Page 641 of 1807
A00174
ON
EGR Gas Temp. Sensor
2
146
65
B
BTHG
ECM
5V
E2
A00691
ON
EGR Gas Temp. SensorECM
5V
THG
E2
ECM
B Connector
DI-228
- DIAGNOSTICSENGINE (2JZ-GTE)
456 Author: Date:
1997 SUPRA (RM502U)
2 Check for short in harness and ECM.
PREPARATION:
Disconnect the EGR gas temp. sensor connector.
CHECK:
Read EGR gas temp. on the TOYOTA hand-held tester.
OK:
EGR gas temp.: 3.1°C (37.6°F)
OK Replace EGR gas temp. sensor.
NG
3 Check for short in harness or ECM.
PREPARATION:
(a) Disconnect the B connector from ECM
(See page DI-164).
HINT:
EGR gas temp. sensor is disconnected.
(b) Turn ignition switch ON.
CHECK:
Read EGR gas temp. on the TOYOTA hand-held tester.
OK:
EGR gas temp.: 3.1°C (37.6°F)
OK Repair or replace harness or connector.
NG
Check and replace ECM (See page IN-28).
Page 642 of 1807
S03243S03486
A03069
EGR Gas Temp. Sensor
Connector
- DIAGNOSTICSENGINE (2JZ-GTE)
DI-229
457 Author: Date:
1997 SUPRA (RM502U)
4 Check the VSV for EGR (See page DI-217, step 6).
OK Check EGR valve (See page EC-7).
NG
5 Check operation of the VSV for EGR (See page SF-77).
NG Replace VSV for EGR.
OK
Check for short in harness and connector
between VSV and ECM (See page IN-28).
OBDII scan tool (excluding TOYOTA hand-held tester)
1 Check resistance of EGR gas temp. sensor.
PREPARATION:
Disconnect the EGR gas temp. sensor connector.
CHECK:
Measure resistance between terminals of EGR gas temp. sen-
sor connector.
OK:
Resistance: 2.5 kW or more.
(Not immediately after driving)
HINT:
If there is short circuit, ohmmeter indicates 200 W or less.
NG Replace EGR gas temp. sensor.
OK
Page 643 of 1807
DI-230
- DIAGNOSTICSENGINE (2JZ-GTE)
458 Author: Date:
1997 SUPRA (RM502U)
2 Check for short in harness and connector between EGR gas temp. sensor and
ECM (See page EC-7).
NG Repair or replace harness or connector.
OK
3 Check the VSV for EGR (See page DI-217, step 6).
OK Check EGR valve (See page EC-7).
NG
4 Check operation of the VSV for EGR (See page IN-18).
NG Replace VSV for EGR.
OK
5 Check for short in harness and connector between VSV and ECM
(See page EC-7).
NG Repair or replace harness or connector.
OK
Check and replace ECM (See page EC-7).
Page 644 of 1807

FI7081
Waveform of oxygen sensor
before catalystNormal
catalystWaveform of oxygen sensor
after catalyst
- DIAGNOSTICSENGINE (2JZ-GTE)
DI-231
459 Author: Date:
1997 SUPRA (RM502U)
DTC P0420 Catalyst System Efficiency Below Threshold
CIRCUIT DESCRIPTION
The ECM compares the waveform of the oxygen sensor located before the catalyst with the waveform of
the oxygen sensor located after the catalyst to determine whether or not catalyst performance has deterio-
rated.
Air-fuel ratio feedback compensation keeps the waveform of the oxygen sensor before the catalyst repeat-
edly changing back and forth from rich to lean.
If the catalyst is functioning normally, the waveform of the oxygen sensor after the catalyst switches back
and forth between rich and lean much more slowly than the waveform of the oxygen sensor before the cata-
lyst.
But when both wavaforms change at a similar rate, it indicates that catalyst performance has deteriorated.
DTC No.DTC Detecting ConditionTrouble Area
P0420
After the engine and the catalyst are warmed up, and while the
vehicle is driven within the set vehicle and engine speed range,
the waveforms of the heated oxygen sensors (bank 1 sensor 1
and bank 1 sensor 2) have the same amplitude
(2 trip detection logic)
Three-way catalytic converter
Open or short in heated oxygen sensor circuit
Heated oxygen sensor
DI4T5-01
Page 645 of 1807

