1997 TOYOTA SUPRA coolant temperature

FI6448
Intake Air Temp. Sensor
(Inside the mass air flow meter)
3
4P-L
W-B45
65B
BECM
5V
THAR
E2
E2
DI-176
- DIAGNOSTICSENGINE (2JZ-GTE)
404 Author
: Date
:
1997 SUPRA (RM502U)
WIRING DIAGRAM
INSPECTION PROCEDURE
HINT:

If DTC ºP0110º (Intake Air Temp. Circuit Malfunction), ºP0115º (Engine Coolant Temp. Circuit Malfunc-
tion), ºP0120º (Throttle/Pedal Position Sensor/Switch ºAº Circuit Malfunction), are output simulta-
neously, E2 (sensor ground) may be open.
1 Connect the OBD II scan tool or TOYOTA hand-held tester, and read value of in-
take air temperature.
PREPARATION:
(a) Connect the OBD II scan tool or TOYOTA hand-held tester to the DLC3.
(b) Turn ignition switch ON and push the OBD II scan tool or TOYOTA hand-held tester main switch ON.
CHECK:
Read temperature value on the OBD II scan tool or TOYOTA hand-held tester.
OK:
Same as actual intake air temperature.
HINT:

If there is open circuit, OBD II scan tool or TOYOTA hand-held tester indicates - 40°C (- 40°F).

If there is short circuit, OBD II scan tool or TOYOTA hand-held tester indicates 140°C (284°F) or more.
NG - 40 °C (- 40 °F) ............. Go to step 2.
140 °C (284 °F) or more .. Go to step 4.
OK
Check for intermittent problems.
(See page DI-147)

P19603
Engine Coolant Temp. SensorECM
2
1L-Y
W-B44
65B
BTHW
E2R5V
- DIAGNOSTICSENGINE (2JZ-GTE)
DI-179
407 Author
: Date
:
1997 SUPRA (RM502U)
DTC P0115 Engine Coolant Temp. Circuit Malfunction
CIRCUIT DESCRIPTION
A thermistor built into the engine coolant temperature sensor changes the resistance value according to the
engine coolant temperature.
The structure of the sensor and connection to the ECM is the same as in the intake air temperature circuit
malfunction shown on page DI-175.
If the ECM detects the DTC P0115, it operates the fail safe function in which the engine coolant temperature
is assumed to be 80°C (176°F).
DTC No.DTC Detecting ConditionTrouble Area
P0115Open or short in engine coolant temp. sensor circuit

Open or short in engine coolant temp. sensor circuit

Engine coolant temp. sensor

ECM
HINT:
After confirming DTC P0115 use the OBD II scan tool or TOYOTA hand-held tester to confirm the engine
coolant temperature from ºCURRENT DATAº.
Temperature DisplayedMalfunction
- 40°C (- 40°F)Open circuit
140°C (284°F) or moreShort circuit
WIRING DIAGRAM
DI4SP-01

BE6653FI7057A06715
ON
Engine Coolant
Temp. Sensor
2
144
65ECM
5V
THW
E2
BB
DI-180
- DIAGNOSTICSENGINE (2JZ-GTE)
408 Author
: Date
:
1997 SUPRA (RM502U)
INSPECTION PROCEDURE
HINT:

If DTC ºP0110º (Intake Air Temp. Circuit Malfunction), ºP0115º (Engine Coolant Temp. Circuit Malfunc-
tion), ºP0120º (Throttle/Pedal Position Sensor/Switch ºAº Circuit Malfunction) are output simulta-
neously, E2 (sensor ground) may be open.
1 Connect the OBD II scan tool or TOYOTA hand-held tester, and read value of en-
gine coolant temperature.
PREPARATION:
(a) Connect the OBD II scan tool or TOYOTA hand-held tester to the DLC3.
(b) Turn ignition switch ON and push the OBD II scan tool or TOYOTA hand-held tester main switch ON.
CHECK:
Read temperature value on the OBD II scan tool or TOYOTA hand-held tester.
OK:
Same as actual engine coolant temperature.
HINT:

If there is open circuit, OBD II scan tool or TOYOTA hand-held tester indicates - 40°C (- 40°F).

