Toyota Corolla (E120) 2002–2008 Repair Manual / Diagnostics / Sfi system / Mass or volume air flow circuit range/performance problem / Circuit description

Toyota Corolla (E120): Circuit description

Refer to dtcs p0100

Dtc no.	Dtc detection condition	Trouble area
P0101	After engine is warmed up, conditions (a) to (d) continue for more than 10 seconds (2 trip detection logic):  engine speed less than 900 rpm  throttle valve fully closed  mass air flow sensor output greater than 2.2 V  engine coolant temperature higher than 70 c (158 °F)	Mass air flow sensor
	Conditions (a) and (b) continue for more than 6 seconds: (2 trip detection logic)  vta greater than 0.1 V  mass air flow sensor output less than 0.4 V

Monitor description

The maf (mass air flow) sensor helps the ecm calculates the amount of air flowing through the throttle valve. The ecm uses this information to determine the fuel injection time and provides a proper air–fuel ratio.

Inside the maf sensor, 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 thermister, changing their resistance. To maintain a constant current value, the ecm varies the voltage applied to these components in the maf sensor. The voltage level is proportional to the air flow through the sensor and the ecm interprets this voltage as the intake air amount. If there is a defect in the sensor or an open or short circuit, the voltage level will deviate outside the normal operating range. The ecm interprets this deviation as a defect in the maf sensor and sets a dtc.

Example: if the voltage is more than 2.2 V at idle, or less than 0.4 V at idle off, the ecm interprets this as a defect in the maf sensor and sets a dtc.

Monitor strategy

Typical enabling conditions

Typical malfunction thresholds

Wiring diagram

Refer to dtc p0100