ESP LEXUS SC300 1991 Service Service Manual

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 driv\
ing condi-
tions, into the intake air mixture to slow down combustion, reduce the combust\
ion 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.
wCoolant temp. below 535C (127.45F)
w During deceleration (throttle valve
closed)
w Light engine load (amount of intake air
very small)
w Engine speed over 4,000 rpm
w Engine idling
w Neutral start switch on
Code No.Diagnostic Code Detecting ConditionTrouble 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 5C (149 5F) or below for
1 ~ 4 min. under conditions (a) and(b).
(2 trip detection logic)*
(a) Coolant temp.: 65 5C (149 5F) 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±21.
TR±108
±
ENGINE TROUBLESHOOTING
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DATE:NOVEMBER 29, 1996
TitleALTERNATE REFRIGERANTS AND A/C RETROFITPage 1 of 2
Effective January 1, 1996, the E.P.A. has officially banned the manufacture of Refrigerant 12 (Freon).
As a result, surplus supplies of R±12 will begin to dwindle over the ne\
xt several years until, eventually,
R±12 will no longer be available.
This uncertainty about the availability of R±12 has caused significant concerns for Lexus dealers when
servicing HVAC systems not using R±134a refrigerant. Similarly, the reduced availability of R±12 has
prompted demands for R±134a retrofit kits and/or alternate refrigerants. Thi\
s TSB will clarify Lexus's
current recommendations for servicing and retrofitting HVAC systems on Lexus vehicles using R±12
refrigerant.
ALTERNATE REFRIGERANTS:
Previously, the E.P.A. has endorsed other alternative refrigerants. These endorsements, combin\
ed with
the uncertain future availability of R±12, have lead to a limited accept\
ance of using alternative refrigerants
when servicing or retrofitting R±12 HVAC systems. Use of these refrigerants can lead to several service
related problems, including:
Poor system performance and leak detection capabilities.
Contamination of R±12 and R±134a during refrigerant recovery and r\
ecycling.
Recently the E.P.A. released a statement clarifying that approval of alternative refrige\
rants relates only
to the toxicology, flammability, ozone depletion and global warming characteristics. The approval does
not imply acceptability of alternative refrigerants use with respect to serviceability or performance.
TOYOTA MOTOR SALES, U.S.A. ENDORSES THE USE OF R±134a AS THE ONLY ACCEPTABLE ALTERNATIVE REFRIGERANT FOR VEHICLES USING R±12.
R±12 AVAILABILITY:
It is estimated that existing R±12 supplies will meet market demand i\
n 1996. Beyond that, Lexus will
supply R±12 to it's dealers from a strategic reserve. These strategic reserves are alloca\
ted specifically
for distribution to Lexus dealers for repair of their customers' R±12 H\
VAC systems. TMS projects these
reserves may meet dealer demand through early 1998. After that, we believe R±12 will no longer be re\
adi-
ly available and dealers will begin to retrofit customer vehicles with R\
±134a.
REF: HEATING & AIR CONDITIONING
NO:AC007±96
MODEL:ALL MODELS
WhereEverybodyKnowsYourName

DATE:NOVEMBER 29, 1996
TitleALTERNATE REFRIGERANTS AND A/C RETROFITPage 1 of 2
Effective January 1, 1996, the E.P.A. has officially banned the manufacture of Refrigerant 12 (Freon).
As a result, surplus supplies of R±12 will begin to dwindle over the ne\
xt several years until, eventually,
R±12 will no longer be available.
This uncertainty about the availability of R±12 has caused significant concerns for Lexus dealers when
servicing HVAC systems not using R±134a refrigerant. Similarly, the reduced availability of R±12 has
prompted demands for R±134a retrofit kits and/or alternate refrigerants. Thi\
s TSB will clarify Lexus's
current recommendations for servicing and retrofitting HVAC systems on Lexus vehicles using R±12
refrigerant.
