ABS LEXUS SC400 1991 Service Repair Manual

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
±
ENGINE MECHANICAL Cylinder Block
WhereEverybodyKnowsYourName

FUEL SYSTEM
Fuel is pumped up by the fuel pump, which flows through the fuel filter unde\
r pressure through the fuel pipe
to the delivery pipe where it is distributed to each injector. The fuel pressure regulator adjusts the pressure of the fuel from the fuel \
line (high pressure side) to a pressure
284 kPa (2.9 kgf/cm2, 41 psi) higher than the pressure inside the intake \
manifold, and excess fuel is returned
to the fuel tank through the return pipe.
When the engine is hot, the fuel pressure is increased to control percolation in the fuel system and impr\
ove
restartability and idling stability.
The pulsation damper absorbs the slight fluctuations in fuel pressure ca\
used by the injector.
The injectors operate on input of injection signals from the ECU and inj\
ect fuel into the intake manifold.
FI±6
±
EFI SYSTEM Operation
WhereEverybodyKnowsYourName

FUEL SYSTEM
Fuel is pumped up by the fuel pump, which flows through the fuel filter under pr\
essure through the fuel pipe
to the delivery pipe where it is distributed to each injector and the cold\
start injector.
The fuel pressure regulator adjusts the pressure of the fuel from the fuel \
line (high pressure side) to a pres-
sure 284 kPa (2.9 kgf/cm
2, 41 psi) higher than the pressure inside the intake manifold, and exce\
ss fuel is re-
turned to the fuel tank through the return pipe.
When the engine is hot, the fuel pressure is increased to control percolatio\
n in the fuel system and improve
restartability and idling stability.
The pulsation damper absorbs the slight fluctuations in fuel pressure ca\
used by the injector.
The injectors operate on input of injection signals from the ECU and inj\
ect fuel into the intake manifold.
The cold start injector operates when starting with low coolant temperature or at normal temperature
ranges, injecting fuel into the air intake chamber to improve startability. FI±7
EFI SYSTEM
± Operation
WhereEverybodyKnowsYourName

IF VEHICLE IS EQUIPPED WITH MOBILE
RADIO SYSTEM (HAM, CB, ETC.)
The ECU has been designed so that it will not be affected by out-
side interference. However, if your vehicle is equipped with a CB
radio transceiver, etc. (even one with about 10 W output), it may,
at times, have an effect upon ECU operation, especially if the an-
tenna and feeder are installed nearby.
Therefore, observe the following precautions:
1. Install the antenna as far away as possible from the ECU. The ECU is located on the floor panel on the passenger side
so the antenna should be installed at the rear of the vehicle.
2. Keep the antenna feeder as far away as possible from the ECU wires±at least 20 cm (7.87 in.) ±and, especially, do not
wind them together.
3. Check that the feeder and antenna are properly adjusted.
4. Do not equip your vehicle with a powerful mobile radio
system.
5. Do not open the cover or the case of the ECU unless absolutely necessary. (If the IC terminals are touched, the IC
may be destroyed by static electricity.)
AIR INDUCTION SYSTEM
1. Separation of the engine oil dipstick, oil filler cap, PCV hose,
etc. may cause the engine to run out of tune.
2. Disconnection, looseness or cracks in the parts of the air
induction system between the throttle body and cylinder
head will cause air suction and cause the engine to run out
of tune.
ELECTRONIC CONTROL SYSTEM
1. Before removing EFI wiring connectors, terminals, etc., firstdisconnect the power by either turning the ignition switch
OFF or disconnecting the battery terminals.
HINT: Always check the diagnosis code before disconnecting
the battery terminals.
2. When installing the battery, be especially careful not to
incorrectly connect the positive (+) and negative (±) cables.
3. Do not permit parts to receive a severe impact during removal or installation. Handle all EFI parts carefully, especially the
ECU.
4. Do not be careless during troubleshooting as there are numerous transistor circuits and even slight terminal contact
can cause further troubles.
5. Do not open the ECU cover.
6. When inspecting during rainy weather, take care to prevent entry of water. Also, when washing the engine compartment,
prevent water from getting on the EFI parts and wiring
connectors.
7. Parts should be replaced as an assembly.
FI±12
±
EFI SYSTEM Inspection Precautions
WhereEverybodyKnowsYourName

