Q: In my vehicle, the check engine light comes on and then goes off and it is now back on. I had a test done at local auto-parts store that showed a code of PO138. They told me this indicates a ...

A closed loop control system for regulation of engine air-fuel ratio at the stoichiometric value is required for effective operation of a three-way catalytic converter. System performance depends ...

April is Car Care Awareness Month — and also National Canine Fitness Month, International Guitar Month and National Soft Pretzel Month, among many others — and the folks at CarMD are back with their ...

I had a test done at local auto-parts store that showed a code of PO138. They told me this indicates a problem with the oxygen sensor. I replaced the oxygen sensor and the light never went out. I ...