202 Corolla P0171 - Toyota Nation Forum : Toyota Car and Truck Forums

garymarkham · 05-10-2011, 09:58 AM

I went to Autozone to get the computor to do a scan to see why my CIL is on and I got a P0171 O2 sesor bank 1.

I have read where the most likely problem may be with my MAS, and I may just need to clean. I also read where if this is not the problem it may be a bad O2 senso.

The fuel millage has dropped by 2-3 MPG.

Any advise?

Thanks

fishexpo101 · 05-10-2011, 03:04 PM

First thing I'd do is clean the MAF sensor carefully with MAF specific cleaner (to be safe). Reset the CEL and see if it comes back. Probably would be a good idea to clean the throttlebody out as well - same with the PCV valve. Pull the plugs out and read the ends - note any significant differences between the plugs. Make sure the air filter is in good shape and there are no cracks/damage to the airbox (make sure there is a possible seal with the clips engaged) and hose running to the throttlebody doesn't have any rips/cracks in the ribbed tubing.