ECU LEXUS SC400 1991 Service Repair Manual

FAIL±SAFE CHART
If any of the following codes is recorded, the ECU enters fail±
safe mode.
Code No.Fail±Safe OperationFail±Safe Deactivation Conditions
14Fuel cut1 IGF1 detected in consecutive 8 ignitions.
15Fuel cut1 IGF2 detected in consecutive 8 ignitions.
16Torque control prohibited.Returned to normal condition.
22THW is fixed at 805C (176 5F).Returned to normal condition.
24THA is fixed at 20 5C (68 5F).Returned to normal condition.
31
Ignition timing controlled between 10 5 ~ 30 5
BTDC,
Injection time controlled between 3 msec. ~ 30 m
sec., in relation to:
w Engine rpm
w Throttle angle
w ISC step value
KS input 15 times/sec. or more.
35Atmospheric pressure is fixed at 760 mmHg.Returned to normal condition.
The following 1 or 2 must be repeated at least 2
times consecutively.
41VTA1 is fixed at 051 When IDL is ON41VTA1 is fixed at 051 When IDL is ON
0.25 V
VTA1
0.95 V
2 When IDL is OFF2 When IDL is OFF
0.25 V
VTA1
4.9 V
The following 1 or 2 must be repeated at least 2
times consecutively.
47Value of VTA1 is used1 When IDL2 is ON47Value of VTA1 is used.1 When IDL2 is ON
0.25 V
VTA2
0.95 V
2 When IDL2 is OFF2 When IDL2 is OFF
0.25 V
VTA2
4.9 V
52Max. timeing retardation.IG switch OFF.
53Max. timeing retardation.Returned to normal condition.
55Max. timeing retardation.IG switch OFF.
Back±Up Function
If there is trouble with the program in the ECU and the ignition signals\
(IGT) are not output, the ECU controls
fuel injection and ignition timing at predetermined levels as a back±up f\
unction to make it possible to continue
to operate the vehicle.
Furthermore, the injection duration is calculated from the satrting sign\
al (STA) and the throttle position signal
(IDL). Also, the ignition timing is fixed at the initial ignition timing, 5 5 BTDC, without relation to the engine speed.
HINT: If the engine is controlled by the back±up function, the CHECK ENGIN\
E light lights up to warn the driver
of the malfunction but the diagnostic code is not output. TR±22
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ENGINE TROUBLESHOOTING Fail±Safe Chart
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CHECK FOR MOMENTARY
INTERRUPTION
As described in the preceding paragraph, abnormality detection
ability in the test mode is increased compared to that in the normal
mode, so that when momentary interruptions or momentary shorts
occur in the ECU signal circuits (G1, G2, NE, THW, THA, VTA1,
VTA2) shown in the table below, the appropriate diagnostic code
is output.
Accordingly, when the diagnostic codes shown in the table below
(13, 22, 24, 41, 47) are output during the diagnostic code check,
and inspection of the appropriate circuits reveals no abnormality,
perform the check for momentary interruption as described below.
By performing the check for momentary interruption, the place
where momentary interruptions or momentary shorts are occur-
ring due to poor contacts can be isolated.
CLEAR DIAGNOSTIC CODES
See page TR±13.
SET TEST MODE
1. With the ignition switch off, using SST, connect the terminals
TE2 and E1 of the TDCL.
SST 09843±18020
2. Start the engine and check to see the ºCHECKº engine warning light to go off.
PERFORM A SIMULATION TEST
Using the symptom simulation (See page IN±20), apply vibration
to and pull lightly on the wire harness, connector or terminals in the
circuit indicated by the malfunction code.
In this test, if the ºCHECKº engine warning light lights up, it in\
di-
cates that the place where the wire harness, connector or termi-
nals being pulled or vibrated has faulty contact. Check that point
for loose connections, dirt on the terminals, poor fit or other prob-
lems and repair as necessary.
