warning light LEXUS SC400 1991 Service Manual PDF

Engine & ECT ECU
TERMINALS OF ENGINE & ECT ECU
TerminalNo.SymbolConnectionTerminalNo.SymbolConnection
E9 ± 1IGSWIgnition SwitchE9 ± 31+ BEFI Main Relay
2SPDNo. 1 Speed Sensor32+ B1EFI Main Relay
3KDKick±Down Switch33BATTBattery
4STPStop light Switch34A/CA/C Control Assembly
5±35±
6WªCHECKº Engine Warning Light36±
7RNeutral Start Switch37TRTRAC ECU
8±38NEOTRAC ECU
92Neutral Start Switch39VTO2TRAC ECU
10LNeutral Start Switch40VTO1TRAC ECU
11ADCC ECUE10 ± 1NCO T/M Input Speed Sensor
12OD1CC ECU2±
13±3SP2No. 2 Speed Sensor for ECT
14±4E11ECU Ground
15±5G2Cam position Sensor
16±6G1Cam position Sensor
17TTTDCL7NFEngine Speed Sensor
18PECT Pattern Select Switch8±
19TE2Check Connector9S2ECT Solenoid Value
20TE1Check Connector10S1ECT Solenoid Value
21D1Fuel Pump ECU11±
22FPCFuel Pump ECU12±
23ACMGA/C Magnet Clutch Relay13SLN
No.3 ECT Solenoid Valve
24M±RELEFI Main Relay14SLUNo.4 ECT Solenoid Valve
25±15±
26±16±
27±17#10No.3 and No.5 Injectors
28OD2O/D Main Relay18#20No.4 and No.6 Injectors
29±19#20No.2 and No.8 Injectors
30±20#40No.1 and No.7 Injectors
Engine & ECT ECU Terminals
FI±126 ± Electronic Control \
System (Engine & ECT ECU)EFI SYSTEM
WhereEverybodyKnowsYourName

The EFI system is composed of three basic sub±systems: Fuel, Air Induction and Elect\
ronic Control
Systems.
FUEL SYSTEM
An electric pump fuel pressure supplies sufficient fuel, under a constant pressure, to the EFI injectors. In
accordance with signals from the ECU (Electronic Control Unit), these \
injectors inject the quantity of fuel most
appropriate for the engine condition into the intake manifold.
AIR INDUCTION SYSTEM
The air induction system provides sufficient air for engine operation.
ELECTRONIC CONTROL SYSTEM
The 1UZ±FE engine (ECU±formerly EFI computer) with a microcomputer \
centrally controls the EFI, ESA,
ISC and Diagnosis system, etc. The ECU controls the following functions:
1. Electronic Fuel Injection (EFI)
The ECU receives signals from various sensors indicating changing engine op\
eration conditions such as:Intake air volume
Intake air temperature
Coolant temperature
Engine rpm
Acceleration/deceleration
Exhaust oxygen content etc.
The signals are utilized by the ECU to determine the injection duration nec\
essary for an optimum air±fuel
ratio.
2. Electronic Spark Advance (ESA) The ECU is programmed with data for optimum ignition timing under any and all opera\
ting conditions. Using
data provided by sensors which monitor various engine functions (rpm, coola\
nt temperature, etc.), the
Electronic Control Unit (ECU) triggers the spark at precisely right instant. (S\
ee IG section)
3. Idle Speed Control (ISC) The ECU is programmed with idle speed data for various engine conditions (\
coolant temperature, air condi-
tioner ON/OFF, etc.).
The air volume flowing through the throttle valve by±pass passage is adj\
usted according to the signal from
each sensor and the idle speed is kept at the set value.
4. Diagnosis Function When the ECU detects any malfunctions or abnormalities in the sensor network\
, it lights the ºCHECKº en-
gine warning light in the combination meter. At the same time, the trouble is identified and a diagnostic code
is recorded by the ECU. The diagnostic code can be read by the number of\
blinks of the ºCHECKº engine
warning light when terminals TE1 and E1 are connected. The diagnostic co\
des are refer to the later page.
(See TR section)
5. Self±Correction Function If any sensor malfunctions, an average value recorded in the back±up ci\
rcuit is substituted to make driving
possible.
If danger is predicted, the engine is stopped and the ºCHECKº engine\
warning light will light up.
6. Fail±Safe Function Even if an abnormality occurs in the ECU, the back±up circuit uses a specifie\
d fuel injection and ignition
timing to provide vehicle driveability, and also lightsup the ºCHECKº engine warning light.
FI±4
EFI SYSTEM
± Description
WhereEverybodyKnowsYourName

