TOYOTA SUPRA 1986 Service Repair Manual

DTC 42 No.1 Vehicle Speed Sensor Signal Circuit
CIRCUIT DESCRIPTION
The No.1 vehicle speed sensor outputs a 4±pulse signal for every revolution of the rotor shaft, which is
rotated by the transmission output shaft via the driven gear. After this signal is converted into a more pre-
cise rectangular waveform by the waveform shaping circuit inside the odometer and trip meter, it is then
transmitted to the engine control module. The ECM determines the vehicle speed based on the frequency
of these pulse signals.
No.1 Vehicle
Speed SensorTelltale Light
RH (Odometer
and Trip Meter)
No.1 Vehicle Speed Sensor
DTC No.
Diagnostic Trouble Code Detecting ConditionTrouble Area

No.1 Vehicle speed sensor

Telltale light RH (Odometer and trip meter)

Open or short in No.1 vehicle speed sensor
circuit

ECM
For A/T
All conditions below are detected
continuously for 8 sec. or more:
(a) No.1 vehicle speed signal: 0 km/h
(mph)
(b) Engine speed: 3,000 rpm or more
(c) Park/neutral position switch: OFF
(d) Stop light switch: OFF
For A/T
All conditions below are detected
continuously for 8 sec. or more:
(a) No.1 vehicle speed signal: 0 km/h
(mph)
(b) Engine speed: Between 2,000 rpm
and 5,000 rpm
(c) Engine coolant temp.: 80°C (176°F)
or more
(d) Load driving

Waveform between terminals SP1 and E1 when vehicle
speed is approx. 20 km/h (12mph).
HINT: As the vehicle speed increases, the number of sig±
nals from SP1 increases.
HINT: In test mode, diagnostic trouble code 42 is output when vehicle speed is 5 km/h (3 mph) or
below.
± ENGINE2JZ±GE ENGINE TROUBLESHOOTINGEG±445

EG±446± ENGINE2JZ±GE ENGINE TROUBLESHOOTING

INSPECTION PROCEDURE
(See page
EG±404)
(See page BE±48)).
Check voltage bertween terminal SP1 of engine control module connector
and body ground.
Check and replace engine control module.
(1) Shift the shift lever to N position.
(2) Jack up one of the rear wheel.
(3) Connect SST (check harness ªAº).
(See page EG±404)
SST 09990±01000
(4) Disconnect power steering ECU connector
and cruise control ECU connector.
(5) Turn ignition switch ON.
Measure voltage between terminal SP1 of engine
control module connector and body ground when
the wheel is turned slowly.
Voltage is generated intermittently.
Repair or replace harness or connector between
ECM and telltale light RH.
Check operation of odometer and trip meter (telltale light RH
(See page
BE±48)).
Check operation of No.1 vehicle speed sensor (See page BE±46).
Replace No.1 vehicle speed sensor.
Repair or replace harness or connector between
telltale light RH and No.1 vehicle speed sensor.
± ENGINE2JZ±GE ENGINE TROUBLESHOOTINGEG±447

DTC 43 Starter Signal Circuit
CIRCUIT DESCRIPTION
When the engine is being cranked, the intake air flow is slow, so fuel vaporization is poor. A rich mixture is there-
fore necessary in order to achieve good startability. While the engine is being cranked, the battery positive volt-
age is applied to terminal STA of the ECM. The starter signal is mainly used to increase the fuel injection volume
for the starting injection control and after±start injection control.
 DTC No. Diagnostic Trouble Code Detecting Condition Trouble Area
 
 
43
 
  No starter signal to ECM
 
 
Open or short in starter signal circuit


Open or short in ignition switch or starter
 
 
43 
 
No starter signal to ECM
 
 
Oen or short in ignition switch or starter
relay circuit


ECM
EG±448± ENGINE2JZ±GE ENGINE TROUBLESHOOTING

INSPECTION PROCEDURE
HINT: This diagnostic chart is based on the premise that the engine is being cranked under normal conditions.
If the engine does not crank, proceed to the matrix chart of problem symptoms on page EG±408.
Check output condition of diagnostic trouble code 43.
Check and replace engine control module.
Setting the test mode.
(1) Turn ignition switch OFF.
(2) Connect terminals TE2 and E1 of DLC2.
(3) Turn ignition switch ON.
(Don't start the engine)
(4) Connect terminals TE1 and E1 of DLC2.
Check if code ª43º is output by the malfunction
indicator lamp.
Code ª43º is output.
Start the engine.
Check if code ª43º disappears.
Code ª43º is not output.
Proceed to next circuit inspection shown on ma-
trix chart (See page
EG±408).
Check for open in harness and connector between engine control module
and starter relay (See page
IN±30).
Repair or replace harness or connector.
Check and replace engine control module.
± ENGINE2JZ±GE ENGINE TROUBLESHOOTINGEG±449

DTC 52 53 55 Knock Sensor Circuit
Knock sensors are fitted one each to the front and rear of the left side of the cylinder block to detect
engine knocking. This sensor contains a piezoelectric element which generates a voltage when it be-
comes deformed, which occurs when the cylinder block vibrates due to knocking. If engine knocking
occurs, ignition timing is retarded to suppress it.
DTC No.Diagnostic Trouble Code Detecting ConditionTrouble Area
No No.1 knock sensor signal to ECM for 4
crank revolutions with engine speed between
1,600 rpm and 5,200 rpm
Engine control computer (for knock control)
malfunction at engine speed between 650 rpm
and 5,200 rpm
No No.2 knock sensor signal to ECM for 4 crank
revolutions with engine speed between 1,600
rpm and 5,200 rpm

