Check engine light with cold weather starts

The check-engine light on my 2006 Toyota Corolla came on a couple of weeks ago after I started the car on a 7-degree F morning. Code was P-0171. Mechanic cleaned the MAF and the light went off. Light stayed off 'til I started the car on another 7-degree F morning. Mechanic said that the MAF didn’t look dirty, and the readings didn’t change after cleaning. No vacuum leaks. O2 sensors responding normally. Any thoughts on what’s going on? I travel a lot in this car, so I don’t want to damage the car by ignoring the check-engine light. Suggestions?


“No vacuum leaks.”

How sure are you?

Did you use an evap/smoke machine to verify this?

Not all vacuum leaks can be heard . . . and not all vacuum leaks can be found with carb cleaner

Anyways, moving on, check this out . . .

This other bulletin seems to better match your cold weather symptoms

By the way, I understand you say you don’t have vacuum leaks, but that second bulletin I posted seems to exactly describe your complaint

Please let us know what finally fixes the car