1986 TOYOTA SUPRA engine coolant

 Symbols (Terminals No.) STD Voltage (V) Condition
 ACIS (B39)±E01 (B80) 9 ~ 14 IG switch ON
 EVAP (B74)±E01 (B80) 9 ~ 14 IG switch ON 
 EGR (B75) E01 (B80)
 
 Below 2.0
 
 Idling
 EGR (B75)±E01 (B80) 9 ~ 14 Engine speed at 3,500 rpm
 
 
ISC1 (B35), ISC2 (B34)
±E01 (B80)
ISC3 (B33), ISC4 (B32) 
 Pulse generation
(See page EG±475) 
 Idling, when A/C switch ON or OFF
 
 
  VF1 (B29), VF2 (B28)±E1 (B69)
 
 
 1.8 ~ 3.2
 
 
 
Maintain engine speed at 2,500 rpm for 2
minutes after warming up then return to
Idling
 
  OX1 (B48), OX2 (B47)±E1 (B69)
OX3 (A30)* 
 Pulse generation
(See page EG±423) 
 Maintain engine speed at 2,500 rpm for 2
minutes after warming up
 
  HT1 (B73)*, HT2 (B72)*±E01 (B80)
 
 Below 3.0
 
 Idling
 
HT1 (B73) , HT2 (B72) E01 (B80)
HT3 (A36)* 9 ~ 14 IG switch ON
 
 KNK1 (B50), KNK2 (B49)±E1 (B69) 
 
Pulse generation
(See page EG±452) 
 Idling
 
 
NSW (B76) E1 (B69)
 
 9 ~ 14
 
 
IG switch ON
Other shift position in ºPº, ºNº position
 
 
NSW (B76)±E1 (B69) 
 0 ~ 3.0
 
 IG switch ON
Shift position in ºPº, ºNº position
 
 SP1 (A2)±E1 (B69)
 
 Pulse generation
(See page EG±445) 
 IG switch ON
Rotate driving wheel slowly
 
 TE1 (A20)±E1 (B69)
 
 9 ~ 14
 
 IG switch ON
 TE2 (A19)±E1 (B69) 9 ~ 14 IG switch ON
 
W (A6) E1 (B69)
 9 ~ 14 Idling
 W (A6)±E1 (B69) 0 ~ 3.0 IG switch ON 
 OD1 (A12)±E1 (B69) 
 9 ~ 14 
 IG switch ON
 A/C (A34) E1 (B69) 7.5 ~ 14 A/C switch OFF
 A/C (A34)±E1 (B69) 0 ~ 1.5 A/C switch ON (At idling)
 
ACMG (A23) E1 (B69)
 0 ~ 3.0 A/C switch ON (At idling) 
 
ACMG (A23)±E1 (B69) 
 9 ~ 14 
 A/C switch OFF
 FPU (B36)*E01 (B80) 9 ~ 14 IG switch ON
 FPU (B36)*±E01 (B80) Below 2.0 Restarting at high engine coolant temp.
 
ELS (A15) E1 (B69)
 7.5 ~ 14 Defogger switch and taillight switch ON 
 
ELS (A15)±E1 (B69) 
 0 ~ 1.5 
 Defogger switch and taillight switch OFF
*: Only for California specification vehicles EG±406
± ENGINE2JZ±GE ENGINE TROUBLESHOOTING

REFERENCE VALUE OF ECM DATA
HINT: ECM data can be monitored by TOYOTA hand±held
tester.
1. Hook up the TOYOTA hand±held tester to DLC2.
2. Monitor ECM data by following the prompts on the tester
screen.
Please refer to the TOYOTA hand±held tester operator's manual
for further details.
REFERENCE VALUE
 Item Inspection condition Reference value
 
 INJECTOR 
 
Engine cold to hot
Engine idling at normal operating temp.*1
 
 
Gradually decreases
Approx. 2.0 msec.
 IGNITION Increase engine speed Gradually increases
 
 
 
IAC STEP #
 
 
 
Engine idling at normal operating temp.*1
A/C switch ON
A/T shifting in ºDº position
Ignition switch ON (Engine off)
 
 
 
20 ~ 25 steps
Step increases
Step increases
Approx. 125 steps
 ENGINE SPEED RPM kept stable (Comparison with tachometer) No great changes 
 VA F
 
 Engine idling at normal operating temp.*1
Increase engine speed
 
 Approx. 35 ms
Gradually decreases
 ECT Engine at normal operating temp. 75±95°C (185±203°F)*2
 
 
 
THROTTLE
 
 
 
Closed throttle position
Wide open throttle
From closed throttle position to wide open throttle 
 
