulls the same code. He checks the installation and erases the code again. Less than a day later, check engine light again. No other codes, can't find anything else wrong. Has this happened to anyone else? Any possible theories?

 

Also gives P1684, but I just read up on that, not worried.

 

Did he replace the O2 sensors? The computer takes a reading from the upstream and the downstream O2 sensors to determine the health of the cat converter. It compares those readings to determine how well the converter is working. If one of the sensors is not right, it could cause the computer to think that there is something wrong with the converter. I would change both the upstream and downstream sensor since they work in pairs. While he's under there, have him also make sure there's no leakage around the converter. That can also screw up readings. People on the forum here have reported problems with Bosch sensors. Probably best to avoid those.

 

Yes, he replaced both O2 sensors, but I don't know what brand he used. And he used all new gaskets when he replaced the cat.