ALTERNATE REFRIGERANTS:
Previously, the E.P.A. has endorsed other alternative refrigerants. These endorsements, combin\
ed with
the uncertain future availability of R±12, have lead to a limited accept\
ance of using alternative refrigerants
when servicing or retrofitting R±12 HVAC systems. Use of these refrigerants can lead to several service
related problems, including:
Poor system performance and leak detection capabilities.
Contamination of R±12 and R±134a during refrigerant recovery and r\
ecycling.
Recently the E.P.A. released a statement clarifying that approval of alternative refrige\
rants relates only
to the toxicology, flammability, ozone depletion and global warming characteristics. The approval does
not imply acceptability of alternative refrigerants use with respect to serviceability or performance.
TOYOTA MOTOR SALES, U.S.A. ENDORSES THE USE OF R±134a AS THE ONLY ACCEPTABLE ALTERNATIVE REFRIGERANT FOR VEHICLES USING R±12.
R±12 AVAILABILITY:
It is estimated that existing R±12 supplies will meet market demand i\
n 1996. Beyond that, Lexus will
supply R±12 to it's dealers from a strategic reserve. These strategic reserves are alloca\
ted specifically
for distribution to Lexus dealers for repair of their customers' R±12 H\
VAC systems. TMS projects these
reserves may meet dealer demand through early 1998. After that, we believe R±12 will no longer be re\
adi-
ly available and dealers will begin to retrofit customer vehicles with R\
±134a.
REF: HEATING & AIR CONDITIONING
NO:AC007±96
MODEL:ALL MODELS
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146
ABS (ANTI±LOCK BRAKE SYSTEM)
THIS SYSTEM CONTROLS THE RESPECTIVE BRAKE FLUID PRESSURES ACTING ON THE DISC\
BRAKE CYLINDERS OF THE RIGHT
FRONT WHEEL, LEFT FRONT WHEEL AND REAR WHEELS WHEN THE BRAKES ARE APPLIED IN \
A PANIC STOP SO THAT THE
WHEELS DO NOT LOCK. THIS RESULTS IN IMPROVED DIRECTIONAL STABILITY AND STEERABILITY DURING PANIC BRAKING.
1. INPUT SIGNALS
(1) SPEED SENSOR SIGNALTHE SPEED OF THE WHEELS IS DETECTED AND INPUT TO TERMINALS FL+, FR+, RL+ AND RR+ OF THE ABS ECU.
(2) STOP LIGHT SW SIGNAL A SIGNAL IS INPUT TO TERMINAL STP OF THE ABS ECU WHEN THE BRAKE PEDAL IS OPERATED.
(3) PARKING BRAKE SW SIGNAL A SIGNAL IS INPUT TO TERMINAL PKB OF THE ABS ECU WHEN THE PARKING BRAKE IS OPERATED.
2. SYSTEM OPERATION
DURING SUDDEN BRAKING, THE ABS ECU WHICH HAS SIGNALS INPUT FROM EACH SENSOR CONTROLS THE CURRENT FLOWING
TO THE SOLENOID INSIDE THE ACTUATOR AND LETS THE HYDRAULIC PRESSURE ACTING ON EACH WHEEL CYLINDER ESCAPE \
TO
THE RESERVOIR.
THE PUMP INSIDE THE ACTUATOR IS ALSO OPERATING AT THIS TIME AND IT RETURNS THE BRAKE FLUID FROM THE RESERVOIR
TO THE MASTER CYLINDER, THUS PREVENTING LOCKING OF THE VEHICLE WHEELS.
IF THE ECU JUDGES THAT THE HYDRAULIC PRESSURE ACTING ON THE WHEEL CYLINDER IS INSUFFICIENT, THE CURRENT
ACTING ON SOLENOID IS CONTROLLED AND THE HYDRAULIC PRESSURE IS INCREASED.
