TOYOTA SUPRA 1986 Service Repair Manual

INSPECTION PROCEDURE
(See page
EG±404)
(See page
EG±240)
Check voltage between terminal EGR of engine control module connector
and body ground.
(1) Connect SST (check harness ªAº).
(See page EG±404)
SST 09990±0100
(2) Warm up engine to normal operating
temperature.
Measure voltage between terminal EGR of engine
control module connector and body ground.
Voltage: 9 Ð 14 V
Repair or replace harness of connector.
Check resistance between terminals of VSV for EGR.
Remove VSV for EGR. (See page EG±240)
Measure resistance between terminals of VSV for
EGR.
Resistance: 38.5 Ð 44.5
at 20°C (68°F)
Check and replace engine control module.
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)
Replace VSV for EGR.
± ENGINE2JZ±GE ENGINE TROUBLESHOOTINGEG±455

Check EGR system (See page Eg±168).
Remove EGR gas temp. sensor.
Measure resistance between terminals of EGR gas
temp. sensor connector.
Resistance: 64 Ð 97 k
at 50°C (122°F)
11 Ð 16 k
at 100°C (1212°F)
2 Ð 4 k
at 150°C (302°F)
Replace EGR gas temp. sensor.
Repair EGR system.
Replace EGR gas temp. sensor.
Repair or replace harness or connector.
Check and replace engine control module.
Check resistance of EGR gas temp. sensor.
Check for open in harness and connector between EGR gas temp. sensor
and engine control module. (See page
IN±30)
EG±456± ENGINE2JZ±GE ENGINE TROUBLESHOOTING

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 Lo 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 i f l ECU i i 
 
 
 
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±397.
± ENGINE2JZ±GE ENGINE TROUBLESHOOTINGEG±457

(1) Turn ignition switch ON.
(2) Using SST, connect terminals +B and FP of
data link connector1.
SST 09843±18020
Check that there is pressure in the hose from the
fuel filter.
Fuel pressure can be felt.
Repair or replace harness or connector.Repair or replace harness or connector.
Check fuel pump operation.
Check for open and short in harness and connector between terminals +B
e +B, FP e FP of the data link connector 1 and fuel pump ECU (See page
IN±30).
Check voltage of terminal +B of data link connector 1.
Turn ignition switch ON.
Measure voltage between terminal +B of data link
connector 1 and body ground.
Fuel pressure can be felt.
Check for ECM power source circuit (See page
EG±465), and check for open in harness and con-
nector between terminal +B of data link connec-
tor 1 and main relay.
INSPECTION PROCEDURE
EG±458± ENGINE2JZ±GE ENGINE TROUBLESHOOTING

(See page IN±30).
(See page EG±252)
(See page IN±30).
(1) Remove the LH quarter trim panel.
(See page EG±252)
(2) Disconnect fuel pump ECU connector.
Measure voltage between terminals 3 (FPC) an 1
(E) of fuel pump ECU connector when ignition
switch is turned to START.
Voltage: 4.5 Ð 5.5 V
Repair or replace harness or connector.
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).
Check for open in harness and connector between terminal FPC of engine
control module and terminal 3 (FPC) of fuel pump ECU, terminal 1 (E) of fuel
pump ECU and body ground (See page IN±30).
Repair or replace harness or connector.
Repair or replace fuel pump.
Check voltage between terminals 3 (FPC) and 1 (E) of fuel pump ECU con-
nector.
Replace fuel pump ECU.
Repair or replace harness or connector.
Check for open and short in harness and connector between terminal DI of
engine control module and terminal 2 (DI) of fuel pump ECU
(See page IN±30).
Check and replace engine control module.
± ENGINE2JZ±GE ENGINE TROUBLESHOOTINGEG±459

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
 
 
 
 
(1) 3 sec. or more after engine starts with
closed throttle position switch OFF
(IDL1)
 
