Toyota 1996 LAND CRUISER User Manual page 456

DI−20
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 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.
B+
Thermistor
A
FI6929 P22263
DTC No.
Open or short in mass air flow meter circuit with engine
P0100
speed 4,000 rpm or less.
If the ECM detects DTC" P0100" it operates the fail safe function, keeping the ignition timing and injection
volume constant and marking 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.)
Approx. 0
439.0 or more
1996 LAND CRUISER (RM451U)
Brought to you by BirfMark
DIAGNOSTICS
Mass Air Flow Circuit Malfunction
Power Transistor
Platinum Hot Wire
B
Output Voltage
Thermistor
DTC Detecting Condition
S Mass air flow meter power source open
S VG circuit open or short
S E21 circuit open
Brought to you by BirfMark
Version 1.00 - 12/21/2010
− ENGINE
S Open or short in mass air flow meter circuit
S Mass air flow meter
S ECM
Malfunction
DI5OZ−02
Platinum Hot Wire
Trouble Area
A00152