Open or short in No.1 knock sensor circuit

No.1 knock sensor (looseness)

ECM

ECM

Open or short in No.2 knock sensor circuit

No.2 knock sensor (looseness)

ECM
If the ECM detects the above diagnosis conditions, it operates the fail safe function in which the correc-
tive retard angle value is set to the maximum value.
DIAGNOSTIC TROUBLE CODE DETECTION DRIVING PATTERN
Purpose of the driving pattern.
(a) To simulate diagnostic trouble code detecting condition after diagnostic trouble code is recorded.
(b) To check that the malfunction is corrected when the repair is completed by confirming that diag±
nostic trouble code is no longer detected.
(1) Start the engine and warm up.
(2) Idle the engine for 3 min.
(3) With the A/C ON, race the engine quickly to 5,000 rpm 3 times.
(Rapidly depress the accelerator pedal and suddenly release it.)
HINT: If a malfunction exists, the malfunction indicator lamp will light up when sudden racing is
performed.
NOTICE: If the conditions in this test are not strictly followed, detection of the malfunction
will not be possible. EG±450
± ENGINE2JZ±GE ENGINE TROUBLESHOOTING

INSPECTION PROCEDURE
HINT: If diagnostic trouble code 52 is displayed, check No.1 knock sensor (for front side) circuit.
If diagnostic trouble code 55 is displayed, check No.2 knock sensor (for rear side) circuit.
If diagnostic trouble code 53 is displayed, replace engine control module.
(See page
EG±404)
Check continuity between terminals KNK1, KNK2 of engine control module
connector and body ground.
(1) Connect SST (check harness ªAº).
(See page EG±404)
SST 09990±01000
(2) Disconnect the engine control modulecon±
nectors.
Measure resistance between terminals KNK1,
KNK2 of engine control module connector and
body ground.
Resistance: 1 M
or higher
± ENGINE2JZ±GE ENGINE TROUBLESHOOTINGEG±451

INSPECTION USING OSCILLOSCOPE

With the engine racing (4,000 rpm) measure wave±
form between terminals KNK1, KNK2 of engine control
module and body ground.
HINT: The correct waveform is as shown.

Spread the time on the horizontal axis, and confirm that
the period of the wave is 123
sec.
(Normal mode vibration frequency of knock sen±
sor: 8.1 KHz).
HINT: If normal mode vibration frequency is not 8.1 KHz,
the sensor is malfunctioning.
KNK Signal Waveform
5 msec./Division
100
sec./Division
Check knock sensor.
Disconnect knock sensor connector.
Measure resistance between the knock sensor ter-
minal and body.
Resistance: 1 M
or higher
Replace knock sensor. (See page EG±245)
Repair or replace harness of connector.
Replace knock sensor. (See page EG±245)
Check and replace engine control module.
Check for open and short in harness and connector between engine control
module and knock sensor (See page
IN±30).
Does malfunction disappear when a good knock sensor is installed?
EG±452± ENGINE2JZ±GE ENGINE TROUBLESHOOTING

(See page EG±397).
CIRCUIT DESCRIPTION
The EGR system is designed to recirculate the exhaust gas, controlled according to the driving condi-
tions, back into the intake air±fuel mixture. It helps to slow down combustion in the cylinder and thus
lower the combustion temperature which, in turn, reduces the amount of NOx emission. The amount
of EGR is regulated by the EGR vacuum modulator according to the load.
If even one of the following conditions is fulfilled,
the VSV is turned ON by a signal from the ECM.
This results in atmospheric air acting on the EGR
valve, closing the EGR valve and shutting off the
exhaust gas (EGR cut±OFF).

Engine coolant temp. below 50°C (122°F)

During deceleration (Throttle valve closed)

Light engine load (amount of intake air very
small).

Engine speed over 5,200 rpm

Traction control is operating
DTC No.Diagnostic Trouble Code Detecting ConditionTrouble Area
EGR gas temp. is 70°C (158°F) or less for 1 ~
4 min. under conditions (a) and (b):
(2) trip detection logic)*
(a) Engine coolant temp.: 63°C (145°F) or
more
(b) EGR operation possible (Example A/T in
3rd speed (5th for M/T), A/C ON, 96
km/h (60 mph), Flat road)

Open in EGR gas temp. sensor circuit

Short in VSV circuit for EGR

EGR hose disconnected, valve stuck

Clogged EGR gas passage

ECM
DIAGNOSTIC TROUBLE CODE DETECTION DRIVING PATTERN
Purpose of the driving pattern.
(a) To simulate diagnostic trouble code detecting condition after diagnostic trouble code is recorded.
(b) To check that the malfunction is corrected when the repair is completed by confirming that diag±
nostic trouble code is no longer detected.
DTC 71 EGR System Malfunction
± ENGINE2JZ±GE ENGINE TROUBLESHOOTINGEG±453

Malfunction: Open in EGR Gas Temp. Sensor Circuit
(Vehicle Speed)
(1)Disconnect the EFI No.1 fuse (30A) for 10 sec. or more, with IG switch OFF. Initiate
test mode (Connect terminal TE2 and E1 of data link connector 2 with IG switch
OFF).
(2)Start engine and warm up.
(3) Idle the engine for 3 min.
(4) With the A/C ON and transmission in 5th position (A/T in 3rd speed) drive at 88 ~ 96
km/h (55 ~ 60 mph) for 4 min. or less.
HINT: If a malfunction exists, the malfunction indicator lamp will light up during step (4).
NOTICE: If the conditions in this test are not strictly followed, detection of the malfunction
will not be possible. EG±454
± ENGINE2JZ±GE ENGINE TROUBLESHOOTING