FI7132
Engine Speed
2,500 - 3,000 rpm
Idling
IG SW OFF
Warmed up 3 min. or so CheckTime (1)(2)(3) (4)
FI6514
OX Signal Waveform (Oscilloscope)
200 msec./Division 1.0 V
0 V DI-232
- DIAGNOSTICSENGINE (2JZ-GTE)
460 Author: Date:
1997 SUPRA (RM502U)
CONFIRMATION ENGINE RACING PATTERN
(1) Connect the TOYOTA hand-held tester to the DLC3, or connect the probe of the oscilloscope between
terminals OX1, OX2, and E1 of ECM.
(2) Start engine and warm it up with all accessories switched OFF until water temperature is stable.
(3) Race the engine at 2,500 ~ 3,000 rpm for about 3 min.
(4) After confirming that the waveforms of the heated oxygen sensors, bank 1 sensor 1 (OX1), oscillate
around 0.5 V during feedback to the ECM, check the waveform of the heated oxygen senor, bank 1 sensor
2 (OX2).
HINT:
If there is a malfunction in the system, the waveform of the
heated oxygen senor, bank1 sensor 2 (OX2), is almost the
same as that of the heated oxygen sensors, bank 1 senor 1
(OX1), on the left.
There are some cases where, even though a malfunction ex-
ists, the MIL may either light up or not light up.
Page 646 of 1807
- DIAGNOSTICSENGINE (2JZ-GTE)
DI-233
461 Author: Date:
1997 SUPRA (RM502U)
INSPECTION PROCEDURE
1 Are there any other code (besides DTC P0420) being output?
YES Go to relevant DTC chart.
NO
2 Check heated oxygen senor (bank 1, sensor 1) (See page DI-193).
NG Repair or replace.
OK
3 Check heated oxygen senor (bank1, sensor 2) (See page DI-199).
NG Repair or replace.
OK
Replace three-way catalytic converter.
Page 647 of 1807

S05422
To Turbo
Charcoal
Canister
Fuel Tank
ECMIntake Manifold VSV for
EVAP
S01079
Battery
EB
W-B
BB-W
R/B No.2
EFI No.1
EFI Main Relay
2 2A
2
2 2
2
35
1 2
B-R
B-YB-REA22VSV for EVAP
1274
B
ECM
EVAP
E01
B+
GR24
A
M-REL
V
EA18 1 DI-234
- DIAGNOSTICSENGINE (2JZ-GTE)
462 Author: Date:
1997 SUPRA (RM502U)
DTC P0441 Evaporative Emission Control System
Incorrect Purge Flow
CIRCUIT DESCRIPTION
To reduce HC emissions, evaporated fuel from the fuel tank is routed through the charcoal canister to the
intake manifold for combustion in the cylinders.
The ECM changes the duty signal to the VSV for EVAP so that the intake quantity of HC emissions is ap-
propriate for the driving conditions (engine load, engine speed, etc.) after the engine is warme up.
DTC No.DTC Detecting ConditionTrouble Area
P0441
The proper response to the computer command does not oc-
cur
(2 trip detection logic)
Open or short in VSV circuit for EVAP
VSV for EVAP
Vacuum hose blocked or disconnected
ECM
Charcoal canister
WIRING DIAGRAM
DI4T6-01
Page 648 of 1807
A00711
ON
Air
Air
FEF
E
VSV: ON VSV: OFF
- DIAGNOSTICSENGINE (2JZ-GTE)
DI-235
463 Author: Date:
1997 SUPRA (RM502U)
INSPECTION PROCEDURE
TOYOTA hand-held tester
1 Connect the TOYOTA hand-held tester and check operation of VSV for EVAP.
PREPARATION:
(a) Connect the TOYOTA hand-held tester to the DLC3.
(b) Turn ignition switch ON and push the TOYOTA hand-held
tester main switch ON.
(c) Select the ACTIVE TEST mode on the TOYOTA hand-
held tester.
CHECK:
Check operation of VSV when VSV is operated by the TOYOTA
hand-held tester.
OK:
VSV is ON:
Air from pipe E flows out through pipe F.
VSV is OFF:
Air does not flow from pipe E to pipe F.
OK Go to step 4.
NG
2 Check VSV for EVAP (See page SF-71).
NG Replace VSV for EVAP.
OK
3 Check for open and short in harness and connector between EFI main relay
(Marking: EFI MAIN) and ECM (See page IN-28).
NG Repair or replace harness or connector.
OK
Check and replace ECM (See page IN-28).