Exhaust Gas Recirculation Flow Insufficient Detected - Toyota T100 1996 Service Manual

DI−72
DTC P0401
CIRCUIT DESCRIPTION
The EGR system recirculates exhaust gas, which is controlled to the proper quantity to suit the driving condi-
tions, into the intake air mixture to slow down combustion, reduce the combustion temp. and reduce NOx
emissions. The amount of EGR is regulated by the EGR vacuum modulator according to the engine load.
Throttle Body
Throttle
Valve
ECM
EGR Vacuum Modulator
DTC No.
After engine is warmed up and run at 80 km/h (50 mph)
for 3 to 5 min., EGR gas temp. sensor value does not exceed
P0401
35°C (95°F) above ambient air temp.
(2 trip detection logic)
WIRING DIAGRAM
From Battery
From
IG Switch
3
1A
J/B
No.1
17
1C
4
B−Y
EA1
1996 TOYOTA T100 (RM449U)
DIAGNOSTICS
Exhaust Gas Recirculation Flow Insufficient
Detected
Check
Valve
(for A/T)
VSV EGR
Valve
P19893
DTC Detecting Condition
B−W
2 2
EFI Relay
5
2
EFI
5
2
1
R/B No.2
− ENGINE (3RZ−FE)
If even one of the following conditions is fulfilled, the VSV is
turned ON by a signal from the ECM.
This results in atmospheric air acting on the EGR valve, closing
the EGR valve and shutting off the exhaust gas (EGR cut−off).
Under the following conditions, EGR is cut to maintain driveabil-
ity:
Before the engine is warmed up
S
During deceleration (throttle valve closed)
S
Light engine load (amount of intake air very small)
S
Engine racing
S
S EGR valve stuck closed
S Short in VSV circuit for EGR
S Open in EGR gas temp. sensor circuit
S EGR hose disconnected
S ECM
9
W−R W−R
2
EA1
3
2
2
EGR Gas
EA
Temp. Sensor
Trouble Area
VSV for EGR
6 22
9
P
W−R
E7 E7
IE1
2 1
3
2 G−W
E6 E6
9
1
BR−B
E6 E6
(M/T)(A/T)
DI0TU−03
ECM
EGR
E01
5 V
14
THG
9
E2
E1
P19921