If there is short circuit, OBD II scan tool or TOYOTA hand-held tester indicates 140°C (284°F) or more.
NG - 40°C ( - 40°F) .............. Go to step 2.
140°C (284°F) or more .... Go to step 4.
OK
Check for intermittent problems
(See page DI-147).
2 Check for open in harness or ECM.
PREPARATION:
(a) Disconnect the engine coolant temp. sensor connector.
(b) Connect sensor wire harness terminals together.
(c) Turn ignition switch ON.
CHECK:
Read temperature value on the OBD II scan tool or TOYOTA
hand-held tester.
OK:
Temperature value: 140°C (284°F) or more
OK Confirm good connection at sensor. If OK,
replace engine coolant temp. sensor.
NG

BE6653FI7055P23923A06716
ON
Engine Coolant
Temp. Sensor
2
144
65ECM
5V
THW
E2
BB
Check Harness A
ECM
B65, 44
THW
E2
A00216
ON
Engine Coolant
Temp. SenosrECM
44
655V
THW
E2
BB
- DIAGNOSTICSENGINE (2JZ-GTE)
DI-181
409 Author
: Date
:
1997 SUPRA (RM502U)
3 Check for open in harness or ECM.
PREPARATION:
(a) Connect Check Harness A (See page DI-164).
(b) Connect between terminals THW and E2 of ECM connec-
tor.
HINT:
Engine coolant temp. sensor connector is disconnected. Be-
fore checking, do a visual and contact pressure check for the
ECM connector (See page IN-28).
(c) Turn ignition switch ON.
CHECK:
Read temperature value on the OBD II scan tool or TOYOTA
hand-held tester.
OK:
Temperature value: 140°C (284°F) or more
OK Open in harness between terminals E2 or THW,
repair or replace harness.
NG
Confirm good connection at ECM.
If OK, replace ECM.
4 Check for short in harness and ECM.
PREPARATION:
(a) Disconnect the engine coolant temp. sensor connector.
(b) Turn ignition switch ON.
CHECK:
Read temperature value on the OBD II scan tool or TOYOTA
hand-held tester.
OK:
Temperature value: - 40°C (- 40°F)
OK Replace engine coolant temp. sensor.
NG

BE6653FI7056P25067A06717
ON
Engine Coolant
Temp. SensorECM
5V
THW
E2
ECM
B Connector
DI-182
- DIAGNOSTICSENGINE (2JZ-GTE)
410 Author
: Date
:
1997 SUPRA (RM502U)
5 Check for short in harness or ECM.
PREPARATION:
(a) Disconnect the B connector of ECM (See page DI-164).
HINT:
Engine coolant temp. sensor connector is disconnected.
(b) Turn ignition switch ON.
CHECK:
Read temperature value on the OBD II scan tool or TOYOTA
hand-held tester.
OK:
Temperature value: - 40°C (- 40°F)
OK Repair or replace harness or connector.
NG
Check and replace ECM (See page IN-28).

A00697
Cover
Atmosphere
Housing
Platinum Electrode
Solid Electrolyte
(Zirconia Element)
HeaterPlatinum Electrode
Coating (Ceramic)
Output Voltage
Exhaust GasIdeal Air-Fuel Mixture
Richer - Air Fuel Ratio - Leaner DI-190
- DIAGNOSTICSENGINE (2JZ-GTE)
418 Author
: Date
:
1997 SUPRA (RM502U)
DTC P0125 Insufficient Coolant Temp. for Closed Loop
Fuel Control
CIRCUIT DESCRIPTION
To obtain a high purification rate for the CO, HC and NOx components of the exhaust gas, a three-way cata-
lytic converter is used, but for the 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 ex-
haust gas is reduced and the oxygen sensor informs the ECM of the RICH condition (large electromotive
force: 1 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 time accordingly. However, if malfunction of the oxygen sensor causes out-
put of abnormal electromotive force, the ECM is unable to perform accurate air-fuel ratio control.
The 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 (the temperature of the exhaust gas is low) current flows to the
heater to heat the sensor for accurate oxygen concentration detection.
DTC No.DTC Detecting ConditionTrouble Area
P0125
After the engine is warmed up, heated oxygen sensor output
does not indicate RICH even once when conditions (a), (b) and
(c) continue for at least 2 min. :
(a) Engine speed: 1,500 rpm or more
(b) Vehicle speed: 40 - 100 km/h (25 - 62 mph)
(c) Closed throttle position SW: OFF