HOLDING OF THE HYDRAULIC PRESSURE IS ALSO CONTROLLED BY THE COMPUTER, BY THE SAME METHOD AS ABOVE. BY
REPEATED PRESSURE REDUCTION, HOLDING AND INCREASE ARE REPEATED TO MAINTAIN VEHICLE STABILITY AND TO IMPROVE
STEERABILITY DURING SUDDEN BRAKING.
A 4(B), A 33(A) ABS ACTUATOR
(A) 3, (A) 4±GROUND : ALWAYS APPROX. 12 VOLTS
(A) 1±GROUND : ALWAYS CONTINUITY
(B) 4, (B) 5, (B) 6±GROUND : APPROX. 1.15
(IGNITION SW OFF)
(B) 2±GROUND :APPROX. 5
(IGNITION SW OFF)
A 7, A 8, A30, A31 ABS SPEED SENSOR FRONT LH, RH, REAR LH, RH
1±2 : APPROX. 1.0KW (20 °C, 68°F)
A22(A), A23(B) ABS ECU
(B) 11±GROUND : APPROX. 12 VOLTS WITH IGNITION SW ON
(B) 2, (B) 13±GROUND : ALWAYS CONTINUITY
(B) 22±GROUND : ALWAYS APPROX. 12 VOLTS
(B) 1, (A) 6, (A) 12±GROUND : APPROX. 12 VOLTS WITH IGNITION SW ON
(B) 16±GROUND : CONTINUITY WITH PARKING BRAKE LEVER PULLED UP
(B) 7±GROUND : APPROX. 12 VOLTS WITH STOP LIGHT SW ON
P 3 PARKING BRAKE SW
1±GROUND : CLOSED WITH PARKING BRAKE LEVER PULLED UP
S12 STOP LIGHT SW
1±2 : CLOSED WITH BRAKE PEDAL DEPRESSED
SYSTEM OUTLINE
SERVICE HINTS
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139
(FOR ABS)
THIS SYSTEM CONTROLS THE RESPECTIVE BRAKE FLUID PRESSURES ACTING ON THE DISC\
BRAKE CYLINDERS OF THE RIGHT
FRONT WHEEL, LEFT FRONT WHEEL AND REAR WHEELS WHEN THE BRAKES ARE APPLIED IN \
A PANIC STOP SO THAT THE
WHEELS DO NOT LOCK. THIS RESULTS IN IMPROVED DIRECTIONALLY STABILITY AND STEERABILITY DURING PANIC BRAKING.
1. INPUT SIGNALS
(1) SPEED SENSOR SIGNALTHE SPEED OF THE WHEELS IS DETECTED AND INPUT TO TERMINALS FL+, FR+, RL+ AND RR+ OF THE ABS AND TRACTION
ECU.
(2) STOP LIGHT SW SIGNAL A SIGNAL IS INPUT TO TERMINAL STP OF THE ABS AND TRACTION ECU WHEN THE BRAKE PEDAL IS OPERATED.
(3) PARKING BRAKE SW SIGNAL A SIGNAL IS INPUT TO TERMINAL PKB OF THE ABS AND TRACTION ECU WHEN THE PARKING BRAKE IS OPERATED.
2. SYSTEM OPERATION
DURING SUDDEN BRAKING, THE ABS AND TRACTION ECU WHICH HAS SIGNALS INPUT FROM E\
ACH SENSOR CONTROLS THE
CURRENT FLOWING TO THE SOLENOID INSIDE THE ACTUATOR AND LETS THE HYDRAULIC PRESSURE ACTING ON EACH WHEEL
CYLINDER ESCAPE TO THE RESERVOIR. THE PUMP INSIDE THE ACTUATOR IS ALSO OPERATING AT THIS TIME AND IT RETURNS
THE BRAKE FLUID FROM THE RESERVOIR TO THE MASTER CYLINDER, THUS PREVENTING LOCKING OF THE VEHICLE WHEELS.
