I bought a used F150. It was raining when I bought it and for a few days after. After everything dried out, it started throwing a couple of check engine lights related to the upstream O2 sensor and the turbo charger. I was going to replace the O2 sensor. It was raining again when I got around to it and by the time I got to my buddies garage, the check engine lights were gone again. A couple of days later, after things dried out, they are back. Any ideas where to look?

 

Welcome.

Perhaps list the info about your truck. Year, model, motor, etc.

 

HINT/TIP: Put your -complete- vehicle information (year, model, cab, trim, engine, wheelbase, _x4 drive, mileage, modifications, etc., etc.) in your signature -OR- provide it in your posting(s).
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You need to scan the PCM for active, stored or pending trouble codes.
Its also a remote possibility that your CEL light bulb or LED has an intermittent problem.

As the other said, post your vehicle info, we're not all mind readers.

 

Great. There have been several million made. Which one did you buy? Put ALL its details into your signature as this caption explains:

(phone app link)