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

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 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 these components in the mass air flow meter 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 provide 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 are set, 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: Identifying Temperature Sensor With Platinum Hot Wire (Heater)

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

HINT

When any of these DTCs are set, check the air-flow rate by entering the following menus Powertrain / Engine / Data List / MAF