Toyota Celica 2005 Repair Manual page 565

DI−366
DTC P0100
DTC P0102
DTC P0103
CIRCUIT DESCRIPTION
The MAF (Mass Air Flow) 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 incom-
ing air cools the wire and an internal thermistor, changing 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 airflow through the sensor and the ECM interprets this voltage as the intake air amount.
The circuit is constructed so that the platinum hot wire and the 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 temper-
ature.
Temperature Sensor
FI6929
A09074
DTC No.
When the mass air flow meter circuit has an open or short for
P0100
more than 3 seconds under the 4,000 rpm engine speed
When the mass air flow meter circuit has an open for more
P0102
than 3 seconds under the 4,000 rpm engine speed
When the mass air flow meter circuit has a short for more than
P0103
3 seconds under the 4,000 rpm engine speed
HINT:
After confirming DTC P0100, P0102 or P0103, confirm the mass air flow ratio in the "DIAGNOSIS / EN-
HANCED OBD II / DATA LIST / ALL" using the hand−held tester or the OBD II scan tool.
2005 CELICA (RM1131U)
DIAGNOSTICS
Mass or Volume Air Flow Circuit
Mass or Volume Air Flow Circuit Low Input
Mass or Volume Air Flow Circuit High Input
B+
Power Transistor
Platinum Hot Wire
(Heater)
B
A Output
Voltage
DTC Detection Condition
− ENGINE (2ZZ−GE)
Temperature
Sensor
Platinum Hot Wire (Heater)
S Open or short in mass air flow meter circuit
S Mass air flow meter
S ECM
564
Trouble Area
DI09B−27
A09707