IF THE ECU JUDGES THAT THE HYDRAULIC PRESSURE ACTING ON THE WHEEL CYLINDER IS INSUFFICIENT, THE CURRENT
ACTING ON SOLENOID IS CONTROLLED AND THE HYDRAULIC PRESSURE IS INCREASED, HOLD\
ING OF THE HYDRAULIC
PRESSURE IS ALSO CONTROLLED BY THE COMPUTER, BY THE SAME METHOD AS ABOVE. BY REP\
EATED PRESSURE REDUCTION,
HOLDING AND INCREASE ARE REPEATED TO MAINTAIN VEHICLE STABILITY AND TO IMPROVE STEERABILITY DURING SUDDEN
BRAKING.
(FOR TRACTION CONTROL)
THE TRACTION CONTROL SYSTEM IS A SYSTEM WHEREBY THE ªABS AND TRACTION ECUº AND ªTRACTION ECUº\
CONTROLS THE
ENGINE TORQUE AND THE HYDRAULIC PRESSURE OF THE WHEEL CYLINDER OF THE DRIVING WHEELS IN ORDER TO CONTROL
SPINNING OF THE DRIVING WHEELS WHEN STARTING OFF AND ACCELERATING, AND PROVIDE THE MOST APPROPRIATE DRIVING
FORCE IN RESPONSE TO THE ROAD CONDITIONS FOR VEHICLE STABILITY.
TRACTION CONTROL OPERATION
VEHICLE SPEED SIGNALS FROM THE SPEED SENSOR INSTALLED ON EACH WHEEL ARE INPUT TO THE ABS AND TRACTION ECU.
WHEN THE ACCELERATOR PEDAL IS DEPRESSED WHILE DRIVING ON A SLIPPERY ROAD AND THE DRIVING WHEEL (REAR WHEEL)
SLIPS, IF THE ROTATION OF THE REAR WHEEL EXCEEDS THE ROTATION OF THE FRONT WHEELS FOR A SPECIFIED PERIOD, THE
ECU JUDGES THAT THE REAR WHEEL IS SLIPPING.
WHEN THIS OCCURS, CURRENT FLOWS FROM TRACTION ECU TO SUB THROTTLE ACTUATOR TO CLOSE THE SUB THROTTLE
VALVE. THE THROTTLE VALVE OPENING ANGLE SIGNAL IS OUTPUT FROM TERMINAL VTA OF SUB THROTTLE POSITION SENSOR
TO TERMINAL VTA2 OF ENGINE AND ECT ECU TO KEEP THE ENGINE RPM AT THE MOST SUITABLE LEVEL FOR THE DRIVING
CONDITIONS AND REDUCE SLIP OF THE DRIVING WHEEL. AT THE SAME TIME, OPERATION OF THE ABS AND TRACTION ECU
CAUSE THE TRACTION BRAKE ACTUATORS (ACC CUT, M/C CUT, RESERVOIR CUT SOLENOID) TO TURN ON TO SWITCH THE
HYDRAULIC CIRCUIT TO ªTRACTIONº MODE.
IN THIS CASE, SIGNALS ARE INPUT FROM TERMINAL SRR OF ABS AND TRACTION ECU TO TERMINAL (B)6 OF ABS ACTUATOR, AND
FROM TERMINAL SRL OF ABS AND TRACTION ECU TO TERMINAL (B)1 OF ABS ACTUATOR, CONTROLLING THE REAR WHEEL
SOLENOID IN THE ABS ACTUATOR AND INCREASING THE HYDRAULIC PRESSURE OF THE WHEEL CYLINDER IN ORDER \
TO
PREVENT SLIP.
TO MAINTAIN THE HYDRAULIC PRESSURE OF THE REAR WHEELS, THE REAR WHEEL SOLENOID I\
NSIDE THE ABS ACTUATOR IS
PUT IN ªHOLDº MODE AND KEEPS THE HYDRAULIC PRESSURE TO THE BRAKE CYLINDER CONSTANT.
WHEN THE BRAKE CYLINDER HYDRAULIC PRESSURE IS REDUCED, THE PRESSURE REDU\
CTION MODE REDUCES AND CONTROLS
THE HYDRAULIC PRESSURE.
