my buddy gets the check engine light for his secondary o2 sensor on deceleration. Doesn't matter what gear or anything, as soon as the car decelerates bam cel comes on. just replaced the o2 sensors not that long ago. any ideas you got would help

Guess i should also mention it's a b16a in a 4dr civic.

 

Still Pre-OBD 1 wire? Or OBD2?

 

could be a bad cat

 

it's obd0

 

Stock exhaust manifold? Tee it into the other one.

 

okay we'll try that. it's a hollowed out cat, but happens with a brand new cat and won't pass emissions either way.