GENERAL MAINTENANCE
MA00M±03
There are the maintenance and inspection
items which are considered to be the owner's
responsibility. They can be performed by the
owner or be can have them done at a service
shop. These items include those which should
be checked on a daily basis, those which, in
most cases, do not require (special) tools and
those which are considered to be reasonable
for the owner to perform. Items and procedures
for general maintanance are as follows:
MA00P±04
OUTSIDE VEHICLE
1. TIRES
(a) Check the pressure with a gauge. Adjust ifnecessary.
(b) Check for cuts, damage or excessive wear.
2. WHEEL NUTS Wheel checking the tires, check the nuts for
looseness or for missing nuts. If necessary,
tighten them.
3. TIRE ROTATION It is recommended that tires be rotated every
12,000 km (7,500 miles).
4. WINDSHIELD WIPER BLADES Check for wear or cracks whenever they do not
wipe clean. Replace if necessary.
5. FLUID LEAKS
(a) Check underneath for leaking fuel, oil, water or
other fluid.
(b) If you smell gasoline fumes or notice any leak, have the cause found and corrected.
6. DOORS AND ENGINE HOOD
(a) Check that all doors including the trunk lid operate smoothly, and that all latches lock
securely.
(b) Check that the engine hood secondary latch secures the hood from opening when the
primary latch is released.
MA00R±05
INSIDE VEHICLE
7. LIGHTS
(a) C h e c k t h a t t h e h eadlights, stop lights,
tail±lights, turn signal lights, and other lights
are all working. (b) Check the headlight aiming.
8. WARNING LIGHT AND BUZZERS
Check that all warning lights and buzzers func-
tion properly.
9. HORN Check that it is working.
10. WINDSHIELD GLASS
Check for scratches, pits or abrasions.
11. WINDSHIELD WIPER AND WASHER
(a) Check operation of the wipers and washer.
(b) Check that the wipers do not streak.
12. WINDSHIELD DEFROSTER Check that the air comes out from the defroster
outlet when operating the heater air condition-
er at defroster mode.
13. REAR VIEW MIRROR
Check that it is mounted securely.
14. SUN VISORS Check that they move freely and are mounted
securely.
15. STEERING WHEEL Check that it has the specified freeplay. Be
alert for changes in steering condition, such as
hard steering, excessive freeplay or strange
noise.
16. SEATS
(a) Check that all front seat controls such as seat adjusters, seatback recliner, etc. operate
smoothly.
(b) Check that all latches lock securely in any position.
(c) Check that the locks hold securely in any latched position.
(d) Check that the head restraints move up and
down smoothly and that the locks hold securely
in ay latches position.
(e) For folding±down rear seat backs, check that the latches lock securely.
17. SEAT BELTS
(a) Ch e ck th a t th e se a t be lt syste m su ch as buckles, retractors and anchors operate
properly and smoothly.
(b) Check that the belt webbing is not cut, frayed,
worn or damaged.
18. ACCELERATOR PEDAL Check the pedal for smooth operation and un-
even pedal effort or catching.
±
MAINTENANCE (1UZ ± FE)MA±19
WhereEverybodyKnowsYourName

