Which of 2 sensors top or side of airflow box on 2000 Toyota Avalon should be replaced for code p0171?

Answer 1

there is only one sensor on the airbox. its flat on top with 2 Phillips screws holding it in place and a 5 or 6 wire plug. the other thing has vacuum hoses to it and is a switching valve. ask for the mass airflow sensor when you go to buy the part. If you still cant identify it, call the dealer, ask for the price and part number for a MAF sensor, then match that number to the one on the sensor itself.

the biggest problem I have with trying to fix a code P0171 with a MAF sensor is you could pay the $90.00 or whatever and have it not fix the problem. make sure its reading too low at idle before replacing it. check it on the data list of a scan tool, it should be between 2.5 and 3.5 gm/sec. if its lower, make sure the air snorkel between the airbox and throttle body is secure and not leaking. if that's ok replace the sensor. if its in range AFR bank 1 needs to be compared to bank 2. if its reading a higher voltage or isn't as lively at say 2500 rpm replace AFR bank 1. (its the first sensor in the exhaust by the firewall NOT THE ONE BY THE RADIATOR!