SYSTEM OUTLINE
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151
7. AUTO CANCEL FUNCTION
A) IF ANY OF THE FOLLOWING OPERATING CONDITIONS OCCURS DURING CRUISE CONTROL OPERATION, THE SET SPEED IS
ERASED, CURRENT FLOW TO MAGNETIC CLUTCH IS STOPPED AND THE CRUISE CONTROL IS RELEASED. (MAIN SWITCH TURNS
OFF).
WHEN THIS OCCURS, THE IGNITION SWITCH MUST BE TURNED OFF ONCE BEFORE THE MAI\
N SWITCH WILL TURN ON.* OVER CURRENT TO TRANSISTER DRIVING MOTOR AND/OR MAGNETIC CLUTCH.
* WHEN CURRENT CONTINUED TO FLOW TO THE MOTOR INSIDE THE ACTUATOR IN THE THROTTLE VALVE ªOPENº DIRECTION.
* OPEN CIRCUIT IN MAGNETIC CLUTCH.
* MOMENTARY INTERRUPTION OF VEHICLE SPEED SIGNAL.
* SHORT CIRCUIT IN CRUISE CONTROL SWITCH.
* MOTOR DOES NOT OPERATE DESPITE THE MOTOR DRIVE SIGNAL BEING OUTPUT.
B) IF ANY OF THE FOLLOWING CONDITIONS OCCURS DURING CRUISE CONTROL OPERATION, THE SET SPEED IS ERASED AND
THE CRUISE CONTROL IS RELEASED. (THE POWER OF MAGNETIC CLUTCH IS CUT OFF U\
NTIL THE SET SWITCH IS ªONº AGAIN.) * WHEN THE VEHICLE SPEED FALLS BELOW THE MINIMUM SPEED LIMIT, APPROX. 40 KM/H ( 2.5 MPH)
* WHEN THE VEHICLE SPEED FALLS MORE THAN 16 KM/H ( 10 MPH) BELOW THE SET SPEED, E.G. ON AN UPWARD SLOPE.
* WHEN POWER TO THE CRUISE CONTROL SYSTEM IS MOMENTARILY CUT OFF.
C) IF ANY OF THE FOLLOWING CONDITIONS OCCURS DURING CRUISE CONTROL OPERATION, THE CRUISE CONTROL IS
RELEASED.
* OPEN CIRCUIT FOR TERMINAL 1 OF CRUISE CONTROL ECU AND SPLICE POINT ªI 9º.
8. AUTOMATIC TRANSMISSION CONTROL FUNCTION
*IN OVERDRIVE. IF THE VEHICLE SPEED BECOMES LOWER THAN THE OVERDRIVE CUT SPEED (SET SPEED MINUS APPROX. 4
KM/H, 2.5 MPH) DURING CRUISE CONTROL OPERATION, SUCH AS DRIVING UP A HILL, THE OVERDRIVE IS RELEASED AND THE
POWER INCREASED TO PREVENT A REDUCTION IN VEHICLE SPEED.
* AFTER RELEASING THE OVERDRIVE, VEHICLE SPEED BECOMES HIGHER THAN THE OVE\
RDRIVE RETURN SPEED (SET SPEED
MINUS APPROX. 2 M/H, 1.2 MPH) AND THE ECU JUDGES BY THE SIGNALS FROM POTENTIOMETER OF THE ACTUATOR THAT THE
UPWARD SLOPE HAS FINISHED, OVERDRIVE IS RESUMED AFTER APPROXIMATELY 6 SECONDS.
* DURING CRUISE CONTROL DRIVING, THE CRUISE CONTROL OPERATION SIGNAL IS OUTPUT FROM THE CRUISE CONTROL
ECU TO THE ENGINE AND TRANSMISSION ECU. UPON RECEIVING THIS SIGNAL, THE ENGIN\
E AND TRANSMISSION ECU
CHANGES THE SHIFT PATTERN TO NORMAL.
