warning light LEXUS SC400 1991 Service Manual Online

ºCHECKº Engine
Tro ble Area
CHECK Engine
Warning Light *
Memory*See PageTrouble AreaNormal
ModeTest
ModeMemory* See Page
w Open or short in water temp. sensor circuit.
w Water temp. sensor
w ECU
ONONTR±68
w Open or short in intake air tempsensor circuitOFFw Open or short in intake air temp. sensor circuit.
w Intake air tempsensor
OFF
ONTR 72w Intake air temp. sensor
ECUON*3
ONTR±72
w ECUON*3
w Open or short in main oxygen sensor circuit.w Oen or short in main oxygen sensor circuit.
w Main oxygen sensor
Main oxygen sensor
w Ignition systemgy
w Water temp. sensor
w Open or short in injector circuit.w Oen or short in injector circuit.
w Fuel line pressure
(injector blockage)w Fuel line ressure (injector blockage)
w Air flow meter (air intake)ONONTR±74 Air flow meter (air intake)
w Engine ground bolt loose

gg
w Foreign object caught in valve
w Fuel line pressure (injector leak, blockage)w Fuel line ressure (injector leak, blockage)
w Mechanical system malfunction Mechanical system malfunction
w(skipping teeth of timing belt)(g g)
w Ignition system
w Open or short in heater circuit of sub±oxygen sen-
sor.
w Sub±oxygen sensor heaterONN.A.w Sub±oxygen sensor heater.
w ECU
TR±82
w Open or short in sub±oxygen sensor circuit.
TR 82
w Oen or short in sub oxygen sensor circuit.
w Sub±oxygen sensor
ONON Sub oxygen sensor
w ECU
w Same as (1) of Code No. 21ONN.A.
TR 62w Same as (2) of Code No. 21ONONTR±62
w Same as (1) of Code No. 27ONN.A.
TR 82w Same as (2) of Code No. 27ONONTR±82
*1, 2, 3: See page TR±20.
±
ENGINE TROUBLESHOOTING Diagnostic Code ChartTR±17
WhereEverybodyKnowsYourName

Trouble Area
ºCHECKº
Engine Warning
Light *

Memory* See PageTrouble Area
Normal
ModeTest
Mode
MemorySee Page
w Open or short in air flow meter circuit.
w Air flow meter
w ECU
ONN.A.TR±88
wECUONONTR±92
wOpen or short in throttle position sensor circuit.
wThrottle position sensorONONTR±94Throttle osition sensor
w ECU
wNo. 1 speed sensor
w Combination meter
w Open or short in No. 1 speed sensor circuit.
w ECU
ONONTR±98
wOpen or short in starter signal circuit.
w Open or short in ignition switch or main relay circuit.
w ECU
N.A.OFFXTR±100
wOpen or short in sub±throttle position sensor circuit.
wSub±throttle position sensorOFFONTR±94Sub throttle osition sensor
wECU
wOpen or short in No. 1 knock sensor circuit.wOen or short in No. 1 knock sensor circuit.
w No. 1 knock sensor (looseness)
ONN.A.No. 1 knock sensor (looseness)
wECU

w ECUONN.A.XTR±102
w Open or short in No. 2 knock sensor circuit.w Oen or short in No. 2 knock sensor circuit.
w No. 2 knock sensor (looseness)
ONN.A. No. 2 knock sensor (looseness)
w ECU

*1, 2: See page TR±20.
±
ENGINE TROUBLESHOOTING Diagnostic Code ChartTR±19
WhereEverybodyKnowsYourName

DIAGNOSTIC CODE CHART (Cont'd)
*1: ºONº displayed in the diagnosis mode column indicates that the º\
CHECKº Engine Warning Light islighted up when a malfunction is detected. ºOFFº indicates that the ºC\
HECKº does not light up during
malfunction diagnosis, even if a malfunction is detected. ºN.A.º i\
ndicates that the item is not included
in malfunction diagnosis.
*2: ºOº in the memory column indicates that a diagnostic code is reco\
rded in the ECU memory when a mal- function occurs. ºXº indicates that a diagnostic code is not recor\
ded in the ECU memory even if a mal-
function occurs. Accordingly, output of diagnostic results in normal or test mode is performed with \
the
IG switch ON.
*3: Only for USA specification vehicles.
TR±20
±
ENGINE TROUBLESHOOTING Diagnostic Code Chart
WhereEverybodyKnowsYourName

Trouble Area
ºCHECKº
Engine Warning
Light*

Memory* See PageTrouble Area
Normal
ModeTest
Mode
MemorySee Page
w Open or short in EGR step motor circuit.ONNA Oen or short in EGR ste motor circuit.
w ECUONN.A.
w Open in EGR gas temp. sensor circuit.ONON
TR±108 Oen in EGR gas tem . sensor circuit.
w ECUONON
w Open or short in fuel pump ECU circuit.
w Fuel pump ECU
w Engine & ECT ECU power source circuit.
w Fuel pump
w Engine & ECT ECU
ONONTR±114
w A/C switch circuit
w Throttle position sensor IDL circuit
w Neutral start switch circuit.
w Accelerator pedal and cable
w ECU
N.A.OFFXTR±118
*4: This indicates items for which º2 trip detection logicº is used. With this logic, when a lo\
gic malfunction is
first detected, the malfunction is temporarily stored in the ECU memory. If the same case is detected again
during the second drive test, this second detection causes the ºCHECK\
º Engine Warning Light to light up.
The 2 trip repeats the same mode a 2nd time. (However, the IG switch must be turned OFF between the
1st trip and 2nd trip).
In the Test Mode, the ºCHECKº Engine Warning Light lights up the 1st trip a malfunction is detected.
±
ENGINE TROUBLESHOOTING Diagnostic Code ChartTR±21
WhereEverybodyKnowsYourName

