1995 TOYOTA SUPRA fuel

Check for spark.
(1) Remove ignition coil. (See page IG±26)
(2) Remove spark plug.
(3) Install the spark plug to the ignition coil, and connect
the ignition coil connector.
(4) Ground the spark plug.
Check if spark occurs while engine is being cranked.
To prevent excess fuel being injected from injectors dur-
ing this test, don't crank the engine for more than 1Ð2
seconds at a time.
Check for open and short in harness and connector in IGF signal circuit
between engine control module and igniter (See page IN±30).
Repair or replace harness or connector.
Replace igniter.
Check and replace engine control module.
Disconnect igniter connector and check voltage between terminal IGF of
engine control module connector and body ground.
(1) Disconnect igniter connector.
(2) Connect SST (check harness ªAº).
(See page EG±510)
SST 09990±01000
(3) Turn ignition switch ON.
Measure voltage between terminal IGF of engine con-
trol module connector and body ground.
Voltage: 4.5 Ð 5.5 V
INSPECTION PROCEDURE
EG±520± ENGINE2JZ±GTE ENGINE TROUBLESHOOTING

See page EG±503.
CIRCUIT DESCRIPTION
To obtain a high purification rate for the CO, HC and NOx components of the exhaust gas, a three±way
catalytic converter is used, but for most efficient use of the three±way catalytic converter, the air±fuel
ratio must be precisely controlled so that it is always close to the stoichiometric air±fuel ratio.
The oxygen sensor has the characteristic whereby its output voltage changes suddenly in the vicinity
of the stoichiometric air±fuel ratio. This characteristic is used to detect the oxygen concentration in the
exhaust gas and provide feedback to the computer for control of the air±fuel ratio.
When the air±fuel ratio becomes LEAN, the oxygen concentration in the exhaust increases and the
oxygen sensor informs the ECM of the LEAN condition (small electromotive force: 0 V).
When the air±fuel ratio is RICHER than the stoichiometric air±fuel ratio the oxygen concentration in the
exhaust gas is reduced and the oxygen sensor informs the ECM of the RICH condition (large electro-
motive force: 1 V).
The ECm judges by the electromotive force from the oxygen sensor whether the air±fuel ratio if RICH
or LEAN and controls the injection duration accordingly. However, if malfunction of the oxygen sensor
causes an output of abnormal electromotive force, the ECM is unable to perform accurate air±fuel ratio
control.
The main heated oxygen sensor include a heater which heats the Zirconia element. The heater is con-
trolled by the ECM. When the intake air volume is low (the temperature of the exhaust has is low) current
flows to the heater to heat the sensor for accurate oxygen concentration detection.)
Diagnostic Trouble Code Detecting ConditionDTC No.Trouble Area
(1) Open or short in heater circuit of main heated
oxygen sensor for 0.5 sec. or more.
(2) Main heated oxygen sensor signal voltage is
reduced to be 0.35 V and 0.70V for 60 sec.
under condition (a) ~ (d):
(2 trip detection logic)*1
(a) Engine coolant temp.: Between 80°C
(176°F) and 95°C (203°F)
(b) Engine speed: 1,500 rpm or more
(c) Load driving (Example A/T in
overdrive (5th for M/T), A/C ON, Flat
road, 80 km/h (50 mph))
(d) Main heated oxygen sensor signal
voltage: Alternating above and below
0.45V

Open or short in heater circuit of main heated
oxygen sensor

Main heated oxygen sensor heater

ECM

Main heated oxygen sensor circuit

Main heated oxygen sensor
DTC 21 Main Heated Oxygen Sensor Circuit
± ENGINE2JZ±GTE ENGINE TROUBLESHOOTINGEG±525

