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 have a 99 Mustang. About a year or so ago, my check engine light (hereby known as the CEL) went on. I took it to my local shop, who charged my $75 and said they fixed it. 2 days later, it comes back ...

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 ...