1991 LEXUS SC400 check engine

OK
NG
Type I
NG
Type II
NG
OK
OKNG
INSPECTION PROCEDURE
1Check output condition of diag. code 51.
C
P(2) Connect terminals TE2 and E1 of TDCL.
(2) Turn ignition switch on.
(2) Crank the engine.
(2) Connect terminal TE1 and E1 of TDCL.
Check if diagnostic code ª51º is output when then shift
level is in the P and D shift positions.
Result:
Go to step 2.
Go to step 3.
Proceed to next circuit inspection shown on ma-
trix chart (See page TR±35).
2
Check for open in harness and connector between engine & ECT ECU and neutral \
start switch
(See page IN±27).
Check and replace engine & ECT ECU.
Repair or replace harness or connector.
3Check neutral start switch (See page AT±100).
Replace neutral start switch.
Check and replace engine & ECT ECU.
±
ENGINE TROUBLESHOOTING Circuit InspectionTR±123
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SERVICE HINTS FOR REFRIGERANT LEAK DETECTIONPage 2 of 3
B.Checking for leakage at the evaporator: The evaporator drain hose provides an
excellent access point to check for refrigerant leakage from the evapora\
tor. Be sure
to raise the vehicle on a lift so that the evaporator is as far as possi\
ble from any
petrochemical source that may be on the shop floor. When leak checking in this area,
turn the system off, pinch off the evaporator drain hose, and wait 10 to 15 minutes to
allow the refrigerant to accumulate in the evaporator case. When the s\
ystem is ready
to check, release the drain hose and hold the leak detector wand about 1\
/4 inch below
the drain opening (see diagram).
NOTE: Do not allow the leak detector tip to come in contact with water from th\
e evaporator.
C. Checking for leakage at front compressor seal:
Front compressor seal leaks are
probably the most difficult leaks to detect accurately. Special diagnostic procedures must be followed
for the best success. Make sure the system is fully charged. Operate the \
system with a pressure gauge
installed and assure that the system has correct system pressures. Shut off the engine. Begin the
leak check by placing the detector probe along the bottom half of the compr\
essor clutch. Move the wand
slowly across the bottom of the compressor clutch. Be careful not to expose t\
he detector wand tip to
any oil residue as this may cause a false leakage reading.
Evaporator
Drain Hose
Verify correct system pressure. Move dectector wand slowly across the
bottom half of the compressor clutch.
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15
ABBREVIATIONS
DISCONNECTION AND CONNECTION OF BOLT
TYPE CONNECTORS
For engine and ECT ECU in this vehicle, connectors are used
which require a bolt built into the connector to be screwed down to
securely connect the connector.
1. Disconnect the connectorAfter completely loosening the bolt, the two parts of the
connector can be separated.
NOTICE:
Do not pull the wire harness when disconnecting the
connector.
2. Connect the connector
NOTICE:
Before connecting the connector, always check that the
terminals are not bent or damaged.
(a) Match the guide section of the male connectorcorrectly with the female connector, then press them
together.
(b) Tighten the bolt. Make sure the connectors are completely connected,
by tightening the bolt until there is a clearance of less
than 1 mm (0.04 in.) between the bottom of male
connector and the end of female connector.
ABBREVIATIONS
The following abbreviations are used in this manual.
A/C = Air Conditioning O/D = Overdrive
ABS = Anti±Lock Brake System R/B = Relay Block
A/T = Automatic Transmission RH = Right±Hand
CB = Circuit Breaker SRS = Supplement Restraint System
COMB. = Combination SW = Switch
ECT = Electronic Controlled Transmission TDCL = Total Diagnostic Communication Link
ECU = Electronic Control Unit TEMP. = Temperature
EGR = Exhaust Gas Recirculation TRAC = Traction Control
FL = Fusible Link VSV = Vacuum Switching Valve
ISC = Idle Speed Control W/ = With
J/B = Junction Block W/O = Without
LH = Left-Hand
* The titles given inside the components are the names of the terminals (ter\
minal codes) and are not treatedas being abbreviations.