The EFI system is composed of three basic sub±systems: Fuel, Air Induction and Elect\
ronic Control
Systems.
FUEL SYSTEM
An electric pump fuel pressure supplies sufficient fuel, under a constant pressure, to the EFI injectors. In
accordance with signals from the ECU (Electronic Control Unit), these \
injectors inject the quantity of fuel most
appropriate for the engine condition into the intake manifold.
AIR INDUCTION SYSTEM
The air induction system provides sufficient air for engine operation.
ELECTRONIC CONTROL SYSTEM
The 1UZ±FE engine (ECU±formerly EFI computer) with a microcomputer \
centrally controls the EFI, ESA,
ISC and Diagnosis system, etc. The ECU controls the following functions:
1. Electronic Fuel Injection (EFI)
The ECU receives signals from various sensors indicating changing engine op\
eration conditions such as:Intake air volume
Intake air temperature
Coolant temperature
Engine rpm
Acceleration/deceleration
Exhaust oxygen content etc.
The signals are utilized by the ECU to determine the injection duration nec\
essary for an optimum air±fuel
ratio.
2. Electronic Spark Advance (ESA) The ECU is programmed with data for optimum ignition timing under any and all opera\
ting conditions. Using
data provided by sensors which monitor various engine functions (rpm, coola\
nt temperature, etc.), the
Electronic Control Unit (ECU) triggers the spark at precisely right instant. (S\
ee IG section)
3. Idle Speed Control (ISC) The ECU is programmed with idle speed data for various engine conditions (\
coolant temperature, air condi-
tioner ON/OFF, etc.).
The air volume flowing through the throttle valve by±pass passage is adj\
usted according to the signal from
each sensor and the idle speed is kept at the set value.
4. Diagnosis Function When the ECU detects any malfunctions or abnormalities in the sensor network\
, it lights the ºCHECKº en-
gine warning light in the combination meter. At the same time, the trouble is identified and a diagnostic code
is recorded by the ECU. The diagnostic code can be read by the number of\
blinks of the ºCHECKº engine
warning light when terminals TE1 and E1 are connected. The diagnostic co\
des are refer to the later page.
(See TR section)
5. Self±Correction Function If any sensor malfunctions, an average value recorded in the back±up ci\
rcuit is substituted to make driving
possible.
If danger is predicted, the engine is stopped and the ºCHECKº engine\
warning light will light up.
6. Fail±Safe Function Even if an abnormality occurs in the ECU, the back±up circuit uses a specifie\
d fuel injection and ignition
timing to provide vehicle driveability, and also lightsup the ºCHECKº engine warning light.
FI±4
EFI SYSTEM
± Description
WhereEverybodyKnowsYourName

Engine & ECT ECU
TERMINALS OF ENGINE & ECT ECU
TerminalNo.SymbolConnectionTerminalNo.SymbolConnection
E9 ± 1IGSWIgnition SwitchE9 ± 31+ BEFI Main Relay
2SPDNo. 1 Speed Sensor32+ B1EFI Main Relay
3KDKick±Down Switch33BATTBattery
4STPStop light Switch34A/CA/C Control Assembly
5±35±
6WªCHECKº Engine Warning Light36±
7RNeutral Start Switch37TRTRAC ECU
8±38NEOTRAC ECU
92Neutral Start Switch39VTO2TRAC ECU
10LNeutral Start Switch40VTO1TRAC ECU
11ADCC ECUE10 ± 1NCO T/M Input Speed Sensor
12OD1CC ECU2±
13±3SP2No. 2 Speed Sensor for ECT
14±4E11ECU Ground
15±5G2Cam position Sensor
16±6G1Cam position Sensor
17TTTDCL7NFEngine Speed Sensor
18PECT Pattern Select Switch8±
19TE2Check Connector9S2ECT Solenoid Value
20TE1Check Connector10S1ECT Solenoid Value
21D1Fuel Pump ECU11±
22FPCFuel Pump ECU12±
23ACMGA/C Magnet Clutch Relay13SLN
No.3 ECT Solenoid Valve
24M±RELEFI Main Relay14SLUNo.4 ECT Solenoid Valve
25±15±
26±16±
27±17#10No.3 and No.5 Injectors
28OD2O/D Main Relay18#20No.4 and No.6 Injectors
29±19#20No.2 and No.8 Injectors
30±20#40No.1 and No.7 Injectors
Engine & ECT ECU Terminals
FI±126 ± Electronic Control \
System (Engine & ECT ECU)EFI SYSTEM
WhereEverybodyKnowsYourName