TO MAINTAIN SMOOTH CRUISE CONTROL OPERATION (ON A DOWNWARD SLOPE ETC.), LOCK±UP RELEASE OF THE
TRANSMISSION WHEN THE IDLING POINT OF THE THROTTLE POSITION IS ªONº IS FORBIDD\
EN.
C 8 CRUISE CONTROL ACTUATOR
1±3 : APPROX. 2K

5±4 : APPROX. 38.5

C15 CRUISE CONTROL SW [COMB. SW]
15±6 :CONTINUITY WITH MAIN SW ON
5±6 :APPROX. 420
WITH CANCEL SW ON
APPROX. 70
WITH RESUME/ACCEL SW ON
APPROX. 200
WITH SET/COAST SW ON
C19 CRUISE CONTROL ECU
14±GROUND : APPROX. 12 VOLTS WITH IGNITION SW AT ON POSITION
1, 15±GROUND : ALWAYS APPROX. 12 VOLTS
3±GROUND : CONTINUITY WITH PARKING BRAKE LEVER PULLED UP (ONE OF THE CANCEL SW) OR BRAKE LEVER WARNING SW ON
20±GROUND : 1 PULSE WITH 40CM (DRIVER VEHICLE SLOWLY)
18±GROUND : APPROX. 420
WITH CANCEL SW ON IN CONTROL SW
APPROX. 200
WITH SET/COAST SW ON IN CONTROL SW
APPROX. 70
WITH RESUME/ACCEL SW ON IN CONTROL SW
13±GROUND : ALWAYS CONTINUITY
SERVICE HINTS
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130
ECT AND A/T INDICATOR
THIS SYSTEM, ELECTRICALLY CONTROLS THE LINE PRESSURE, THROTTLE PRESSURE, LOCK±UP PRESSURE AND\
ACCUMULATOR
PRESSURE ETC. THROUGH THE SOLENOID VALVE. THE ECT IS A SYSTEM WHICH PRECISELY CONTROLS GEAR SHIFT TIMING AND
LOCK±UP TIMING IN RESPONSE TO THE VEHICLE'S DRIVING CONDITIONS AND THE ENGINE OPERATING CONDITIONS DETECTED
BY VARIOUS SENSORS, MAKING SMOOTH DRIVING POSSIBLE BY SHIFT SELECTION FOR EA\
CH GEAR WHICH IS THE MOST
APPROPRIATE TO THE DRIVING CONDITIONS AT THAT TIME, AND CONTROLS THE ENGINE TORQUE DURING SHIFTING TO ACHIEVE
OPTIMUM SHIFT FEELING.
1. GEAR SHIFT OPERATION
WHEN DRIVING, THE ENGINE WARM UP CONDITION IS INPUT AS A SIGNAL TO TERMINAL (B)44 OF THE ECU FROM THE EFI WATER
TEMP. SENSOR AND THE VEHICLE SPEED SIGNAL FROM SPEED SENSOR NO.2 IS INPUT TO TERMINAL (B)23 OF THE ECU. AT THE
SAME TIME, THE THROTTLE VALVE OPENING SIGNAL FROM THE THROTTLE POSITION SENSOR (MAIN) IS INPUT TO TERMINAL
(B)43 OF THE ECU AS ENGINE RPM CONDITION (IDLING, HIGH LOAD AND ACCELERATION CONDITIONS) SIGNAL.
BASED ON THESE SIGNALS, THE ECU SELECTS THE BEST SHIFT POSITION FOR DRIVING C\
ONDITIONS AND SENDS CURRENT TO
THE ECT SOLENOIDS.
WHEN SHIFTING TO 1ST SPEED, THE CURRENT FLOWS FROM TERMINAL (B)10 OF THE ECU " TERMINAL 1 OF ECT SOLENOIDS "
GROUND AND CONTINUITY TO NO.1 SOLENOID CAUSES THE SHIFT (NO.2 SOLENOID DOES NOT HAVE CONTINUITY AT THIS TIME).