CIRCUIT DESCRIPTION
The engine coolant temperature sensor senses the
coolant temperature. A thermistor built in the sensor
changes its resistance value according to the coolant
temperature. The lower the coolant temperature, the
greater the thermistor resistance value, and the high-
er the coolant temperature, the lower the thermistor
resistance value (See Fig. 1).
The engine coolant temperature sensor is connected
to the ECM (See wiring diagram). The 5 V power
source voltage in the ECM is applied to the engine
coolant temperature sensor from the terminal THW
via a resistor R. That is, the resistor R and the engine
coolant temperature sensor are connected in series.
When the resistance value of th engine coolant tem-
perature sensor changes in accordance with changes
in the coolant temperature, the potential at the termi-
nal THW also changes. Based on this signal, the ECM
increases the fuel injection volume to improve drive-
ability during cold engine operation. If the ECM re-
cords the diagnostic trouble code 22, it operates the
fail safe function in which the engine coolant tempera-
ture is assumed to be 80°C (176°F).
Diagnostic Trouble Code Detecting ConditionDTC No.Trouble Area
Open or short in engine coolant temp. sensor
circuit for 0.5 sec. or more
Open or short in engine coolant temp.
sensor circuit

Engine coolant temp. sensor

ECM
DTC 22 Engine Coolant Temp. Sensor Circuit
EG±530± ENGINE2JZ±GTE ENGINE TROUBLESHOOTING

DTC 25 26 Air±Fuel Ratio Lean Rich Malfunction
CIRCUIT DESCRIPTION
See EG±525 for the circuit description.
 DTC No. Diagnostic Trouble Code Detecting Condition Trouble Area
 
 
 
 
 
 
 
 
 
 
 
 
 
 
(1) Main heated oxygen sensor voltage is
0.45 V or less (lean) for 90 sec. under
conditions (a) and (b):
(2 trip detection logic)*
2
(a) Engine coolant temp.: 70°C (158°F)
or more
(b) Engine speed: 1,500 rpm or more
 
 
 
 
 
 
 

Open or short in main heated oxygen
sensor circuit

Main heated oxygen sensor

Ignition system

ECM
 
 
 
 
 
 
 
 
25 
 
 
 
 
 
 
 
(2) Engine speed varies by more than 20 rpm
over the preceding crank angle period
during a period of 25 sec. or more under
conditions (a) and (b):
(2 trip detection logic).*
(a) Engine speed: Below 950 rpm
(b) Engine coolant temp.: 80°C
(176°F) or
more 
 
 
 
 
 
 
 

Open and short in injector circuit

Fuel line pressure (injector leak, blockage)

Mechanical system malfunction
(skipping teeth of timing belt)

Ignition system

Compression pressure (foreign object
caught in valve)

Mass air flow meter (air intake)

ECM
 
 
 
 
 
 
 
 
26
 
 
 
 
 
 
 
 
Engine speed varies by more than 20 rpm over
The preceding crank angle period during a
Period of 25 sec. or more under conditions (a)
And (b):
(2 trip detection logic).*
(a) Engine speed: Below 950 rpm
(b) Engine coolant temp.: 80°C
(176°F) or
more 
 
 
 
 
 
 
 

Open and short in injector circuit

Fuel line pressure (injector leak, blockage)

Mechanical system malfunction
(skipping teeth of timing belt)

Ignition system

Compression pressure (foreign object
caught in valve)

Mass air flow meter (air intake)

ECM
*: See page EG±503. EG±534
± ENGINE2JZ±GTE ENGINE TROUBLESHOOTING

(See page EG±9).
EG±261
IG±21
EG±568
EG±583
EG±530
EG±532
EG±544
EG±33
Check each circuit found to be a possible cause of trouble according to the results of the check in
Check each item found to be a possible cause of problem.
Check for open and short in harness and connector between engine
control module and main heated oxygen sensor, engine control module
and data link connector 1 (See page IN±30).
The numbers int he table below show the order in which the checks should be done.
Repair or replace harness or connector.
Repair or replace.
Replace main heated oxygen sensor.
Repair or replace.
Check and replace engine control module.
Check compression (See page EG±9).
Does malfunction disappear when a good main heated oxygen sensor is
installed?
Faulty sensor installation
Air leakage
Misfire
Fuel system
Injector circuit
Characteristics deviation
in engine coolant temp. sensor
Characteristics deviation
in intake air temp. sensor
Characteristics deviation in mass
air flow meter
Va l v e t i m i n g
Main heater oxygen sensor signal
continues at 0 V
EG±538± ENGINE2JZ±GTE ENGINE TROUBLESHOOTING

