Toyota Repair: 2000 Corolla P0171 OBDII Error Code, p0171 system too lean bank 1, maf sensor

Question
Hi Mike,

The "check engine" light came on in my wifes 2000 Corolla recently.  When hooked up to a scanner the code error reads P0171 (System Too Lean Bank 1).  I've read dozens of forums on different websites and most seem to circulate around cleaning the MAF (however that is done) or changing O2 sensors.  Beyond the P0171 code the car seems to hesitate for a very brief moment when accelerating from a complete stop.  Could this be related?

Based on your expertise and experience, what would you do and in what order?  Any resources you can provide that have "how-to's" would be appreciated.  I'm ambitous and would like to work on the car myself but am fairly inexperienced! :-)

Thanks in advance!!

~ Chris

Answer
check the freeze frame data with the scanner. If the fuel trim is high teens or in the 20s then its the MAF that the problem. If fuel trim is normal, 2-5 then its the O2 sensor.

MAF-
Buy "Electrickleen" at the parts store.
Remove the MAF sensor, WHILE COLD, and blast the wire inside with cleaner.
The "hotwire" gets gummed up and changes the resistance of the wire so you get a bad input to the ecu and it trys to lean out for a rich condition that doesnt exsist.When it cant adjust anymore it trips the po171 code.



Mike