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221
1E
19 1E 14
1H
11 1H 7
IK1
16 IK1 17
2
L
LH
TURN
A
5A 16 B 17 B16
C
23
1 IK2
5 IK2
4
SEAT BELT
ABS
TRAC
TRAC OFF
A
19 A 7B15 B 5B1
W±B
LG±R W
V
LG±R
TO ABS AND
TRACTION ECU
(
IND )
TO ABS AND
TRACTION ECU
( WT ) G
W G±Y
G±B
G±B G±Y WG
R±W
FROM
A/T INDICATOR SW
OIL PRESSURE SW RH
Y±B
O2
COMBINATION METER C12 , C 1 3
,C14
ABC
I23
WW
TO TDCL (
TRC )
IK 2
9
Y±B
I22
L±Y
IO1
7
L±Y
I23
L
L±Y
TO ENGINE AND
ECT ECU
(
W ) L±Y
TO CHAK
CONNECTOR (
W )
L
TO ABS AND
TRACTION ECU
(
WA ) L
TO CHECK
CONNECTOR (
LP )
IK2
2
L
W
1E
1
SEAT BELT WARNING
RELAY [INTEGRATION RELAY] CHECK ENGINE
B
3
L±Y
IK1
20
FROM TURN
SIGNAL FLASHER
3D
10
3A2
3A 1
W±B
G±O
OIL
G±O
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26
ELECTRICAL WIRING ROUTING
Position of Parts in Engine Compartment
A 1 A/C Ambient Temp. Sensor E 1 ECT Solenoid
A 2 A/C Lock Sensor and A/C Magnetic Clutch E 2 EFI Water Temp. Sensor
A 3 A/C High Pressure SW E 3 EGR Gas Temp. Sensor (for USA Spec.)
A 4 ABS Actuator E 5 Engine Hood Courtesy SW
A 5 ABS Actuator (w/ Traction Control) E 6 Engine Oil Level Warning SW
A 6 ABS Actuator (w/ Traction Control)
A 7 ABS Speed Sensor Front LH F 1 Front Airbag Sensor LH
A 8 ABS Speed Sensor Front RH F 2 Front Airbag Sensor RH
A 9 Air Flow Meter F 3 Front Clearance Light LH
A 10 Alternator F 4 Front Clearance Light RH
A 11 Alternator F 5Front Side Marker Light LH
A 33 ABS Actuator (w/o Traction Control) F 6 Front Side Marker Light RH F 7 Front Turn Signal Light LH
B 1 Brake Fluid Level SW F 8 Front Turn Signal Light RH
B 6 Back±Up Light SW (for M/T) F 9 Fuse Block
C 3 Check Connector H 1 Headlight Hi LH
C 6 Cornering Light LH H 2 Headlight Hi RH
C 7 Cornering Light RH H 3 Headlight Lo LH
C 8 Cruise Control Actuator H 4 Headlight Lo RH H 5 Horn LH
D 13 Distributor H 6 Horn RH
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67
2. CONTROL SYSTEM
*EFI (ELECTRONIC FUEL INJECTION) SYSTEM
THE EFI SYSTEM MONITORS THE ENGINE CONDITION THROUGH THE SIGNALS INPUT FROM EACH SENSOR (IN\
PUT SIGNALS
FROM (1) TO (13) ETC.) TO THE ECU. THE BEST FUEL INJECTION TIMING IS DECIDED BASED ON THIS DATA AND THE PROGRAM
MEMORIZED BY THE ECU, AND THE CONTROL SIGNAL IS OUTPUT TO TERMINALS #10, #20, #30, #40, #50 AND #60 OF THE ECU TO
OPERATE THE INJECTOR. (INJECT THE FUEL). THE EFI SYSTEM PRODUCES CONTROL OF FUEL INJECTION OPERATION BY THE
ECU IN RESPONSE TO THE DRIVING CONDITIONS.
