A18694
ECM
Throttle Body
Throttle
Valve
EGR Vacuum Modulator
VSV EGR
Valve
A18633
A1
ECM
V3
VSV for EGR
2
R–B
EGR
E01
5 V
E1
18
1
L–B
19
E2
1
13
7
From
Terminal 3 of EFI Relay
(See page DI–206)
E1
EGR Gas
Temp. Sensor
P–L
5
J/B No. 3
THG
E7
E7
E7
2
W–R
W–R
W–R
W–R
IK2
IF1
3E
3E
1
3
–
DIAGNOSTICS
ENGINE (2RZ–FE, 3RZ–FE)
DI–101
363
Author:
Date:
2003 TOYOTA TACOMA (RM1002U)
DTC
P0401
Exhaust Gas Recirculation Flow Insufficient
Detected (Only for 3RZ–FE)
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 temperature 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.
Before the engine is warmed up.
During deceleration (throttle valve closed).
Light engine load (amount of intake air very small).
Engine racing.
DTC No.
DTC Detection Condition
Trouble Area
Open in EGR gas temp. sensor circuit
EGR gas temp sensor
After engine is warmed up and run at 80 km/h (50 mph) for 3 to
.
Vacuum or EGR hose disconnected
Open or short in VSV circuit for EGR
P0401
5 minutes, small difference between value of EGR gas temp.
VSV for EGR
EGR
t
sensor and ambient air temp. (2 trip detection logic)
sysem
EGR vacuum modulator
EGR valve stuck closed
ECM
WIRING DIAGRAM
DI12Y–16
S06906
Vehicle Speed
70 – 90 km/h
(43 – 56 mph)
Idling
IG SW OFF (a)
(b)
(c)
(d)
(e)
(f)
Warm up
3 – 5 min.
2 min.
Time
3 – 5 min.
2 min.
DI–102
–
DIAGNOSTICS
ENGINE (2RZ–FE, 3RZ–FE)
364
Author:
Date:
2003 TOYOTA TACOMA (RM1002U)
SYSTEM CHECK DRIVING PATTERN
(a)
Connect the hand–he