P22417
Exhaust
Gas
Intake Air
Chamber
EGR
Valve
VSV
EGR
Vacuum
Modulator
ECM
Throttle
valve
P22426
BR
From Battery
R/B No.2
R
−
Y
2 2
2
2
2
2
Y
−
R
E
F
I Main
Y
−
R
1
2
4
3
R
EA2
EZ1
EB1
2
7
VSV for EGR
2
1
Y
Y
L
−
W
EZ1
4
EGR Gas Temp.
Sensor
2
1
G
−
Y
BR
−
B
E7
E4
E4
E5
3
22
19
9
THG
E1
EGR
E2
5V
MRLY
ECM
R
EB
EFI
1
Relay
B+
E01
−
DIAGNOSTICS
ENGINE
DI
−
69
1996 LAND CRUISER (RM451U)
DTC
P0401
Exhaust Gas Recirculation Flow Insufficient
Detected
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.
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.
S
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.
DTC No.
DTC Detecting Condition
Trouble Area
P0401
After the engine is warmed up and run at 80 km/h (50 mph)
for 3 to 5 minutes, the EGR gas temperature sensor value
does not exceed 38
°
C (100.4
°F) above the ambient air tem-
perature. (2 trip detection logic)
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
WIRING DIAGRAM
DI5PK
−
02
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Version 1.00 - 12/21/2010