TOYOTA SUPRA 1986 Service Repair Manual

See page EG±503.
CIRCUIT DESCRIPTION
The EGR system is designed to recirculate the exhaust gas, controlled according to the driving condi-
tions back into the intake air±fuel mixture. It helps to slow down combustion in the cylinder and thus
lower the combustion temperature which, in turn, reduces the amount of NO
x emission. The amount
of EGR is regulated by the EGR vacuum modulator according to the engine load.
If even one of the following conditions is fulfilled,
the VSV is turned ON by a signal from the ECM.
This resists in atmospheric air acting on the EGR
valve, closing the EGR valve and shutting off the
exhaust gas (EGR cut±OFF).

Engine coolant temp. below 50°C (122°F)

During deceleration (throttle valve closed)

Light engine load (amount of intake air very
small)

Engine speed over 4,800 rpm

Manifold absolute pressure more than 120 kPa
(1.2 kgf/cm
2, 17.4 psi)
DTC No.Diagnostic Trouble Code Detecting ConditionTrouble Area
No No.1 knock sensor signal to ECM for 4
crank revolutions with engine speed between
2,050 rpm and 5,950 rpm

Open EGR gas temp. sensor circuit

Short in VSV circuit for EGR

EGR hose disconnected, valve stuck

Clogged EGR gas passage

ECM
EGR gas temp. and intake air temp. are
60°C(140°F) or less for A/T, 55°C (131°F) or
less for M/T for 1 ~ 4 min. under conditions (a)
and (b):
(2 trip detection logic)*
(a) Engine coolant temp.: 60°C (140°F) or
more
(b) EGR operation possible (Example A/T in
3rd speed (5th for M/T), A/C ON, 96 km/h
(60 mph), Flat road)
Purpose of the driving pattern.
(a) To simulate diagnostic trouble code detecting condition after diagnostic trouble code is recorded.
(b) To check that the malfunction is corrected when the repair is completed by confirming that diagnos±
tic trouble code is no longer detected.
DIAGNOSTIC TROUBLE CODE DETECTION DRIVING PATTERN
DTC 71 EGR System Malfunction
EG±564± ENGINE2JZ±GTE ENGINE TROUBLESHOOTING

Malfunction: Open in EGR Gas Temp. Sensor Circuit
(1) Disconnect the EFI No.1 fuse (30A) for 10 sec. or more, with IG switch OFF.
Initiate test mode (Connect terminal TE2 and E1 of data link connector 2 with IG
switch OFF).
(2) Start the engine and warm up.
(3) Idle the engine for 3 min.
(4) With the A/C ON and transmission in 5th position (A/T in 3rd speed) drive at 88 96
km/h (55 60 mph) for 4 min or less.
HINT: If a malfunction exists, the malfunction indicator lamp will light up during step (4).
NOTICE: If the conditions in this test are not strictly followed, detection of the malfunction
will not be possible.
± ENGINE2JZ±GTE ENGINE TROUBLESHOOTINGEG±565

INSPECTION PROCEDURE
(See page EG±310)
(See page IN±30).
(1) Connect SST (check harness ªAº).
(See page EG±510)
SST 09990±01000
(2) Warm up engine to normal operating temperature.
Measure voltage between terminal EGR of engine con-
trol module connector and body ground.
Voltage: 9 Ð 14 V
Check voltage between terminal EGR of engine control module connector
and body ground.
Check for open and short in harness and connector between EFI main relay
and VSV for EGR, VSV for EGR and engine control module (See page IN±30).
Check resistance between terminals of VSV for EGR.
Repair or replace harness or connector.
Check and replace engine control module.
Remove VSV for EGR. (See page EG±310)
Measure resistance between terminals of VSV for
EGR.
Resistance: 30 Ð 34  at 20°C (68°F)
Replace VSV for EGR. EG±566
± ENGINE2JZ±GTE ENGINE TROUBLESHOOTING

