Lexus SC300 / Lexus SC400. Manual — part 882
WIRING DIAGRAM
–
ENGINE TROUBLESHOOTING
Circuit Inspection
TR–107
NG
OK
OK
NG
OK
NG
INSPECTION PROCEDURE
1
Check voltage between terminal EGR of ECM connector and body ground.
C
OK
P
1.
Connect the Check Harness A. (See page
).
2.
Warm up engine to normal operating temperature.
Measure voltage between terminal EGR of engine (&
ECT) ECU connector and body ground.
Voltage:
Go to step
.
2
Check resistance between terminals of VSV for EGR.
C
OK
P
).
Measure resistance between terminals of VSV for EGR.
Resistance:
38.5 – 44.5
at 20
C (68
F)
Replace VSV for EGR.
3
Check for open and short in harness and connector between EFI main relay and VSV for EGR,
VSV for EGR and engine (& ECT) ECU. (See page
)
Repair or replace harness or connector.
Check and replace engine (& ECT) ECU.
TR–108
–
ENGINE TROUBLESHOOTING
Circuit Inspection
OK
NG
OK
NG
OK
NG
4
Check EGR system (See page
Repair EGR system.
5
Check resistance of EGR gas temp. sensor.
C
OK
P
Remove EGR gas temp. sensor.
Measure resistance between terminals of EGR gas
temp. sensor connector.
Resistance:
69 – 89 k
at 50
C (122
F)
12 – 15 k
at 100
C (212
F)
2 – 4 k
at 150
C (302
F)
Replace EGR gas temp. sensor.
6
Check for open in harness and connector between EGR gas temp. sensor and engine (& ECT)
ECU. (See page
Repair or replace harness or connector.
Check and replace engine (& ECT) ECU.
–
ENGINE TROUBLESHOOTING
Circuit Inspection
TR–109
Diag. Code 71
EGR System Malfunction (Only for USA
spec.)
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 lift amount of the EGR valve is controlled by a step motor operated by the ECU. The ECU operates the motor
only a preprogrammed amount in response to the engine operating conditions (engine rpm, intake air volume
to adjust the EGR volume to the target valve.)
Under the following conditions, EGR is cut to maintain driveability.
•
Coolant temp. below 535C (127.45F)
•
During deceleration (throttle valve
closed)
•
Light engine load (amount of intake air
very small)
•
Engine speed over 4,000 rpm
•
Engine idling
•
Neutral start switch on
Code No.
Diagnostic Code Detecting Condition
Trouble Area
(1) Open or short in EGR step motor circuit for 1 sec.
or more.
Open or short in EGR step motor circuit
ECU
71
(2) EGR gas temp. is 65
°
C (149
°
F) or below for
1 ~ 4 min. under conditions (a) and(b).
(2 trip detection logic)*
(a) Coolant temp.: 65
°
C (149
°
F) or more.
(b) EGR operation possible (EX. ECT in 3rd speed,
A/C ON, 60 mph (96 km/h), Flat road).
Open in EGR gas temp. sensor circuit
ECU
*: See page
TR–108
–
ENGINE TROUBLESHOOTING
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