Circuit Description

Mass Air Flow (MAF) sensor measures amount of air which passes through it into engine during a given time. PCM uses MAF information to monitor engine operating conditions for fuel delivery calculations. A large quantity of air entering the engine indicates an acceleration or high load situation, while a small quantity of air indicates deceleration or idle. MAF sensor produces a frequency signal which can be monitored using a scan tool. Frequency will vary within about 4-7 grams/sec. at idle to about 25-40 grams/sec. at maximum engine load. DTC P0101 will be set if signal from MAF sensor does not match a predicted value based on throttle position and engine RPM.

When DTC sets, PCM illuminates MIL on second trip after fault was detected. PCM calculates an air flow value based on idle air control valve and throttle position sensor positions, RPM and barometric pressure. PCM will store conditions present when DTC was set as freeze frame data in the FAILURE RECORDS data.

PCM will turn MIL off on third consecutive trip cycle during which diagnostic runs and fault is no longer recognized. A history DTC P0101 will clear after 40 consecutive trip cycles during which diagnostic runs and fault is no longer recognized. DTC can be cleared with scan tool, or by disconnecting battery voltage feed to PCM.