ECU LEXUS SC400 1991 Service Repair Manual

37. DISCONNECT ENGINE WIRE FROM LH CYLINDER HEAD
Remove the five bolts, and disconnect the engine wire.
38. REMOVE ENGINE HANGERS Remove the two bolts and engine hanger. Remove the two
engine hangers.
39. REMOVE CYLINDER HEAD COVERS Remove the eight bolts, seal washers, cylinder head cover
and gasket. Remove the two cylinder head covers.
40. IF NECESSARY, REMOVE SEMI±CIRCULAR PLUGS
41. REMOVE CAMSHAFTS NOTICE: Since the thrust clearance of the camshaft is
small, the camshaft must be held level while it is being
removed. If the camshaft is not kept level, the portion of
the cylinder head receiving the shaft thrust may crack or
be damaged, causing due the camshaft to seize or break.
To avoid this, the following steps should be carried out.
A. Remove exhaust camshaft from RH cylinder head
(a) Bring the service bolt hole of the driven s ub±gear
upward by turning the hexagon wrench head portion of
the exhaust camshaft with a wrench.
(b) Secure the exhaust camshaft sub±gear to the driven
gear with a service bolt.
Recommended service bolt: Thread diameter 6 mm
Thread pitch 1.0 mm
Bolt length 16±20 mm (0.63±0.79 in.)
HINT: When removing the camshaft, make certain that the
torsional spring force of the sub±gear has been eliminated by
the above operation.
EM±70
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ENGINE MECHANICAL Cylinder Heads
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C. Remove exhaust camshaft from LH cylinder head(a) Bring the service bolt hole of the driven s ub±gear
upward by turning the hexagon wrench head portion of
the exhaust camshaft with a wrench.
(b) Secure the exhaust camshaft sub±gear to the driven gear with a service bolt.
Recommended service bolt: Thread diameter 6 mm
Thread pitch 1.0 mm
Bolt length 16±20 mm (0.63±0.79 in.)
HINT: When removing the camshaft, make certain that the
torsional spring force of the sub±gear has been eliminated by
the above operation.
(c) Set the timing mark (two dot marks) of the camshaft
driven gear at approx. 155 angle by turning the hexagon
wrench head portion of the exhaust camshaft with a
wrench.
(d) Alternately loosen and remove the two bearing cap bolts
holding the intake camshaft side of the oil feed pipe to
the cylinder head.
(e) Uniformly loosen and remove the eight bearing cap bolts in several passes in the sequence shown.
(f) Re mo ve th e oil fe e d pip e , fo u r be a rin g ca p s an d
exhaust camshaft.
D. Remove intake camshaft from LH cylinder head (a) Remove the front bearing cap.
(b) Set the timing mark ( one dot mark) of the camshaft drive
gear at approx. 605 angle by turning the hexagon
wrench head portion of the intake camshaft with a
wrench.
EM±72
±
ENGINE MECHANICAL Cylinder Heads
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13. DISCONNECT ENGINE WIRE FROM CABIN(a) Remove the two clips, and pull out the instrument panelunder cover.
(b) Remove the four mounting screws.
(c) Disc onnect the connectors, and remove the lower
instrument panel finish panel and glove compartment
door assembly.
(d) Pull out the scuff plate.
(e) Take out the front side of the floor carpet.
(f) Remove the two nuts and ECU protector.
(g) Remove the nut, and disconnect the engine (& ECT) ECU from the floor panel.
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ENGINE MECHANICAL Cylinder BlockEM±69
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(h) Disconnect the following connectors:(1) Two connectors from engine (& ECT) ECU
(2) Connector from ABS & TRAC ECU
(3) Two connectors from TRAC ECU
(4) Four connectors from connector cassette
(5) Connector from A/C control assembly
(i) Pull out the engine wire from the cabin.
14. DISCONNECT PS PIPE FROM ENGINE Remove the two clamp bolts, and disconnect the PS pipe.
15. DISCONNECT HOSE, STARTER WIRE AND GROUND STRAP
(a) Remove the union bolt and two gaskets, disconnect thefuel inlet hose, and suspend the hose union end
upward.
HINT:
w Put a suitable container or shop towel under the fuel
pipe support.
w Slowly loosen the union bolt.
(b) Remove the nut and disconnect the starter wire.
(c) Disconnect the starter wire from the wire clamp.
(d) Disconnect the ground strap from the transmission.
16. (M/T)
DISCONNECT CLUTCH RELEASE CYLINDER FROM TRANS-
MISSION
Remove the two bolts and pull out the release cylinder.
EM±70
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ENGINE MECHANICAL Cylinder Block
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6. (M/T)INSTALL CLUTCH RELEASE CYLINDER
Install the clutch release cylinder and torque the two bolts.