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
WhereEverybodyKnowsYourName

CIRCUIT DESCRIPTION (Cont'd)
Purpose of the driving pattern.
(a) To simulate diag. code detecting condition after diag. code is recorded.
(b) To check that the malfunction is corrected when the repair is completed confirming that diag.code is no longer detected.
DIAGNOSIS CODE DETECTION DRIVING PATTERN
Initiate test mode (See page TR±12).
Start engine and warm up.
After engine is warmed up, let it idle for 3 min.
With the A/C ON and the transmission in D range (O/D ON), perform
gradual acceleration with in the range 1,300 ± 1,700 rpm (centered
around 1,500 rpm).
(Take care that the engine speed does not fall below 1,200 rpm when
shifting. Gradually depress the accelerator pedal and kept it. Steady so
that engine braking does not occur.)
Maintain the vehicle speed at 40 ± 50 mph (64 ± 80 km/h).
Keep the vehicle running for 1 ± 2 min. after starting acceleration.
HINT: If a malfunction exists, the ºCHECKº engine warning light will light\
up af-
ter approx. 60 sec. from the start of acceleration.
NOTICE: If the conditions in this test are not strictly followed, detection of the malfunction will not be possible.
TR±63
±
ENGINE TROUBLESHOOTING Circuit Inspection
WhereEverybodyKnowsYourName

CIRCUIT DESCRIPTION (Cont'd)
DIAGNOSIS CODE DETECTION DRIVING PATTERN
Purpose of the driving pattern.
(a) To simulate diag. code detecting condition after diag. code is recorded.
(b) To check that the malfunction is corrected when the repair is completed c\
onfirming that diag. code is no longer detected.
Malfunction: Open or Short in Main Oxygen Sensor

Initiate test mode (See page TR±12).
Start engine and warm up.
After engine is warmed up, let it idle for 3 min.
Perform quick racing to 4,000 rpm three times by accelerator pedal.
After performing the racing in (4), perform racing at 2,000 rpm for 90\
sec.
HINT: If a malfunction exists, the ºCHECKº engine warning light will light up after 90 sec. from the start of racing.
NOTICE: If the conditions in this test are not strictly followed, detection of t\
he malfunction will not be possible.
TR±75±
ENGINE TROUBLESHOOTING Circuit Inspection
WhereEverybodyKnowsYourName

CIRCUIT DESCRIPTION (Cont'd)
DIAGNOSIS CODE DETECTION DRIVING PATTERN
Purpose of the driving pattern.
(a) To simulate diag. code detecting condition after diag. code is recorded.
(b) To check that the malfunction is corrected when the repair is completed co\
nfirming that diag. codeis no longer detected.
Malfunction: Open or Short in Injector circuit, Injector Leak or Blockage, Loose E/G Earth Bolt.

Initiate test mode (See page TR±12).
Start engine and warm up.
After engine is warmed up, let it idle for 5 min.
(After the engine is started, do not depress the accelerator pedal.)
\bIf the malfunction is not detected during idling, perform racing without a\
ny load at approx.
2,000 rpm for 30 sec.
HINT: If a malfunction exists, the ºCHECKº engine warning light will light up during the 5 min. idling
period or within 30 sec. of starting racing.
NOTICE: If the conditions in this test are not strictly followed, detection of the\
malfunction will not be possible.
±
ENGINE TROUBLESHOOTING Circuit InspectionTR±76
WhereEverybodyKnowsYourName

CIRCUIT DESCRIPTION (Cont'd)
DIAGNOSIS CODE DETECTION DRIVING PATTERN
Purpose of the driving pattern.
(a) To simulate diag. code detecting condition after diag. code is recorded.
(b) To check that the malfunction is corrected when the repair is completed co\
nfirming that diag. codeis no longer detected.
Malfunction: Open or Short in Sub±Oxygen Sensor

Initiate test mode (See page TR±12).
Start engine and warm up.
After engine is warmed up, let it idle for 3 min.
With the A/C ON and the transmission in D range (O/D OFF), drive at 40 ±\
60 mph (64±96
km/h) for 6 min.
After the driving in , stop the vehicle.
Once the vehicle is stopped, within the next minute apply acceleration w\
ith the throttle
fully open for 4 sec.
HINT: If a malfunction exists, the ºCHECKº engine warning light will light\
up after full acceleration for 4 sec.
NOTICE: If the conditions in this test are not strictly followed, detection of the\
malfunction will not be possible.
±
ENGINE TROUBLESHOOTING Circuit InspectionTR±83
WhereEverybodyKnowsYourName

NGOK
OKNG
v
INSPECTION PROCEDURE
1Check output condition of diag. code 43.
C
OK
P
OK
C
Setting the test mode.
(2) Turn ignition switch OFF.
(2) Connect terminals TE2 and E1 of TDCL.
(2) Turn ignition switch ON.(Don't start the engine)
(2) Connect terminals TE1 and E1 of TDCL.
Check if code ª43º is output by the ªCHECKº engine
warning light.
Code ª43º is output.
Start the engine.
Check if the code ª43º disapears.
Code ª43º is not output.
Proceed to next circuit inspection shown on maxtric
chart (See page TR±35).
2Check for open in harness and connectors between engine & ECT ECU and st\
arter relay
(See page IN±27).
Repair or replace harness or connector.
Check and replace engine & ECT ECU.
±
ENGINE TROUBLESHOOTING Circuit InspectionTR±101
WhereEverybodyKnowsYourName