DI1IB--01
FI6929 P26036
A02312
B+
Power Transistor
Platinum Hot Wire
Output Voltage
Thermistor
Platinum Hot Wire
Thermistor
A
B
DI--94
--
DIAGNOSTICS
ENGINE (2RZ--FE, 3RZ--FE)
CIRCUIT INSPECTION
DTC P0100/31 Air Flow Circuit Malfunction
CIRCUIT DESCRIPTION
The air flow meter uses a platinum hot wire. The hot wire air flow meter consists of a platinum hot wire, therm-
istor 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 temp.
The hot wire is maintained at the set temp. 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 temp.
DTC No.
DTC Detecting Condition
Trouble Area
P0100/31
Open or short in air flow meter circuit for 3 sec. engine speed
S
Open or short in air flow meter circuit
Ai fl
t
P0100/31
Open or short in air flow meter circuit for 3 sec. engine speed
or more 3,000 rpm
S
Air flow meter
S
Engine ECU
If the engine ECU detects DTC ”P0100/31” 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 ”P0100/31” use the hand--held tester to confirm the air flow ratio from ”CURRENT
DATA”.
Mass Air Flow Value (gm/sec.)
Malfunction
Approx. 0
S
Air flow meter power source circuit open
S
VG circuit open or short
271.0 or more
S
E2G circuit open
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3RZ-F,3RZ-FE