FOR 2ND SPEED, THE CURRENT FLOWS SIMULTANEOUSLY FROM TERMINAL (B)9 OF THE ECU " TERMINAL 2 OF ECT SOLENOIDS
" GROUND, AND FROM TERMINAL (B)10 OF THE ECU " TERMINAL 1 OF ECT SOLENOIDS " GROUND, AND CONTINUITY TO NO.1
AND NO.2 SOLENOIDS CAUSES THE SHIFT.
FOR 3RD SPEED, THERE IS NO CONTINUITY TO NO.1 SOLENOID, ONLY TO NO.2 SOLENOID, CAUSING THE SHIFT.
SHIFTING INTO THE 4TH SPEED (OVERDRIVE) OCCURS WHEN NO CURRENT FLOWS TO NO.1 AND NO.2 SOLENOIDS. THE NO.4
SOLENOID (FOR ACCUMULATOR BACK PRESSURE MODULATION) IS INSTALLED TO ADJUST THE BACK PRESSURE ON THE
ACCUMULATOR AND CONTROL THE HYDRAULIC PRESSURE DURING SHIFTING AND LOCK±UP IN \
ORDER TO PROVIDE SMOOTH
SHIFTING WITH LITTLE SHIFT SHOCK.
2. LOCK±UP OPERATION
WHEN THE ECT ECU DECIDES, BASED ON EACH SIGNAL, THAT THE LOCK±UP CONDITION HAS BEEN MET, THE CURRENT FLOWS
FROM " TERMINAL (B)8 OF THE ECU " TERMINAL 3 OF THE ECT SOLENOID " GROUND, CAUSING CONTINUITY TO THE LOCK±UP
SOLENOID AND CAUSING LOCK±UP OPERATION.
3. STOP LIGHT SW CIRCUIT
IF THE BRAKE PEDAL IS DEPRESSED (STOP LIGHT SW ON) WHEN DRIVING IN LOCK±UP CONDITION, A SIGNAL IS INPUT\
TO
TERMINAL (A)4 OF THE ECU. THE ECU OPERATES AND CUTS THE CURRENT TO THE SOLENOID TO RELEASE LOCK±UP.
4. OVERDRIVE CIRCUIT
*O/D MAIN SW ON
WHEN THE O/D MAIN SW IS TURNED ON (SW POINT IS OPEN), A SIGNAL IS INPU\
T TO TERMINAL (A)28 OF THE ECU AND THE ECT
CAUSES SHIFT TO OVERDRIVE WHEN THE CONDITIONS FOR OVERDRIVE ARE MET.
* O/D MAIN SW OFF
WHEN THE O/D MAIN SW IS TURNED OFF (SW POINT IS CLOSED), THE CURRENT FLOWI\
NG THROUGH THE O/D OFF INDICATOR
LIGHT FLOWS TO GROUND BY WAY OF THE O/D MAIN SW AND CAUSES THE O/D OFF INDICATOR LIGHT TO LIGHT UP. AT THE
SAME TIME, A SIGNAL IS INPUT TO TERMINAL (A)28 OF THE ECU AND THE ECT PREVENTS SHIFT INTO OVERDRIVE.
5. ECT PATTERN SELECT SW CIRCUIT
WHEN THE ECT PATTERN SELECT SW IS CHANGED FROM ªNORMALº TO ªPOWERº, THE CURRENT THROUGH THE GAUGE FUSE
FLOWS TO TERMINAL 4 OF ECT PATTERN SELECT SW " TERMINAL 3 " TERMINAL (B)4 OF A/T INDICATOR " TERMINAL (C)23 "
GROUND AND CAUSES THE INDICATOR LIGHT TO LIGHT UP. AT THE SAME TIME, THE CURRENT FLOWS TO TERMINAL (A)18 OF
THE ECU AND THE ECU PERFORMS SHIFT UP AND SHIFT DOWN AT A HIGHER VEHICLE SPEED RANGE COMPARED WITH
ªNORMALº POSITION.