* ESA (ELECTRONIC SPARK ADVANCE) SYSTEM
THE ESA SYSTEM MONITORS THE ENGINE CONDITION THROUGH THE SIGNALS INPUT TO THE ECU FROM EACH SENSOR (INPUT
SIGNALS FROM (1), (2), (4) TO (13) ETC.). THE BEST IGNITION TIMING IS DECIDED ACCORDING TO THIS DATA AND THE
MEMORIZED DATA IN THE ECU AND THE CONTROL SIGNAL IS OUTPUT TO TERMINAL IGT THIS SIGNAL CONTROLS THE IGNITER
TO PROVIDE THE BEST IGNITION TIMING FOR THE DRIVING CONDITIONS.
* OXYGEN SENSOR HEATER CONTROL SYSTEM (USA SPEC.)
THE OXYGEN SENSOR HEATER CONTROL SYSTEM TURNS THE HEATER ON WHEN THE INTAKE AIR VOLUME IS LOW (TEMP. OF
EXHAUST EMISSIONS IS LOW), AND WARMS UP THE OXYGEN SENSOR TO IMPROVE DETECTION PERFORMANCE OF THE
SENSOR.
THE ECU EVALUATES THE SIGNALS FROM EACH SENSOR (INPUT SIGNALS FROM (1), (2), (4)\
, (9) TO (11) ETC.,) AND OUTPUTS
CURRENT TO TERMINAL HT TO CONTROL THE HEATER.
* ISC (IDLE SPEED CONTROL) SYSTEM
THE ISC SYSTEM (STEP MOTOR TYPE) INCREASES THE RPM AND PROVIDES IDLING STABILITY FOR FAST IDLE±UP WHEN THE
ENGINE IS COLD, AND WHEN THE IDLE SPEED HAS DROPPED DUE TO ELECTRICAL LOAD AND SO ON. THE ECU EVALUATES
THE SIGNALS FROM EACH SENSOR (INPUT SIGNALS FROM (1), (4), (5), (8)\
, (9), (11) ETC.), OUTPUTS CURRENT TO TERMINAL ISC1,
ISC2, ISC3 AND ISC4 TO CONTROL ISC VALVE.
* EGR CONTROL SYSTEM
THE EGR CONTROL SYSTEM DETECTS THE SIGNAL FROM EACH SENSOR (INPUT SIGNALS \
FROM (1), (4), (9), (10) ETC.), AND
OUTPUTS CURRENT TO TERMINAL EGR TO CONTROL THE EGR VALVE.
* FUEL PUMP CONTROL SYSTEM
THE COMPUTER OUTPUTS CURRENT TO TERMINAL FPC AND CONTROLS THE FUEL PUMP ECU AND FUEL PUMP DRIVE SPEED
IN RESPONSE TO CONDITIONS.
* ACIS (ACOUSTIC CONTROL INDUCTION SYSTEM)
ACIS INCLUDES A VALVE IN THE BULKHEAD SEPARATING THE SURGE TANK INTO TWO PARTS. THIS VALE IS OPENED AND
CLOSED IN ACCORDANCE WITH THE DRIVING CONDITIONS TO CONTROL THE INTAKE MANIFOLD LENGTH IN TWO STAGES FOR
INCREASED ENGINE OUTPUT IN ALL RANGES FROM LOW TO HIGH SPEEDS.
THE ECU JUDGES THE VEHICLE SPEED BY THE SIGNALS ((4), (5)) FROM EACH \
SENSOR AND OUTPUTS SIGNALS TO THE
TERMINAL ACIS TO CONTROL THE VSV (FOR OPENING AND CLOSING THE INTAKE CONTROL VALVE).
3. DIAGNOSIS SYSTEM
WITH THE DIAGNOSIS SYSTEM, WHEN THERE IS A MALFUNCTION IN THE ECU SIGNAL\
SYSTEM, THE MALFUNCTIONING SYSTEM IS
RECORDED IN THE MEMORY. THE MALFUNCTIONING SYSTEM CAN BE FOUND BY READING THE CODE DISPLAYED BY THE
CHECKING ENGINE WARNING LIGHT.