DIAGNOSIS SYSTEM
DESCRIPTION
The ECU contains a built±in self±diagnosis system by which
troubles with the engine signal network are detected and a
ºCHECKº engine warning light on the instrument panel lights up.
By analyzing various signals as shown in the later table (See page
TR±14) the Electronic Control Unit (ECU) detects system malfunc-
tions relating to the sensors or actuators.
In the normal mode, the self±diagnosis system monitors 22 (USA
specification vehicles with TRAC control) or 21 (USA (except for
California) and Canadian specification vehicles with TRAC con-
trol) items, indicated by code No. as shown in TR±14. A ºCHECKº
engine warning light informs the driver that a malfunction has been
detected. The light goes off automatically when the malfunction
has been repaired. But the diagnostic code(s) remains stored in
the ECU memory (except for code Nos. 16 and 53). The ECU
stores the code(s) until it is cleared by removing the EFI fuse with
the ignition switch off.
The diagnostic code can be read by the number of blinks of the
ºCHECKº engine warning light when TE1 and E1 terminals on the
TDCL or check connector are connected. When 2 or more codes
are indicated, the lowest number (code) will appear first.
In the test mode, 15 (USA specification vehicles with TRAC con-
trol) or 14 (USA (except for California) and Canadian specification
vehicles with TRAC control) items, indicated by code No. as
shown in TR±14 are monitored. If a malfunction is detected in any
one of the systems indicated by code Nos. 13, 21, 22, 24, 25, 26,
27, 28, 29, 35, 41, 42, 47, 71 and 78 (USA specification vehicles)
or 13, 21, 22, 24, 25, 26, 27, 28, 29, 35, 41, 42, 47 and 78 (USA
(except for California) and Canadian specification vehicles) the
ECU lights the ºCHECKº engine warning light to warn the techni-
cian that malfunction has been detected. In this case, TE2 and E1
terminals on the TDCL should be connected as shown later. (See
page TR±12 ).
In the test mode, even if the malfunction is corrected, the malfunc-
tion code is stored in the ECU memory even when the ignition
switch is off (except code Nos. 43 and 51). This also applies in the
normal mode. The diagnostic mode (normal or test) and the output
of the ºCHECKº engine warning light can be selected by connect-
ing the TE1, TE2 and E1 terminals on the check connector or
TDCL, as shown later.
A test mode function has been added to the functions of the self±
diagnosis system of the normal mode for the purpose of detecting
malfunctions such as poor contact, which are difficult to detect in
the normal mode. This function fills up the selfdiagnosis system.
The test mode can be implemented by the technician following the
appropriate procedures of check terminal connection and opera-
tion described later. (See page TR±12)
TR±10
±
ENGINE TROUBLESHOOTING Diagnosis System
WhereEverybodyKnowsYourName

Diagnosis Inspection (Normal Mode)
ºCHECKº ENGINE WARNING LIGHT
CHECK
1. The ºCHECKº engine warning light will come on when theignition switch is turned ON and the engine is not running.
HINT: If the ºCHECKº engine warning light does not light up,
proceed to troubleshooting of the combination meter (See
page
BE±146).
2. When the engine is started, the ºCHECKº engine warning light should go off.
If the light remains on, the diagnosis system has detected a
malfunction or abnormality in the system.
DIAGNOSTIC CODE CHECK
1. Turn ignition switch on.
2. Using SST, connect terminals between TE1 and E1 of TDCLor check connector.
SST 09843±18020
3. Read the diagnostic code from ºCHECKº engine warning light.
HINT: If a diagnostic code is not output, check the TE1 termi-
nal circuit (See page TR±146).
As an example, the blinking patterns for codes;normal, 12
and 31 are as shown on the illustration.
4. Check the details of the malfunction using the diagnostic
code table on page TR±14.
5. After completing the check, disconnect terminals TE1 and E1, and turn off the display.
HINT: In the event of 2 or more malfunction codes, indication
will begin from the smaller numbered code and continue in
order to the larger.
±
ENGINE TROUBLESHOOTING Diagnosis SystemTR±11
WhereEverybodyKnowsYourName

