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DTC P0101 Mass Air Flow Circuit Range / Performance Problem: Description

The Mass Air Flow (MAF) meter measures the amount of air flowing through the throttle valve. The ECM uses this information to determine the fuel injection time and provide a proper air-fuel ratio. Inside the MAF meter, there is a heated platinum wire exposed to the flow of intake air.

By applying a specific current to the wire, the ECM heats this wire to a given temperature. The flow of incoming air cools the wire and an internal thermistor, affecting their resistance. To maintain a constant current value, the ECM varies the voltage applied to these components in the MAF meter. The voltage level is proportional to the air flow through the sensor. The ECM interprets this voltage as the intake air amount.

The circuit is constructed so that the platinum hot wire and temperature sensor provide a bridge circuit, with the power transistor controlled so that the potential of A and B remains equal to maintain the set temperature.

Fig 1: Identifying Mass Air Flow Circuit Range
G04026827Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
DIAGNOSTIC TROUBLE CODE CHART

DTC No. DTC Detection Condition Trouble Area
P0101  Case 1
MAF meter voltage is higher than MAF meter voltage based on throttle position when the following conditions are met (2 trip detection logic):
  1. Engine Coolant Temperature is 70°C (158°F) or more
  2. Engine speed is less than 2,000 RPM

Case 2
MAF meter voltage is lower than MAF meter voltage based on throttle position when the following conditions are met (2 trip detection logic):
  1. Fuel cut is not executing
  2. Engine speed is more than 300 RPM
>MAF meter