6. KICK DOWN OPERATION
WHEN THE ACCELERATOR IS DEPRESSED FURTHER THAN THE FULL THROTTLE POSITION WHILE DRIVING, THE KICK DOWN SW
TURNS ON AND ITS SIGNAL IS INPUT TO TERMINAL (A)3 OF THE ECU. THEN, THE ECU CONTROLS THE CURRENT WHICH FLOWS
FROM TERMINALS (B)10 AND (B)9 OF THE ECU TO THE NO. 1 AND NO. 2 SOLENOIDS AND SHIFTS DOWN BY TURNING THE
SOLENOIDS ON AND OFF.
7. CRUISE CONTROL
WHEN CRUISE CONTROL OPERATION IS SELECTED A SIGNAL IS INPUT TO TERMINAL (A)12 OF THE ECU FROM CRUISE CONTROL
ECU. AS A RESULT, THE ECU OPERATES AND CONTROLS OVERDRIVE, LOCK±UP AND SO ON FOR SMOOTH DRIVING.
SYSTEM OUTLINE
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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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METER, ANALOGCurrent flow activates a magnetic
coil which causes a needle to
move, thereby providing a relative
display against a background
calibration.
LED (LIGHT EMITTING DIODE)
Upon current flow, these diodes
emit light without producing the
heat of a comparable light.
IGNITION COIL
Converts low±voltage DC current
into high±voltage ignition current
for firing the spark plugs.
1. SINGLE
FILAMENT
GROUND
The point at which wiring attaches
to the Body, thereby providing a
return path for an electrical circuit;
without a ground, current cannot
flow. Current flow causes a headlight
filament to heat up and emit light.
A headlight may have either a
single (1) filament or a double (2)
filament.
BATTERY
Stores chemical energy and
converts it into electrical energy.
Provides DC current for the auto's
various electrical circuits.
CAPACITOR (Condenser) A small holding unit for temporary
storage of electrical voltage.
CIRCUIT BREAKER Basically a reusable fuse, a circuit
breaker will heat and open if too
much current flows through it. Some
units automatically reset when cool,
others must be manually reset.
DIODE A semiconductor which allows
current flow in only one direction.
DIODE, ZENER A diode which allows current flow
in one direction but blocks reverse
flow only up to a specific voltage.
Above that potential, it passes the
excess voltage. This acts as a
simple voltage regulator.
FUSE A thin metal strip which burns
through when too much current
flows through it, thereby stopping
current flow and protecting a
circuit from damage.
FUSIBLE LINK A heavy±gauge wire placed in
high amperage circuits which
burns through on overloads,
thereby protecting the circuit.
The numbers indicate the cross±
section surface area of the wires. HORN
An electric device which sounds a
loud audible signal.
LIGHT Current flow through a filament
causes the filament to heat up
and emit light.
METER, DIGITAL Current flow activates one or
many LED's, LCD's, or fluorescent
displays, which provide a relative
or digital display.
MOTOR A power unit which converts
electrical energy into mechanical
energy, especially rotary motion.
CIGARETTE LIGHTER
An electric resistance heating
element.
DISTRIBUTOR, IIA Channels high±voltage current
from the ignition coil to the
individual spark plugs. 2. DOUBLE
FILAMENT
HEADLIGHTS
FUEL
(for High Current Fuse or
Fusible Link)
(for Medium Current Fuse)
M
16
GLOSSARY OF TERMS AND SYMBOLS
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* The system shown here is an EXAMPLE ONLY. It is different to the actual circuit shown in the SYSTEM CIRCUITS SECTION.
GROUND POINT
9
The ground points circuit diagram shows the connections from all major p\
arts to the respective ground points. When
troubleshooting a faulty ground point, checking the system circuits which use a common ground may help you iden\
tify the
problem ground quickly. The relationship between ground points ( , , and shown below) can also be
checked this way.
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