EG±583
IG±21
EG±33
EG±261
EG±568
EG±544
EG±530
EG±532
EG±9).
Check each circuit found to be a possible cause of trouble according to the results of the check in
Check each item found to be a possible cause of problem.
The numbers int he table below show the order in which the checks should be done.
Air leakage
Misfire
Fuel system
Injector circuit
Characteristics deviation
in engine coolant temp. sensor
Characteristics deviation
in intake air temp. sensor
Characteristics deviation in mass
air flow meter
Va l v e t i m i n g
Main heater oxygen sensor signal
continues at 5.0 VMain heater oxygen sensor
signal is normal
Check compression (See page EG±9).
Repair or replace.
Repair or replace.
Repair main heated oxygen sensor.
Check and replace engine control module.
Does malfunction disappear when a good main heated oxygen sensor is
installed?
± ENGINE2JZ±GTE ENGINE TROUBLESHOOTINGEG±539

CIRCUIT DESCRIPTION
To control maximum turbocharging pressure the turbocharger system includes a waste gate valve con-
trolled by an actuator. The actuator is controlled by the manifold pressure which is duty controlled by the
VSV based on signals from the ECM.
If the ECM detects the below diagnosis conditions, it operates the fail safe function in which the ECM
stops fuel injection.

Actuator (for waste gate valve)

Short in VSV for waste gate valve circuit

ECM
All conditions below are detected continuously
for 2 sec. or more:
(a) Manifold absolute pressure:
200 kPa (2.0 kgf/cm
2, 29 psi) or more
(b) Throttle valve opening angle:
20° or more
(c) Engine speed: 2,400 rpm or more
DTC 34 Turbo Pressure Malfunction
EG±546± ENGINE2JZ±GTE ENGINE TROUBLESHOOTING

DTC 35 Turbo Pressure Sensor Circuit Barometric Pressure (BARO)
Sensor Circuit
CIRCUIT DESCRIPTION
HINT DTC 35 is used to indicate malfunctions in the turbo pressure sensor circuit or BARO sensor circuit.
1. TURBO PRESSURE SENSOR
This sensor detects the air intake chamber pressure and converts the pressure reading into a voltage which
is used to control the turbo pressure by the ECM.
If the ECM detects the below diagnosis conditions, it operates the fail safe function in which the ECM stops
fuel injection at engine speed 2,400 rpm or more and throttle opening angle 20° or more.
 
 DTC No. 
 Circuit 
 Diagnostic Trouble Code Detecting Condition 
 Trouble Area
 
 
 
 
35
 
 
 
 
Turbo
Pressure
Sensor 
 
 
 
Open or short in turbo pressure sensor
circuit for 0.5 sec. or more
 
 
 
 

Open or short in turbo
pressure sensor circuit

Turbo pressure sensor

ECM
2. BARO SENSOR
This sensor is built into the ECM. It is used to detect the atmospheric (absolute) pressure and outputs corre-
sponding electrical signals. Fluctuations in the air pressure cause changes in the intake air density which
can cause deviations in the air±fuel ratio. The signals from BARO sensor are used to make corrections for
the fluctuations. If the ECM detects the below diagnosis conditions, it operates the fail safe function in which
the atmospheric pressure is assumed to be 101.3 kPa (1.03 kgf/cm
2, 14.7 psi).
 DTC No. Circuit Diagnostic Trouble Code Detecting Condition Trouble Area 
 
 
 
 
 
35
 
 
 
 
 
 
BARO
Sensor
 
 
 
 
 
 
Open or short in BARO sensor circuit for
0.5 sec. or more
 
 
 
 
 
 

ECM
± ENGINE2JZ±GTE ENGINE TROUBLESHOOTINGEG±549