FI6929
A09074
A
B
B+
Power Transistor
Platinum Hot Wire
(Heater)
Output
Voltage
Temperature
Sensor
Platinum Hot Wire (Heater)
Temperature Sensor
A94508
--
DIAGNOSTICS
ECD SYSTEM (1ND--TV)
05--55
COROLLA Supplement (RM1129E)
DTC
P0100
MASS OR VOLUME AIR FLOW CIRCUIT
CIRCUIT DESCRIPTION
The Mass Air Flow (MAF) 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 provides 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 incom-
ing 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 pro-
portional to the flow of the air passing 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, and
the power transistor is controlled so that the potential of A and B remains equal to maintain the predeter-
mined temperature.
HINT:
When the mass air flow meter output is outside the normal range, the ECM determines this as a malfunction.
DTC No.
DTC Detection Condition
Trouble Area
P0100
Condition (a) or (b) continues for 2.0 seconds or more:
(a) VG less than 0.14 V
(b) VG more than 4.8 V
(The MIL is illuminated as well as a DTC being set immediately
malfunction is detected)
S
Open or short in mass air flow meter circuit
S
Mass air flow meter
S
Contamination in mass air flow meter
S
ECM
HINT:
DTC P0100 is set while idling for 10 seconds or more after the engine was revved up to 3,000 rpm.
05MRO--01
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TOYOTA COROLLA REPAIR MANUAL SUPP 1129E