4. FAIL±SAFE SYSTEM
WHEN A MALFUNCTION HAS OCCURRED IN ANY SYSTEM, IF THERE IS A POSSIBILITY OF \
ENGINE TROUBLE BEING CAUSED BY
CONTINUED CONTROL BASED ON THE SIGNALS FROM THAT SYSTEM, THE FAIL±SAFE SYSTEM EITHER CONTROLS THE SYSTEM
BY USING DATA (STANDARD VALUES) RECORDED IN THE ECU MEMORY OR ELSE STOPS THE ENGINE.
NOTE: THE SPECIFICATION DESCRIPTIONS ªUSA SPEC.º AND ªEXC. USA SPEC.º USED IN THIS SECTION INDICATE THE
FOLLOWING SPECIFICATIONS.
USA SPEC. : USA (50 STATES) SPECIFICATIONS
EXC. USA SPEC. : USA (EXCEPT CALIFORNIA) AND CANADIAN SPECIFICATIONS.
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70
ENGINE CONTROL
I22E18
E17
A
2
SP1 A
33
BATT B
76
NSW A
32
+B1 A
31
+B
A
6 W
A
4 STP
B
77 STA
B
20 #10
B
18 #30
B
15 #60
B
19 #20
B
58 IGF
B
57 IGT
A
1
IGSW
B
3
A
10
A
1A 15 A13 A 14
54
12
IJ2
11
EB1
4
IG2
7
IK2
9
IJ2
3
3A
4
3D
13
+B TACHIGF IGT
B±R
B±O B±O
L±R B Y
B
G±W R
L±R Y
B±Y
B±W
B±R
B±O
BB
L±Y
IH L±Y
L±Y
BR
L±Y
W±YR±YB±Y
L±R B Y
B
G±W L±Y
B
W±L
B
L±Y
BR
Y
R
L±R
PP
P
B±Y
B±W
B±OB±R
B±R B±Y
B±O
CHECK ENGINE
COMBINATION METER
ENGINE ECU
(
M/T )
IGNITERTO TACHO METER
E11 , E1 2AB
I2
C13 , C 1 4
A
B I33
B
34 B 32 B 35 B33
E15
B
16
A
24 B
17
B±Y W B±R
B±R
B±R
G±Y V±R
L±W
LG±B
B±R
B±R
1346 25
ISC VALVE
I1
ISC2 ISC4 ISC1 ISC3
#40
#50
M±REL
B±R B±O
W
C±
3
B±O
FROM IGNITION
CO IL
ENGINE AND ECT ECU (
A/T )
E9 , E10
AB
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73
* 1 : W/ CD PLAYER
* 3 : FOR USA SPEC. *2:W/OCDPLAYER
8 13 715 2
3411912 8 3
E20 I32
I32
IJ 1 1 IK1
3
IK1
4
IK1
5IK1 2
EB1
2II1 5
B
4 E11
B
69 E1
B
28 VF2
B
29 VF1
A
20 TE1
A
3 KD
A
17 TT
A
23
ACMG A
34
A/C
IF
ED
BR
WGB
L±Y
B±R BR
B±R B±R
B±RLG
GR±Y
W
L±O
L±R W
GR±Y LG
GR±Y LG
B±Y BR
GR±Y LG
G±R
G±Y G±R
L
BR
L±Y B±R
B
G
W
BR
W
E1
+B
IG±
FP
OX
E1
OX2 TE1 VF1 ENG TE1 TT TE2 E11 , E1 2
T6
C3
FROM A/C MAGNETIC
CLUTCH RELAY
FROM A/C CONTROL
ASSEMBLY
ENGINE ECU (
M/T )
CHECK CONNE CTOR TDCL
(TOTAL DIAGNOSTIC
COMMUNICATION LINK )
A
B
IJ 1 12
R±L
I33
I32
BR
15 VF2
14
BR
BR
EC
E9 ,E10
ENGINE AND ECT ECU
(
A/T )
AB
IH1
2 IJ2
17
1 2IH1
1
A
19 TE 2
G±Y
W±B W±B L L
( SHIELDED )
(
SHIELDED )
B±R
BR B±R
(
SHIELDED )
KICK DOWN
SW
K3
BR
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