Torque: 12 N Vm (120 kgf Vcm, 9 ft Vlbf)
7. INSTALL GROUND STRAP, STARTER WIRE AND HOSE
(a) Install the ground strap to the transmission.
(b) Install the starter wire with the nuts.
(c) Install the starter wire with the wire clamp.
(d) Install two new gaskets and fuel inlet hose with the union
bolt.
Torque: 34 N Vm (350 kgf Vcm, 25 ft Vlbf)
8. INSTALL PS PIPE
Install the PS pipe with the two clamp bolts.
9. CONNECT ENGINE WIRE TO CABIN (a) Push in the engine wire through the cowl panel.
(b) Connect the following connectors:(1) Two connectors to ECM
(2) Connectors to ABS & TRAC ECU
(3) Two connectors to TRAC ECU
(4) Four connectors to connector cassette
(5) Connector to A/C control assembly
EM±106
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ENGINE MECHANICAL Cylinder Block
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(c) Install the engine (& ECT) ECU with the nut.
(d) Install the ECU cover with the two nuts.
(e) Install the floor carpet.
(f) Install the scuff plate.
(g) Connect the connectors.
(h) Install the lower instrument panel finish panel and glovecompartment door assembly with the four screws.
(i) Install the instrument panel under cover with the two clips.
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ENGINE MECHANICAL Cylinder BlockEM±107
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Idle Speed Control (ISC) Valve
ON±VEHICLE INSPECTION
INSPECT ISC VALVE FOR OPERATING SOUNDCheck that there is a clicking sound immediately after stop-
ping the engine.
If the rpm operation is not as specified, check the ISC valve,
wiring and ECU.
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EFI SYSTEM Air Induction System (Idle Speed Control (ISC) Valve)FI±53
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(b) Insert a 0.40 mm (0.016 in.) feeler gauge, between thethrottle stop screw and stop lever.
(c) Connect the test probe of an ohmmeter to the terminals
IDL1 and E2 of the sensor.
(d) Gradually turn the sensor clockwise until the ohmmeter deflects, and secure it with the two set screws.
(e) Recheck the continuity between terminals IDL1 and E2.
Clearance between
lever and stop screwContinuity (IDL1±E2)
0.40 mm (0.016 in.)Continuity
0.65 mm (0.026 in.)No continuity
3. (w/ TRAC) INSPECT SUB±THROTTLE ACTUATOR, SUBTHROTTLE
VALVE AND SUB±THROTTLE POSITION SENSOR
A. Inspect sub±throttle actuator Using an ohmmeter, measure the resistance between the ter-
minals (ACM±A and , BCM±B and B).
Resistance: 0.5±1.0

If the resistance is not as specified, replace the actuator
valve.
B. Inspect sub±throttle actuator Remove the three screws and sub±throttle actuator.
FI±74
EFI SYSTEM
± Air Induction System (Throttle Body)
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(d) Gradually turn the sensor clockwise until the ohmmeterdeflects, and secure it with the two set screws.
(e) Recheck the continuity between terminals IDL2 and E2.
Clearance between
lever and stop screwContinuity (IDL2±E2)
0.30 mm (0.012 in.)Continuity
0.50 mm (0.020 in.)No continuity
E. Reinstall sub±throttle actuator Install the sub±throttle actuator with the three screws.
FI±76
EFI SYSTEM
± Air Induction System (Throttle Body)
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Replace the ECU
Zero againAfter replacing
the oxygen sensor
Normal
8 times
or moreZero
Check the number of times the voltmeter needle fluctuates in 10 seconds
Zero
8 times or more
Warm up the oxygen sensors with the engine at 2,500 rpm
for approx. 120 seconds
Connect terminals TE1 and E1 of the check connector.
And maintain engine at 2,500 rpm
Warm up the engine sensors with the engine at 2,500 rpm
for approx. 120 seconds. And maintain engine at 2,500 rpm.
Check the number of times the voltmeter needle
fluctuates in 10 seconds.
Less than 8 times
Disconnect terminals TE1 and E1 of the check connector.
And maintain engine at 2,500 rpm.
Measure voltage between terminals VF1 (VF2) and E1.
Less than 8 times
More than 0V
0V
Normal code, code
Nos. 21, 25, and 26Malfunction code(s)
(Ex. code Nos. 21, 25 and 26
Read and record diagnostic codes. (See TR section)
Repair the relevant diagnostic code
Disconnect terminals TE1 and E1 of the check connector.
And maintain engine at 2,500 rpm.
Read and record diagnostic codes. (See TR section)
Malfunction code(s)
(Ex. code Nos. 21, 25 and 26
Normal code, code
Nos. 21, 25, and 26
Repair the relevant diagnostic code
FI±74±
EFI SYSTEM Electronic Control System (Main Oxygen Sensors)
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