DTC P0102 Mass or Volume Air Flow Circuit Low Input; DTC P0103 Mass or Volume Air Flow Circuit High Input: Description

WARNING: This page is about a different variant/trim than selected.

The mass air flow meter is a sensor that measures the amount of air flowing through the throttle valve. The ECM uses this information to determine the fuel injection time and to provide the appropriate air-fuel ratio.

Inside the mass air flow meter, there is a heated platinum wire which is exposed to the flow of intake air. By applying a specific electrical current to the wire, the ECM heats it to a given temperature. The flow of incoming air cools both the wire and an internal thermistor, affecting their resistance. To maintain a constant current value, the ECM varies the voltage applied to the wire and internal thermistor. The voltage level is proportional to the airflow through the sensor, and the ECM uses it to calculate the intake air volume.

The circuit is constructed so that the platinum hot wire and the temperature sensor create a bridge circuit, and the power transistor is controlled so that the potentials of A and B remain equal to maintain the predetermined temperature.

HINT:

When any of these DTCs is stored, the ECM enters fail-safe mode. During fail-safe mode, the ignition timing is calculated by the ECM, according to the engine speed and throttle valve position. Fail-safe mode continues until a pass condition is detected.

Fig 1: Mass Air Flow Meter Sensor - Circuit Diagram

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

DTC DETECTION CONDITION CHART

DTC No.	DTC Detection Condition	Trouble Area
P0102	The mass air flow meter voltage is less than 0.2 V for 3 seconds. (1 trip detection logic: Engine speed is less than 4000 rpm) (2 trip detection logic: Engine speed is 4000 rpm or more)	Open or short in mass air flow meter circuit Mass air flow meter ECM
P0103	The mass air flow meter voltage is more than 4.9 V for 3 seconds. (1 trip detection logic: Engine speed is less than 4000 rpm) (2 trip detection logic: Engine speed is 4000 rpm or more)	Open or short in mass air flow meter circuit Mass air flow meter ECM

HINT:

When any of these DTCs are output, check the air-flow rate using the Techstream. Enter the following menus: Powertrain/Engine/Data List/All Data/MAF.

MASS AIR FLOW RATE CHART

Mass Air Flow Rate (gm/sec)	Condition	Malfunction
Approximately 0.0	Engine not running 30 seconds after ignition switch turned to ON	Open in mass air flow meter power source circuit Open or short in VG circuit
0.71 or more	Engine not running 30 seconds after ignition switch turned to ON	Open in E2G circuit

NOTE:

Perform the inspection with the vehicle indoors and on a level surface.
Perform the inspection of the mass air flow meter while it is installed to the air cleaner case (installed to the vehicle).
During the test, do not use an exhaust air duct on the exhaust tail pipe assembly.