(See page EG±180).
Remove EGR gas temp. sensor.
Measure resistance between terminals of EGR gas
temp. sensor connector.
Resistance: 64 Ð 97k at 50°C (122°F)
11 Ð 1 6k at 100°C (212°F)
2 Ð
k at 150°C (302°F)
Check EGR system (See page EG±180).
Repair EGR system.
Check resistance of EGR gas temp. sensor.
Replace EGR gas temp. sensor.
Repair or replace harness or connector.
Check and replace engine control module.
Check for open in harness and connector between EGR gas temp. sensor
and engine control module. (See page IN±30).
EGR Gas Temp. Sensor
± ENGINE2JZ±GTE ENGINE TROUBLESHOOTINGEG±567

DTC 78 Fuel Pump Control Circuit
CIRCUIT DESCRIPTION
The fuel pump speed is controlled at 2 steps (high speed, low speed) by the condition of the engine (starting,
light load, heavy load), when the engine starts (STA ON), the engine control module sends a Hi signal (battery
positive voltage) to the fuel pump ECU (FPC terminal).
The fuel pump ECU then outputs Hi voltage (battery positive voltage) to the fuel pump so that the fuel pump
operates at high speed.
After the engine starts, during idling or light loads, the engine control module outputs a Low signal (about 9 V)
to the fuel pump ECU, the fuel pump ECU outputs Low battery voltage (about 9 V) to the fuel pump and causes
the fuel pump to operate at low speed.
If the intake air volume increases (high engine load), the engine control module sends a Hi signal to the fuel
pump ECU and causes the fuel pump to operate at high speed.
 
 DTC No.
 
 Diagnostic Trouble Code Detecting Condition
 
 Trouble Area
 
 
 
 
 
 
 
 
(1) Open or short in fuel pump circuit for
1 sec. Or more with engine speed
1,000 rpm or less
(2 trip detection logic)* 
 
 
 O h t i f l ECU i it 
 
 
78
 
 
 
(2) Open in input circuit of fuel pump ECU
(FPC) with engine speed 1,000 rpm or
less
(2 trip detection logic)* 
 
 

Open or short in fuel pump ECU circuit

Fuel pump ECU

Engine control module power source circuit

Fuel pump

Engine control module 
 
 
 
 
 
 
 
(3) Open or short in diagnostic signal line (DI)
of fuel pump ECU with engine speed
1,000 rpm or less
(2 trip detection logic)*
 
 
 
 

Engine control module
*: See page EG±503. EG±568
± ENGINE2JZ±GTE ENGINE TROUBLESHOOTING

(See page IN±30).
Check for ECM power source circuit (See page
EG±576), and check for open in harness and
connector between terminal +B of data link
connector 1 and main relay.
(1) Turn ignition switch ON.
(2) Using SST, connect terminals +B and FP of data
link connector 1.
SST 09843±18020
Check that there is pressure in the hose from the fuel
filter.
Fuel pressure can be felt.
Check fuel pump operation.
Repair or replace harness or connector.
Check for open and short in harness and connector between terminals
+B
+B, FP
FP of the data link connector 1 and fuel pump ECU (See
page IN±30).
Turn ignition switch ON.
Measure voltage between terminal +B of data link con-
nector 1 and body ground.
Voltage: 9 Ð 14 V
Check voltage of terminal +B of data link connector 1.
Check for ECM power source circuit (See
page EG±576), and check for open in harness
and connector between terminal +B of data
link connector 1 and main relay.
INSPECTION PROCEDURE
± ENGINE2JZ±GTE ENGINE TROUBLESHOOTINGEG±569

(See page IN±30).
(See page IN±30).(See page IN±30).
(See page EG±323)
(See page IN±30).
(1) Remove the LH quarter trim panel.
(See page EG±323)
(2) Disconnect fuel pump ECU connector.
Measure voltage between terminals 5 (FPC) and 8 (E)
of fuel pump ECU connector when igintion switch is
turned to START.
Voltage: 4.5 Ð 5.5 V
Check voltage between terminals 5 (FPC) and 8 (E) of fuel pump ECU con-
nector.
Check for open and short in harness and connector between terminal DI of
engine control module and terminal 6 (DI) of fuel pump ECU
(See page IN±30).
Check for open and short in harness and connector between terminal FP of
data link connector 1, fuel pump and body ground)See page IN±30).
Repair or replace fuel pump.
Repair or replace harness or connector.
Replace fuel pump ECU.
Check for open in harness and connector between terminal FPC of engine
control module and terminal 5 (FPC) of fuel pump ECU, terminal 8 (E) of fuel
pump ECU and body ground (See page IN±30).
Repair or replace harness or connector.
Repair or replace harness or connector.
Check and replace engine control module.
EG±570± ENGINE2JZ±GTE ENGINE TROUBLESHOOTING

