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 ...

I live in New Jersey, one of the states that mandates inspection for all vehicles newer than 1995. My daily driver, a Jeep Cherokee, happens to be a 1996 model year with an OBD-II sensor, meaning I ...

Modern vehicles are pretty complicated pieces of tech. Apart from emissions and other vital functions, the engine control system relies heavily on several sensors to regulate performance. That is ...

How many oxygen sensors does a typical car have, and what factors determine this number? Additionally, how do their placements affect engine performance and emissions control? Thomas Hello Thomas, the ...