Cat or O2 sensors bad?
I have a 2009 Traverse with 140k on the odometer.
It throws 0420 and randomly 0300 codes.
Check engine light came and I checked for codes and deleted them. 2 Days nothing. Then we started a 1000 mile roadtrip and there was everything ok.
Yesterday I drove hom from work and a short time after start (2 miles approx) Check engine light appears again. Deleted the failure code and until now nothing happend.
Does it make sense to change the O2 sensors or is one of the catalytic converters going bad? Need your experience.
Many thanks from Germany