1995 TOYOTA SUPRA fuel

MATRIX CHART OF PROBLEM SYMPTOMS
When the malfunction code is not confirmed in the diagnostic trouble code check and the problem still can not
be confirmed in the basic inspection, proceed to this matrix chart and troubleshoot according to the numbered
order given below.
EG±438EG±438EG±453EG±460EG±463EG±465EG±470EG±472EG±475EG±457EG±481AC±62ST±3, 12IG±4IG±5IG±7IG±7EG±9AT2±81BE±123IN±35
See page
Suspect area
Symptom
Engine does not crank
No initial combustion
No complete combustion
Engine cranks normally
Cold engine
Hot engine
Incorrect first idle
High engine idle speed
Low engine idle speed
Rough idling
Hunting
Hesitation/Poor acceleration
Muffler explosion (after fire)
Surging
Soon after starting
After accelerator pedal depressed
After accelerator pedal released
During A/C operation
When shifting N to D
Does notstart
Difficult tostart
Poor Idling
Poor
Driveability
Engine Stall
Volume air flow meter circuitECM power source circuitPark/neutral position switch circuitSwitch condition signal circuitEGR systemStarter signal circuitStarter and Starter relayA/C signal circuit (Compressor circuit)VSV circuit for fuel pressure controlFuel pump control circuitIAC valve circuitInjector circuitBack up power source circuitIgnition coilSpark plugIgnition signal circuit (Spark test)CompressionA/T faultyDistributorEngine control module (ECM)Theft deterrent ECU
EG±408± ENGINE2JZ±GE ENGINE TROUBLESHOOTING

DTC 14 Ignition Signal Circuit
CIRCUIT DESCRIPTION
The ECM determines the ignition timing, turns on Tr1 at a predetermined angle (°CA) before the desired ignition
timing and outputs an ignition signal (IGT) º1º to the igniter.
Since the width of the IGT signal is constant, the dwell angle control circuit in the igniter determines the time
the control circuit starts primary current flow to the ignition coil based on the engine rpm and ignition timing one
revolution ago, that is, the time the Tr
2 turns on.
When it reaches the ignition timing, the ECM turns Tr
1 off and outputs the IGT signal ºOº.
This turns Tr
2 off, interrupting the primary current flow and generating a high voltage in the secondary coil which
causes the spark plug to spark. Also, by the counter electromotive force generated when the primary current
is interrupted, the igniter sends an ignition confirmation signal (IGF) to the ECM.
The ECM stops fuel injection as a fail safe function when the IGF signal is not input to the ECM.
 DTC No. Diagnostic Trouble Code Detecting Condition Trouble Area 
 
14
 
  No IGF signal to ECM for 6 consecutive IGT
 
 
Open or short in IGF OR IGT circuit from igniter
to ECM
 
 
14 
 
No IGF signal to ECM for 6 consecutive IGT
signals 
 
to ECM

Igniter

ECM
± ENGINE2JZ±GE ENGINE TROUBLESHOOTINGEG±413

INSPECTION PROCEDURE
(See page IN±30).
(See page EG±404)
Check for spark.
Disconnect the high±tension cord from the distributor, hold its end about 12.5 mm (1/2º) from
the ground, see if spark occurs while the engine is being cranked.
Spark should be generated.
To prevent excess fuel being injected from the injectors during this check. Don't crank the engine
for more than 1 Ð 2 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).
Disconnect igniter connector and check voltage between terminal IGF
of engine control module connector and body ground.
Repair or replace harness or connector.
Replace igniter.
Check and replace engine control module.
(1) Disconnect igniter connector.
(2) Connect SST (check harness ªAº).
See page EG±404)
SST 09990±01000
(3) Turn ignition switch ON.
Measure voltage between terminal IGF of engine
control module connector and body ground.
Voltage: 4.5 ~ 5.5 V EG±414
± ENGINE2JZ±GE ENGINE TROUBLESHOOTING

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 pre-
cisely 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 stoi-
chiometric 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 sen-
sor 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 electromotive force: V).
The ECM judges by the electromotive force from the oxygen sensor whether the air±fuel ratio is 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 sensors include a heater which heats the Zirconia element. The heater is controlled
by the ECM. When the intake air volume is low t(the temperature of the exhaust has is low) current flows to
the heater to heat the sensor for accurate oxygen concentration detection.)
Flange
Platinum Electrode
Solid Electrolyte
(Zirconia Element)
Platinum Electrode
Heater*
1
Coating (Ceramic)
Ideal Air±Fuel Mixture
Richer Ð Air Fuel ratio Ð Leaner
Trouble AreaDTC No.Diagnostic Trouble Code Detecting Condition
Exhaust Gas
Output Voltage
(1)*1Open or snort in heater circuit of main heated
oxygen sensor for 0.5 sec. or more.
(2) (Main heated*1) oxygen sensor signal voltage is
reduced to between 0.35 V and 0.70 V for 60
sec. under conditions (a) ~ (d):
(2) trip detection logic)*
2
(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*
1) oxygen sensor signal
voltage: Alternating above and below 0.45 V
Atmosphere

Open or short in heater circuit of main heated
oxygen sensor

Main heated oxygen sensor heater

ECM

(Main heated*
1) oxygen sensor circuit

(Main heated*1) oxygen sensor
HINT: Diagnostic trouble code ª21º is for the (main heated*1) oxygen sensor (Fr) circuit.
Diagnostic trouble code ª28º is for the (main heated*
1) oxygen sensor (Rr) circuit.
*1: Main heated oxygen sensor ONLY for California specification vehicles.
*2: See page EG±397.
DTC 21 28 (Main Heated*1) Oxygen Sensor Circuit
± ENGINE2JZ±GE ENGINE TROUBLESHOOTINGEG±419