IF VEHICLE IS EQUIPPED WITH MOBILE
RADIO SYSTEM (HAM, CB, ETC.)
The ECU has been designed so that it will not be affected by out-
side interference. However, if your vehicle is equipped with a CB
radio transceiver, etc. (even one with about 10 W output), it may,
at times, have an effect upon ECU operation, especially if the an-
tenna and feeder are installed nearby.
Therefore, observe the following precautions:
1. Install the antenna as far away as possible from the ECU. The
ECU is located on the floor panel on the passenger side so
the antenna should be installed at the rear of the vehicle.
2. Keep the antenna feeder as far away as possible from the ECU wires±at least 20 cm (7.87 in.)±and, especially, do not
wind them together.
3. Check that the feeder and antenna are properly adjusted.
4. Do not equip your vehicle with a powerful mobile radio
system.
5. Do not open the cover or the case of the ECU unless absolutely necessary. (If the IC terminals are touched, the IC
may be destroyed by static electricity.)
AIR INDUCTION SYSTEM
1. Separation of the engine oil dipstick, oil filler cap, PCV hose,
etc. may cause the engine to run out of tune.
2. Disconnection, looseness or cracks in the parts of the air induction system between the throttle body and cylinder
head will cause air suction and cause the engine to run out
of tune.
ELECTRONIC CONTROL SYSTEM
1. Before removing EFI wiring connectors, terminals, etc., firstdisconnect the power by either turning the ignition switch
OFF or disconnecting the battery terminals.
HINT: Always check the diagnosis code before disconnecting
the battery terminals.
2. When installing the battery, be especially careful not to
incorrectly connect the positive (+) and negative (±) cables.
3. Do not permit parts to receive a severe impact during removal or installation. Handle all EFI parts carefully, especially the
ECU.
4. Do not be careless during troubleshooting as there are numerous transistor circuits and even slight terminal contact
can cause further troubles.
5. Do not open the ECU cover.
6. When inspecting during rainy weather, take care to prevent entry of water. Also, when washing the engine compartment,
prevent water from getting on the EFI parts and wiring
connectors.
7. Parts should be replaced as an assembly. FI±13
EFI SYSTEM
± Inspection Precautions
WhereEverybodyKnowsYourName

(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.
(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
±
ENGINE MECHANICAL Cylinder BlockEM±125
WhereEverybodyKnowsYourName

35. DISCONNECT TRANSMISSION CONTROL RODRemove the nut, and disconnect the control rod from the shift
lever.
36. REMOVE ENGINE AND TRANSMISSION A SSEMBLY
FROM VEHICLE
(a) Attach the engine hoist chain to the engine hangers.
(b) Remove the two nuts holding the engine mounting insulators to the front suspension crossmember.
(c) Remove the four bolts, four nuts and rear engine mounting member. Disconnect the ground strap.
(d) Lift the engine out of the vehicle slowly and carefully.
NOTICE: Be careful not to hit the PS gear housing, neu-
tral start switch and ABS actuator.
(e) Make sure the engine is clear of all wiring, hoses and cables.
(f) Place the engine and transmission assembly onto the stand.
EM±128
±
ENGINE MECHANICAL Cylinder Block
WhereEverybodyKnowsYourName

(c) Connect the following connectors:(1) Two connectors to engine & ECT ECU
(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
(d) Install the engine & ECT ECU with the nut.
(e) Install the ECU protector with the two nuts.
(f) Install the floor carpet.
EM±170
±
ENGINE MECHANICAL Cylinder Block
WhereEverybodyKnowsYourName

FUEL SYSTEM
Fuel is pumped up by the fuel pump, which flows through the fuel filter under pr\
essure through the fuel pipe
to the delivery pipe where it is distributed to each injector and the cold\
start injector.
The fuel pressure regulator adjusts the pressure of the fuel from the fuel \
line (high pressure side) to a pres-
sure 284 kPa (2.9 kgf/cm
2, 41 psi) higher than the pressure inside the intake manifold, and exce\
ss fuel is re-
turned to the fuel tank through the return pipe.
When the engine is hot, the fuel pressure is increased to control percolatio\
n in the fuel system and improve
restartability and idling stability.
The pulsation damper absorbs the slight fluctuations in fuel pressure ca\
used by the injector.
The injectors operate on input of injection signals from the ECU and inj\
ect fuel into the intake manifold.
The cold start injector operates when starting with low coolant temperature or at normal temperature
ranges, injecting fuel into the air intake chamber to improve startability. FI±7
EFI SYSTEM
± Operation
WhereEverybodyKnowsYourName

Diag. Code 35High Altitude Compensator Sensor
(HAC Sensor) Circuit
CIRCUIT DESCRIPTION
The HAC sensor is built into the ECU. This is a semiconductor pressure sens\
or with properties which cause its
electrical resistance to change when stress is applied to the sensor's crystal (silicon) (piezoelectric effect). This
sensor is used to detect the atmospheric (absolute) pressure and outputs cor\
responding electrical signals. Fluc-
tuations in the air pressure cause changes in the intake air density, which can cause deviations in the air±fuel
ratio. The signals from HAC sensor are used to make corrections for these fluct\
uations. If the ECU records diag-
nostic code º35º, the fail safe function operates and the atmospheric pressure is set at a\
constant 760 mmHg.
Code No.Diagnostic Code Detecting ConditionTrouble Area
35Open or short detected in HAC sensor circuit for 0.5
sec. or more.
ECU
DIAGNOSTIC CHARTDIAGNOSTIC CHART
Are there any other codes (besides Code 16)
being output?
Replace engine & ECT ECU. Go to relevant diag. code chart.
TR±92±
ENGINE TROUBLESHOOTING Circuit Inspection
WhereEverybodyKnowsYourName