HINT: After cancelling out the diagnostic code in memory and set
the test mode, if the ºCHECKº engine warning light does not go off
after the engine is started, check thoroughly for faulty contact,
etc., then try the check again. If the ºCHECKº engine warning light
still does not go off, check and replace ECU.
±
ENGINE TROUBLESHOOTING Check for Momentary InterruptionTR±23
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TERMINALS OF ECU
Connectors of the engine & ECT ECU are water±proof and are the
bolt type.
For water proof type connectors, in order to measure the voltage
of ECU terminals and the resistance of connected parts, connect
the inspection sub wire harness between the ECU and vehicle
wire harness, then perform the inspection. The inspection method
of inserting a tester probe from the other side of connector notice-
ably reduces the water±proof ability.
Disconnect the connector by fully loosening the bolt.
PREPARATION
1. Turn the ignition switch to LOCK position.
2. Turn up the passenger side floor mat.
3. Remove the ECU protector.
4. Disconnect the connector from the ECU. After completely loosening the bolt, the two parts of the con-
nector can be separated.
NOTICE:
w Do not pully the wire harness when disconnecting the
connector.
w When disconnecting the connector, the ECU's backup
power source is cut off, so the malfunction codes, etc.
recorded in the ECU memory are cancelled.
w Never insert a tester probe or male terminal used for
inspection purposes into the female terminal of the
vehicle wire harness. Otherwise, the female terminal may
be widened, which can result in faulty connection.
5. Connect the Check Harness A between ECU and connector
of vehicle wire harness.
SST 09990±01000
HINT: The arrangement of the check connector terminals are
the same as those of the ECU.
See page TR±31
6. Disconnect the Check Harness A.
7. Reconnect the connector to the ECU.
(a) Match the male connector correctly with the femaleconnector, then press them together.
(b) Tighten the bolt Make sure the connector is completely connected, by
tightening the bolt until there is a clearance of less than
1 mm (0.04 in.) between bottom of the male connector
and end of the female connector.
8. Install the ECU protector and floor mat.
TR±30
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ENGINE TROUBLESHOOTING Terminals of ECU
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TERMINALS OF ECU
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ENGINE TROUBLESHOOTING Terminals of ECUTR±31
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TERMINALS OF ECU (Cont'd)
TR±32±
ENGINE TROUBLESHOOTING Terminals of ECU
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STANDARD VALUE OF ECU TERMINALS
Symbols (Terminals No.)STD Voltage (V)Condition
BATT (A33) ± E1 (B69)10 ~ 14Always
IGSW (A1)IGSW (A1)
+ B (A31)± E1 (B69) 10 ~ 14IG switch ON+ B (A31)
+ B1 (A32)
E1 (B69)10 14IG switch ON
VC (B41)±E2 (B65)4.0 ~ 6.0IG switch ON
Below 1 0IG switch ON
IDL1 (B64)E2 (B65)
Below 1.0IG switch ON
Main or sub throttle valve fully closed.IDL1 (B64)
IDL2 (B63)± E2 (B65)
10 14IG switch ON()10 ~ 14IG switch ON
Main or sub throttle valve fully open.
01 10IG switch ON
VTA1 (B43)E2 (B65)
0.1 ~ 1.0IG switch ON
Throttle valve fully closed.VTA1 (B43)
VTA2 (B42)± E2 (B65)
30 60IG switch ON()3.0 ~ 6.0IG switch ON
Throttle valve fully open.
KS (B66) ± E1 (B69)Pulse generation(0 and 4 ~ 6)Idling
THA (B45) ± E2 (B65)1.0 ~ 3.0Idling, Intake air temp. 20 5C (68 5F).
THW (B44) ± E2 (B65)0.1 ~ 1.0Idling, Water temp. 80 5C (176 5F).