DTC 51 Switch Condition Signal Circuit
CIRCUIT DESCRIPTION
Park/Neutral Position Switch
The ECM uses the signals from the park/neutral position switch to determine whether the transmission is in park
or neutral, or in some other position.
Air Conditioning Switch Signal
The ECM uses the output from the air conditioning switch to determine whether or not the air conditioning is
operating so that it can increase the idling speed of the engine if necessary.
Throttle Position Sensor IDL Signal
The IDL contacts are mounted in the throttle position sensor, and detects the idle condition.
 DTC No. Diagnostic Trouble Code Detecting Condition Trouble Area
 
 
 
 
 
 
51
 
 
 
 
 
 
(1) 3 sec. or more after engine starts with
closed throttle position switch OFF
(IDL1)
(2) Park/neutral position switch: OFF
(Shift position in ºRº, ºDº, º2º or º1º
position.)
(3) A/C switch ON 
 
 
 
 
 

Throttle position sensor IDL circuit

Accelerator pedal and cable

Park/neutral position switch

A/C switch circuit

ECM
HINT: In this circuit, diagnosis can only be made in the test mode.
± ENGINE2JZ±GTE ENGINE TROUBLESHOOTINGEG±571

INSPECTION PROCEDURE
PNP...Go to page EG±574.
(See page EG±514).
Setting the test mode.
(1) Turn ignition switch OFF.
(2) Connect terminals TE2 and E1 of DLC2.
(3) Turn ignition switch ON.
(For checking terminal IDL, disconnect the
vacuum hose from the throttle body, then ap-
ply vacuum to the throttle opener (See page
EG±292)).
((For checking terminal A/C, start the engine.)
(4) connect terminals TE1 and E1 of DLC2.
Check if code ª51º is output by the malfunction indi-
cator lamp.
*: Before the STA signal is input (ST is not ON), diag±
nostic trouble code 43 is also output.
Diagnostic trouble code 42 is output with vehicle speed
5 km/h (3 mph) or below.
Check output condition of diagnostic trouble code 51.
IDL1...Go to step [2].
PNP....Go to page Eg±574.
A/C....Go to step [3].
Proceed to next circuit inspection shown on matrix
chart (See page Eg±514).
Check output condition of diagnostic trouble code 51.
Throttle Position
Sensor (IDL1)
Condition
Park/Neutral Posi-
tion Switch (PNP)
Code
Accelerator pedal
released
Accelerator pedal
depressed
A/C SW ON
A/C SW OFFA/C Switch (A/C)
P or N position
R, D, 2 or L position
EG±572± ENGINE2JZ±GTE ENGINE TROUBLESHOOTING

(See page EG±292)
(See page EG±510)
(See page AC±62)
(1) Remove throttle body.
(See page EG 291)
(2) Apply vacuum to throttle opener.
(See page EG±292)
Measure resistance between terminals 3 (IDL1)
and 4 (E2) of throttle position sensor connector.
Check throttle position sensor.
Check voltage between terminal A/C of engine control module connector and
body ground.
Adjust or replace throttle position sensor.
(See page EG±292)
Check and repair harness or connector between en-
gine control module and throttle position sensor.
(1) Connect SST (check harness ªAº).
(See page EG±510)
SST 09990±01000
(2) Start the engine.
Measure voltage between terminal A/C of engine
control module and body ground.
Check A/C compressor circuit.
(See page EG±62)
Check and replace engine control module.
± ENGINE2JZ±GTE ENGINE TROUBLESHOOTINGEG±573