DTC 22 Engine Coolant Temp. Sensor Circuit
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 higher
the coolant temperature, the lower thermistor resist-
ance 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 tem-
perature sensor from the terminal THW via a resistor R.
That is, the resistor R an the engine coolant temperature
sensor are connected in series. When the resistance
value of the engine coolant temperature sensor
changes in accordance with the changes in the coolant
temperature the potential at the terminal THW also
changes. Based on this signal, the ECM increases the
fuel injection volume to improve driveability during cold
engine operation. If the ECM detects the diagnostic
trouble code 22, it operates the fail safe function in
which the engine coolant temperature is assumed to be
80°C (176°F).
DTC No.Diagnostic Trouble Code Detecting ConditionTrouble Area
Open or short in engine coolant temp. sen-
sor circuit for 0.5 sec. or more

Open or short in engine coolant temp.
sensor circuit

Engine coolant temp. sensor

ECM
Reference
VoltageEngine Coolant
Temp.
Resis±
tance
EG±424± ENGINE2JZ±GE ENGINE TROUBLESHOOTING

CIRCUIT DESCRIPTION
See page EG±419 for the circuit description
DTC No.Diagnostic Trouble Code Detecting ConditionTrouble Area
(1) (Main heated*1) oxygen sensor voltage is
0.45 V or less (lean) for 90 sec. under codi±
tions (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
(2)*1Difference of air±fuel ratio feedback
compensation value between front (No.
1 ~ 3 cylinders) and rear (No. 4 ~ 6
cylinders) is more than 15 percentage for
20 sec. or more under conditions (a)
and (b):
(2 trip detection logic)*
2
(a) Engine speed: 2,000 rpm or more
(b) Engine coolant temp.: Between 60°C
(140°F) and 95°C (203°F)
(1)*1Difference of air±fuel ratio feedback
compensation value between front (No.
1 ~ 3 cylinders) and rear (No. 4 ~ 6
cylinders) is more than 15 percentage for
20 sec. or more under conditions (a)
and (b):
(2 trip detection logic)*
2
(a) Engine speed: 2,000 rpm or more
(b) Engine coolant temp.: Between 60°C
(140°F) and 95°C (203°F)
(3)*1Engine speed varies by more than 15 rpm
over the preceding crank angle period
during a period of 20 sec. or more under
conditions (a) and (b):
(2 trip detection logic)*
2
(a) Engine speed: Idling
(b) Engine coolant temp.: Between 60°C
(140°F) and 95°C (203°F)
(2) Engine speed varies by more than 15 rpm
over the preceding crank angle period
during a period of 20 sec. or more under
conditions (a) and (b):
(2 trip detection logic)*
2
(a) Engine speed: Idling
(b) Engine coolant temp.: Between 60°C
(140°F) and 95°C (203°F)
*1: Only for California specification vehicles
*
2: See page EG±397.

Open or short in (main heated*1) oxygen
sensor circuit

(Main heated*
1) oxygen sensor

Ignition system

ECM

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)

Volume air flow meter (air intake)

ECM

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)

Volume air flow meter (air intake)

ECM

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)

Volume air flow meter (air intake)

ECM

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)

Volume air flow meter (air intake)

ECM
DTC 25 26 Air±Fuel Ratio Lean Rich Malfunction
EG±428± ENGINE2JZ±GE ENGINE TROUBLESHOOTING

EG±47
2
IG±4
EG±33
EG±190
EG±457
EG±438
EG±424
EG±426
Check for open and short in harness and connector between engine control mod-
ule and (main heated*) oxygen sensor, engine control module and data link connec-
tor 1 (see page
IN±30).
Check each item found to be a possible cause of problem.
Repair or replace harness or connector.
Repair or replace.
Repair or replace.
Replace (main heated*) oxygen sensor.
Check and replace engine control module.
Does malfunction disappear when a good (main heated*) oxygen sensor is
installed?
Check compression (See page EG±9).
Check each circuit found to be a possible cause of trouble according to the results of the check in
The numbers in the table below show the order in which the checks should be done.
(Main heated*) oxygen sensor
signal from either side
continues at 0 V(Main heated*) oxygen sensor
signal from both sides
continues at 0 V
Possible CauseSee page
Faulty sensor installation
Injector circuit
Misfire
Valve timing
Air leakage
Fuel system
Characteristics deviation
in volume air flow meter
Characteristics deviation
in engine coolant temp. sensor
Characteristics deviation
in intake air temp. sensor
*: Only for California specification vehicles EG±432
± ENGINE2JZ±GE ENGINE TROUBLESHOOTING

EG±4
72
IG±4
EG±33
EG±19
0
EG±457
EG±438
EG±424
EG±426
(See page EG±9).
Check each item found to be a possible cause of problem.
Repair or replace.
Check each circuit found to be a possible cause of trouble according to the results of the check
The numbers in the table below show the order in which the checks should be done.
(Main heated*)
oxygen sensor signal
from either side
continues at 5.0 V
Possible Cause
Injector circuit
Misfire
Valve timing
Air leakage
Fuel system
Characteristics deviation
in volume air flow meter
Characteristics deviation
in volume air flow meter
Characteristics deviation
engine coolant temp. sensor
(Main heated*)
oxygen sensor signal
from both sides
continues at 5.0 V(Main heated*)
oxygen sensor
signals from both
sides are normal
See page
Characteristics deviation
in intake air temp. sensor
Repair or replace.
Replace (main heated*) oxygen sensor.
Check and replace engine control module.
Does malfunction disappear when a good (main heated*) oxygen sensor is
installed?
Check compression (See page EG±9).
*: Only for California specification vehicles
± ENGINE2JZ±GE ENGINE TROUBLESHOOTINGEG±433