STA (B77) ± E1 (B69)6.0 or moreCranking
#10 (B20), #20 (B19)E01 (B80)10 ~ 14IG switch ON#10 (B20), #20 (B19)
#30 (B18), #40 (B17)± E01 (B80)Pulse generationIdling
IGT1 (B57), IGT2 (B56) ± E1 (B69)Pulse generation
(0 and 4 ~ 6)Idling
Below 1.0IG switch ON
IGF1 (B58), IGF2 (B59) ± E1 (B69)Pulse generation(0 and 4 ~ 6)Idling
G1 (B26), G2 (B25) ± G1
(B6)Pulse generation
(±1.0 ~ +1.0 or higher)Idling
NE (B27) ± NE
(B7)Pulse generation
(±0.8 ~ +0.8 or higher)Idling
MREL (A24) ± E1 (B69)10 ~ 14IG switch ON
4.2 ~ 6.0Cranking, Sudden racing (6,000 rpm)
FPC (A22) ± E1 (B69)Pulse generation (0 and 4 ~ 6)Idling
DI (A21) ± E1 (B69)7.5 or moreIdling
FPU (B73) E1 (B69)10 ~ 14IG switch ONFPU (B73) ± E1 (B69)Below 2.0Restarting high temp.
PAG (B74) ± E1 (B69)10 ~ 14Idling
±
ENGINE TROUBLESHOOTING Standard Value of ECU TerminalsTR±33
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STANDARD VALUE OF ECU TERMINALS (Cont'd)
Symbols (Terminals No.)STD Voltage (V)Condition
ISC1 (B35), ISC2 (B34)E1 (B69)10 14IG switch ONISC1 (B35), ISC2 (B34)
ISC3 (B33), ISC4 (B32)±E1 (B69)10 ~ 14IG switch ON
VF1 (B29), VF2 (B28) ± E1 (B69)1.0 ~ 4.0
Maintain engine speed at 2,500 rpm for two
minutes
after warming up then return to idling.
OXL1 (B48), OXR1 (B47) ± E1 (B69)Pulse generation(0 ~ 1.0)Maintain engine speed at 2,500 rpm for two
minutes
after warming up.
HTL1 (B71), HTR1 (B72)E01 (B80)Below 2.0IdlingHTL1 (B71), HTR1 (B72)
HTL2 (B52), HTR2 (B53)± E01 (B80)10 ~ 14IG switch ON
EGR1 (B39), EGR2 (B38)E1 (B69)*10 14IG switch ONEGR1 (B39), EGR2 (B38)
EGR3 (B37), EGR4 (B36)± E1 (B69)* 10 ~ 14IG switch ON
EGR (B39) ± E1 (B69)10 ~ 14IG switch ON
KNK1 (B50), KNK2 (B49) ± E1 (B69)Pulse generation
(Frequency : 6.6 KHz)Idling
NSW (B76) E1 (B69)
10 ~ 14IG switch ON
Other shift position in ºPº, ºNº ranges.
NSW (B76) ± E1 (B69)
Below 1.0IG switch ON
Shift position in ºPº, ºNº ranges.
SPD (A2)±E1 (B69)Pulse generation (0 and 10 ~ 14)IG switch ON
Rotate driving wheel slowly.
TE1 (A20) ± E1 (B69)10 ~ 14IG switch ON
TE2 (A19) ± E1 (B69)10 ~ 14IG switch ON
W (A6) E1 (B69)10 ~ 14IdlingW (A6)±E1 (B69)Below 2.0IG switch ON
AD (A11) ± E1 (B69)10 ~ 14Idling
ODI (A12) ± E1 (B69)4.0 ~ 6.0IG switch ON
A/C (A34) E1 (B69)Bellow 2.0A/C switch ON (At idling)A/C (A34) ± E1 (B69)10 ~ 14A/C switch OFF
ACMG (A23) E1 (B69)Below 2.0A/C switch ON (At idling)ACMG (A23)±E1 (B69)10 ~ 14A/C switch OFF
TR (A37) ± E1 (B69)10 ~ 14IG switch ON
Below 1 0IG switch ON
VTO1 (A40)E2 (B65)
Below 1.0IG switch ON
Main or sub throttle valve fully closed.VTO1 (A40)
VTO2 (A39)± E2 (B65)
30 55IG switch ON()3.0 ~ 5.5IG switch ON
Main or sub throttle valve fully open.
