Toyota Camry Manual page 1249

DI–222
CIRCUIT INSPECTION
DTC P0100
CIRCUIT DESCRIPTION
The mass air flow meter uses a platinum hot wire. The hot wire air flow meter consists of a platinum hot wire,
thermistor and a control circuit installed in a plastic housing. The hot wire air flow meter works on the principle
that the hot wire and thermistor located in the intake air bypass of the housing detect any changes in the
intake air temperature.
The hot wire is maintained at the set temperature by controlling the current flow through the hot wire. This
current flow is then measured as the output voltage of the mass air flow meter.
The circuit is constructed so that the platinum hot wire and thermistor provide a bridge circuit, with the power
transistor controlled so that the potential of A and B remains equal to maintain the set temperature.
Thermistor
A
FI6929
S05741
DTC No.
Open or short in mass air flow meter circuit with more than 3
P0100
sec. engine speed 4,000 rpm or less
If the ECM detects DTC 0100 it operates the fail–safe function, keeping the ignition timing and injection vol-
ume constant and making it possible to drive the vehicle.
HINT:
After confirming DTC P0100, use the OBD II scan tool or TOYOTA hand–held tester to confirm the mass
air flow ratio from "CURRENT DATA".
Mass Air Flow Value (gm/sec.)
0.0
271.0 or more
DIAGNOSTICS
Mass Air Flow Circuit Malfunction
B+
Power Transistor
Platinum Hot wire
B
Output
Voltage
DTC Detecting Condition
– ENGINE (1MZ–FE)
D Open or short in mass air flow meter circuit
D Mass air flow meter
D ECM
D Mass air flow meter power source circuit open
D VG circuit open or short
D E2G circuit open
Author :
Platinum Hot
Thermistor
Wire
Trouble Area
Malfunction
Date :
DI07F–06
A00435
457