Diagnosis Inspection (Test Mode)
Compared to the normal mode, the test mode has high sensing
ability to detect malfunctions.
It can also detect malfunctions in the starter signal circuit, the IDL
contact signal of the throttle position sensor, air conditioner signal
and neutral start switch signal.
Furthermore, the same diagnostic items which are detected in the
normal mode can also be detected in the test mode.
DIAGNOSTIC CODE CHECK
1. Initial conditions.(a) Battery voltage 11 V or more.
(b) Throttle valve fully closed (throttle position sensor IDLpoints closed).
(c) Transmission in neutral position.
(d) Air conditioner switched off.
2. Turn ignition switch off.
3. Using SST, connect terminals TE2 and E1 of TDCL. SST 09843±18020
4. Turn ignition switch on. HINT:
wTo confirm that the test mode is operating, check that the
ºCHECKº engine warning light flashes when the ignition
switch is turned to ON.
w If the ºCHECKº engine warning light does not flash,
proceed to tro ubleshooting of the TE2 terminal circuit on
page TR±146 .
5. Start the engine.
6. Simulate the conditions of the malfunction described by the customer.
7. After the road test, using SST, connect terminals TE1 and E1
of TDCL or check connector.
SST 09843±18020
8. Read the diagnostic code on ºCHECKº engine warning light on the combination meter (See page TR±11).
9. After completing the check, disconnect terminals TE1, TE2 and E1, and turn off the display.
HINT:
wThe test mode will not start if terminals TE2 and E1 are
connected after the ignition switch is turned on.
w When the engine is not cranked, diag. codes º43º
(Starter signal) output, but this is not abnormal.
w When the automatic transmission shift lever is in the ºDº,
º2º, ºLº or ºRº shift position, or when the air conditioner
is on or when the accelerator pedal is depressed, code
º51º (Switch condition signal) is output, but this is not
abnormal.
TR±12
±
ENGINE TROUBLESHOOTING Diagnosis System
WhereEverybodyKnowsYourName

DIAGNOSTIC CODE CLEARANCE
1. After repair of the trouble areas, the diagnostic code retainedin the ECU memory must be cleared out by removing the EFI
fuse (30A) from R/B No. 2 for 10 seconds or more, with the
ignition switch OFF.
HINT:
wCancellation can also be done by removing the battery
negative (±) terminal, but in this case, other memory
systems (clock, etc.) will also be cancelled out.
w If it is necessary to work on engine components
requiring removal of the battery terminal, a check must
first be made to see if a diagnostic code has been
recorded.
2. After cancellation, road test the vehicle to check that a normal
code is now read on the ºCHECKº engine warning light.
If the same diagnostic code appears, it indicates that the
trouble area has not been repaired thoroughly.
±
ENGINE TROUBLESHOOTING Diagnosis SystemTR±13
WhereEverybodyKnowsYourName

If a malfunction code is displayed during the diagnostic code check in tes\
t mode, check the circuit for that code
listed in the table below (Proceed to the page given for that circuit).
Tro ble Area
ºCHECKº EngineWarning Light *
Memory*See Page
Trouble AreaNormal
ModeTest
Mode
±±±±±±±±±±±±±±±±±±±±±±±±±±±±±
w Open or short in engine speed sensor, No. 1, No. 2
cam position sensor circuit.
w Engine speed sensor
w No. 1, No. 2 cam position sensor
w Starter
w ECU
ONN.A.TR±48
w Open or short in engine speed sensor circuit.w Oen or short in engine s eed sensor circuit.
w Engine speed sensor
ONN.A. Engine s eed sensor
w ECU
ONN.A.
w Open or short in engine speed sensor circuit.g
w Mechanical system malfunction (skipping teeth of
ti itiming
wbelt belt stretched)N.A.ONTR 52wbelt, belt stretched)
wEngine speed sensor
TR±52
w Engine s eed sensor
w ECU
w Mechanical system malfunction (skipping teeth ofw Mechanical system malfunction (ski ing teeth of
wtiming belt, belt stretched)ONNAwtiming belt, belt stretched)
w No. 1, No. 2 cam position sensorONN.A. No. 1, No. 2 cam osition sensor
w ECU
w Open or short in IGF1 circuit from igniter No.
1±ECU.
w Igniter No. 1
w ECU
ONN.A.TR±54
w Open or short in IGF2 circuit from igniter No.
2±ECU.
w Igniter No. 2
w ECU
ONN.A.TR±54
w ECUONN.A.XTR±61
w Open or short in heater circuit of main oxygen sen-
sor.
w Main oxygen sensor heaterONN.A.w Main oxygen sensor heater
w ECU
TR±62
w Main oxygen sensor circuit
w
Main oxygen sensorONONw Main oxygen sensor
*1, 2: See page TR±20.
±
ENGINE TROUBLESHOOTING Diagnostic Code ChartTR±15
WhereEverybodyKnowsYourName