NEO (A38) ± E1 (B69)4.0 ~ 6.0IG switch ON
* Only for USA specification vehicles. TR±34
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ENGINE TROUBLESHOOTING Standard Value of ECU Terminals
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CIRCUIT INSPECTIONDiag. Code 12
RPM Signal Circuit (No.1)
CIRCUIT DESCRIPTION
Cam position sensors (G1 and G2 signals) and engine speed sensor (NE sig\
nal) consist of a signal plate
and a pick up coil.
The G1, G2 signal plates have one tooth each on its outer circumference and\
are mounted on the left and
right bank camshafts.
When the camshafts rotate, the protrusion on the signal plate and the air gap on the pick up coil change,
causing fluctuations in the magnetic field and generating an electromotive forc\
e in the pick up coil.
The NE signal plate has 12 teeth and is mounted on the crankshaft. The NE s\
ignal sensor generates 12
NE signals per engine revolution. The ECU detects the standard crankshaf\
t angle based on the G1, G2
signals, and the actual crankshaft angle and the engine speed by the NE \
signals.
Code No.Diagnostic Code Detecting ConditionTrouble Area
wOpen or short in engine speed sensor, No. 1,w Oen or short in engine s eed sensor, No. 1,
No. 2 cam position sensor circuit
12No ºNEº or ºG1º and ºG2º signal to ECU
No. 2 cam osition sensor circuit
w Engine speed sensor12No NE or G1 and G2 signal to ECU
within 2 sec. after cranking.
wEngine s eed sensor
wNo. 1, No. 2 cam position sensorgNo. 1, No. 2 cam osition sensor
wStarter
wECU
TR±48±
ENGINE TROUBLESHOOTING Circuit Inspection
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OKNG
OKNG
2Check for open and short in harness and connector between engine & ECT ECU an\
d each sen-
sor (See page IN±27).
Repair or replace harness or connector.
3Inspect sensor installation and teeth of signal plate.
Tighen the sensor.
Replace signal plate.
Check and replace engine and ECT ECU.
±
ENGINE TROUBLESHOOTING Circuit InspectionTR±51
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Diag. Code 13RPM Signal Circuit (No.2)
CIRCUIT DESCRIPTION
Refer to RPM signal circuit (No. 1) on page TR±48.
Code No.Diagnostic Code Detecting ConditionTrouble Area
No NE signal to ECU for 0.1 sec. or more at
1,000 rpm or more.
wOpen or short in engine speed sensor
w circuit.
w Engine speed sensor
w ECU
13No 12 pulses of NE to ECU during the interval
between G1 and G2 pulses.
wOpen or short in engine speed sensor
w circuit.
w Mechanical system malfunction (skipping
teeth of timing belt, belt stretched)
w Engine speed sensor
w ECU
Deviation in G (G1, G2) and NE signal contin-
ues for 1 sec. during idling (throttle fully
closed) after engine warmed up.wMechanical system malfunction (skipping
teeth of timing belt, belt stretched)
w No. 1, No. 2 cam position sensor
w ECU
DIAGNOSTIC CHARTDIAGNOSTIC CHART
Inspect sensor installation. Check if any teeth of NE
signal plate are broken
Check valve timing (Check for loose and jumping teeth
of timing belt (See page EM±51)). Tighten the sensor.
Replace signal plate.
Adjust valve timing
(Repair or replace timing belt).
HINT: Perform troubleshooting of diag. code 12 first. If no trouble is found, trouble\
shoot the following mechanical systems.
Check for momentary interruption
(See page TR±23).
TR±52±
ENGINE TROUBLESHOOTING Circuit Inspection
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