Toyota ZZT230 series Repair Manual page 234

CIRCUIT INSPECTION
DTC
CIRCUIT DESCRIPTION
The mass air flow meter uses a platinum hot wire. The hot wire airflow meter consists of a platinum hot wire,
thermlstor and a control circuit installed in a plastic housing. The hot wire air flow meter
that the hot wire and thermistor located In the intake air bypass of the housing detect any changes in the
intake air temp.
flow is then measured as the output voltage of the air flow meter. The hot wire is maintained at the set temp. by controlling the current flow through the hot
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.
Open Of short in mass air flow meter circuit with more than 3
PO!OO
sec. engine speed 4,000 rpm
volume If the ECM detects DTC
constant and making
HINT:
flow ratio from "CURRENT DATA"
After confirming DTC
Mass Air Flow Value
)
DIAGNOSTICS
P01 00
Mass Air Flow Circuit Malfunction
Power Transister
DTC
Detecting
CorKition
or less
I t it operates the fail-safe function, keeping the ignition timing and injection
"P0100"
possible to drive the vehicle.
P0100 use the OBD
(gmlsec.)
0.0
271.0 or more
ENGINE
Output
Voltage
•Open or short in mass air flow meter circuit
• Mass air flow meter
•ECM
I I
scan tool or TOYOTA hand-held tester to confirm the mass air
or
• Mass air flow meter power source cirCl.lit open
• va circuit open short
• E2G
circuit
on the principle
works
This current
wire.
Trouble Area
Malfunction
Dl-23
A06106