Tech Tips (by ALLDATA): Toyota Rav4 DTC P0171 fix
TECH TIPS (courtesy of ALLDATA)
Problem: The vehicle came from another shop. They had installed a new Mass Airflow (MAF) sensor but the MIL/DTC would not clear.
Details: The technician pulled DTC P0171. The fuel trims verified that the fuel system was lean. The technician introduced propane into the intake manifold. The Oxygen sensors and fuel trims responded correctly.
Confirmed Repair: Since the fuel management system appeared to be working correctly, the technician decided to replace the aftermarket MAF sensor with an OEM (Denso) MAF sensor. He cleared the Keep Alive Memory and performed the appropriate dive cycle to insure the repair was complete. The MIL did not come back on. Problem solved by an OEM part.