 
Below 5°
Above 70°
Gradually increases
 
 VEHICLE SPD 
 
During driving
(Comparison with speedometer) 
  No large differences
 TARGET A/FL*5 Engine idling at normal operating temp. 2.50 + 1.25 V*3
 TARGET A/FR*6 Engine idling at normal operating temp. 2.50 + 1.25 V*3
 A/F FB LEFT*5 RPM stable at 2500 rpm with normal operating temp. ON
 A/F FB RIGHT*6 RPM stable at 2500 rpm with normal operating temp. ON
 KNOCK FB Depress throttle pedal suddenly during idling ON
 STA SIGNAL During cranking ON
 CTP SIGNAL Closed throttle position ON
 A/C SIGNAL A/C switch ON ON
 PNP SIGNAL*4 When shifting from ºPº or ºNº position into a position
other than ºPº or ºNº GEAR
 O X L*5 RPM stable at 2500 rpm with normal operating temp. RICH LEAN is repeated O X R*6 RPM stable at 2500 rpm with normal operating temp. RICH LEAN is repeated
*1: If the engine coolant temp. sensor circuit is open or shorted, the ECM assumes an engine coolant temp.
value of 80
°C (176°F).
*
2: When feedback control is forbidden, 0 V is displayed.
*
3: A/T only
*
4: Oxygen sensor (Front)
*
5: Oxygen sensor (Rear)
± ENGINE2JZ±GE ENGINE TROUBLESHOOTINGEG±407

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

(See page EG±404)
(1) Connect SST (check harness ªAº).
(See page EG±404)
(2) Turn ignition switch ON.
Measure voltage between terminals THW and E2
of engine control module connector.
Check for intermittent problems.
(See page EG±399)
Check engine coolant temp. sensor.
Replace engine coolant temp. sensor.
Repair or replace harness or connector.
Check and replace engine control module.
Check for open and short in harness and connector between engine control
module and engine coolant temp. sensor (see page IN±30).
Disconnect the engine coolant temp. sensor connector.
Measure voltage between terminals.
Resistance is within Acceptable Zone on chart.
Check voltage between terminals THW and E2 of engine control module con±
nector.
VoltageEngine Coolant Temp.
(Engine is cool)
(Engine is hot)
INSPECTION PROCEDURE
HINT: If diagnostic trouble codes º22º (engine coolant temperature sensor circuit), º24º (intake air temperature
sensor circuit) and º41º (throttle position sensor circuit) are output simultaneously, E2 (sensor ground)
may be open.
± ENGINE2JZ±GE ENGINE TROUBLESHOOTINGEG±425

DTC 24 Intake Air Temp. Sensor Circuit
CIRCUIT DESCRIPTION
The intake air temp. sensor is built into the volume air flow meter and senses the intake air temperature.
The structure of the sensor and connection to the ECM is the same as in the engine coolant temp. sensor shown
on page EG±424.
If the ECM detects the diagnostic trouble code º24º, it operates the fail safe function in which the
intake air temper-
ature
is assumed to be 20°C (68°F).
 
 DTC No.
 
 Diagnostic Trouble Code Detecting Condition
 
 Trouble Area
 
24
 Open or short in intake air temp. sensor circuit for 
Open or short in intake air temp. sensor circuit

Intake air tempsensor 
 
24 
 
Oen or short in intake air tem . sensor circuit for
0.5 sec. or more 
 

Intake air temp. sensor

ECM
EG±426± ENGINE2JZ±GE ENGINE TROUBLESHOOTING

(See page EG±404)
(1) Connect SST (check harness ªAº).
(See page
EG±404)
SST 09990±01000
(2) Turn ignition switch ON.
Measure voltage between terminals THW and E2 of en-
gine control module connector.
Check for intermittent problems.
(See page EG±399)
Check intake air temp. sensor.
Disconnect the volume air flow meter connector.
Measure voltage between terminals 1 and 2 of volume
air flow meter connector.
Resistance is within Acceptable Zone on chart.
Check voltage between terminals THA and E2 of engine control module con±
nector.
Replace intake air temp. sensor (Replace vol-
ume air flow meter).
Check for open and short in harness and connector between engine control
module and intake air temp. sensor (See page IN±30).
Repair or replace harness or connector.
Check and replace engine control module.
VoltageIntake air temp.
ResistanceIntake air temp.
INSPECTION PROCEDURE
HINT: If diagnostic trouble codes º22º (engine coolant temperature sensor circuit), º24º (intake air temperature
sensor circuit) and º41º (throttle position sensor circuit) are output simultaneously, E2 (sensor ground)
may be open.
± ENGINE2JZ±GE ENGINE TROUBLESHOOTINGEG±427

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