Open or short in heated oxygen sensor circuit

Heated oxygen sensor
HINT:
After confirming DTC P0125 use the OBD II scan tool or TOYOTA hand-held tester to confirm voltage output
of heated oxygen sensor from ºCURRENT DATAº.
If voltage output of heated oxygen sensor is 0 V, heated oxygen sensor circuit may be open or short.
DI4ST-01

FI6897
Pressure
Regulator
From Fuel Tank To
Fuel
Tank
(Return) Intake
Manifold ECMVSV
S03472
Battery
B
EB
W-BEFI No.1
R/B
No.2
1
2A2
B-W
222
2
EFI Relay
R/B
No.2
21 5
3B-R5
EA2
B-Y
EA18
VSV for Fuel
Pressure Control B-R1
2W-L73
B
GR24
AECM
FPU
E01
B+
M-REL
- DIAGNOSTICSENGINE (2JZ-GTE)
DI-309
537 Author
: Date
:
1997 SUPRA (RM502U)
Fuel Pressure Control Circuit
CIRCUIT DESCRIPTION
The ECM turns on a VSV (Vacuum Switching Valve) to draw the
air into the diaphragm chamber of the pressure regulator if it de-
tects that the temperature of the engine coolant is too high dur-
ing engine staring.
The air drawn into the chamber increases the fuel pressure to
prevent fuel vapor lock at high engine temperature in order to
help the engine start when it is warm.
Fuel pressure control ends approx. 120 sec. after the engine is
started.
WIRING DIAGRAM
DI4TV-01

229
AIR CONDITIONING
5. AIR CONDITIONING OPERATION
THE A/C AMPLIFIER RECEIVES VARIOUS SIGNALS, I.E., THE ENGINE RPM FROM THE IGNITER, OUTLET
TEMPERATURE SIGNAL FROM THE A/C THERMISTOR, COOLANT TEMPERATURE FROM THE ENGINE COOLANT
TEMP. SENSOR AND THE LOCK SIGNAL FROM THE A/C COMPRESSOR, ETC.
WHEN THE ENGINE IS STARTED AND THE A/C SW (HEATER CONTROL SW) IS ON, A SIGNAL IS INPUT TO THE A/C
AMPLIFIER. AS A RESULT, THE GROUND CIRCUIT IN A/C AMPLIFIER IS CLOSED AND CURRENT FLOWS FROM HTR
FUSE TO TERMINAL 1 OF THE A/C MAGNETIC CLUTCH RELAY  TERMINAL 2 TERMINAL ACMG OF THE ENGINE
CONTROL MODULE TERMINAL A/C TERMINAL MGC OF THE A/C AMPLIFIER TERMINAL GND 
GROUND, TURNING THE RELAY ON, SO THAT THE A/C MAGNETIC CLUTCH IS ON AND THE A/C AMPLIFIER
OPERATES.
AT THE SAME TIME, THE ENGINE CONTROL MODULE DETECTS THE MAGNETIC CLUTCH IS ON AND THE A/C
AMPLIFIER IS OPERATING AND OPENS DIRECTION TO AVOID LOWERING THE ENGINE RPM DURING A/C
OPERATING.
WHEN ANY OF THE FOLLOWING SIGNALS ARE INPUT TO THE A/C AMPLIFIER, THE A/C AMPLIFIER OPERATES TO
TURN OFF THE AIR CONDITIONING.
*ENGINE RPM SIGNAL IS HIGH.
*COOLANT TEMP. SIGNAL IS HIGH.
*A SIGNAL THAT THE TEMPERATURE AT THE AIR OUTLET IS LOW.
*A SIGNAL THAT THERE IS A LARGE DIFFERENCE BETWEEN ENGINE SPEED AND COMPRESSOR SPEED.
*A SIGNAL THAT THE REFRIGERANT PRESSURE IS ABNORMALLY HIGH OR LOW.