 
Throttle position sensor IDL circuit
Alt dldbl 
 51
 
 
(IDL1)
(2) Park/neutral position switch: OFF
(Shiftposition inºRººDºº2ºorºLº
 
 

Accelerator pedal and cable

Park/neutral position switch

A/C switch circuit 
 
 
 
(Shift position in ºRº, ºDº, º2º or ºLº
position.)
(3) A/C switch ON 
 

A/C switch circuit

ECM
HINT: In this circuit, diagnoses can only be made in the test mode.
EG±460± ENGINE2JZ±GE ENGINE TROUBLESHOOTING

INSPECTION PROCEDURE
(EG±463).
Check output condition of diagnostic trouble code 51.
*: Before the STA signal is input (ST is not ON),
diagnostic trouble code 43 is also output.
Diagnostic trouble code 42 is output with vehicle
speed 5 km/h (3 mph) or below.
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 apply
vacuum to the throttle opener (See page
EG±219)).
(For checking terminal A/C, start the engine.)
(4) Connect terminals TE1 and E1 of DLC1 or
DLC2.
Check if code ª51º is output by the malfunction indi-
cator lamp.
Proceed to next circuit inspection shown on matrix
chart (See page EG±408).
IDL1...Go to step [2].
PNP....Go to page EG±463.
A/C....Go to step [3].
Condition
Throttle Position
Park/Nuetral Posi±
Code
tion Switch (PNP)
P or N position
released
R,D, 2 or L position
Accelerator pedal
Accelerator pedal
depressed
A/C SW ON
A/C SW OFFA/C Switch (A/C)
Sensor (IDL1)
± ENGINE2JZ±GE ENGINE TROUBLESHOOTINGEG±461

(See page EG±404)
Check throttle position sensor.
(1) Disconnect throttle position sensor connector.
(2) Disconnect the vacuum hose from the throttle
body. than apply vacuum to the throttle opener
(See page EG±219).
Measure resistance between terminals 2 (IDL1)
and 1 (E2) of throttle position sensor connector.
Adjust or replace throttle position sensor.
(See page
EG±223)
Check and repair harmless or connector between en-
gine control module and throttle position sensor.
Check voltage between terminal A/C of engine control module connector and
body ground.
(1) Connect SST (check harness ªAº).
(See page EG±404)
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 AC±62)
Check and replace engine control module.
Throttle Valve
Fully closed
Opened
Less than 0.5 k

1 M
or higher
Resistance
EG±462± ENGINE2JZ±GE ENGINE TROUBLESHOOTING

Park Neutral Position Switch Circuit
CIRCUIT DESCRIPTION
The park/neutral position switch goes on when the shift lever is in the N or P shift position. When it goes on the
terminal NSW of the ECM is grounded to body ground via the starter relay and theft deterrent ECU, thus the
terminal NSW voltage becomes 0 V. When the shift lever is in the D, 2, L or R position, the park/neutral position
switch goes off, so the voltage of ECM terminal NSW becomes positive battery voltage, the voltage of the ECM
internal power source.
If the shift lever is moved from the N position to the D position, this signal is used for air±fuel ratio correction
and for idle speed control (estimated control), etc.
When the park/neutral position switch is off, code º51º is output in the test mode diagnosis. (This is not abnor-
mal.)
± ENGINE2JZ±GE ENGINE TROUBLESHOOTINGEG±463

INSPECTION PROCEDURE
HINT: This diagnostic chart is based on the premise that the engine is being cranked under normal conditions.
If the engine does not crank, proceed to the matrix chart of problem symptoms on page EG±408.
(See page EG±408).
(See page IN±30).
Check output condition of diagnostic trouble code 51
(1) Connect terminals TE2 and E1 of DLC2.
(2) Turn ignition switch ON.
(3) Crank the engine.
(4) Connect terminals TE1 and E1 of DLC2.
Check if diagnostic trouble code ª51º is output
when the shift lever is in the P and D shift positions.
Check and replace engine control module.
Proceed to next circuit inspection shown on matrix
chart (See page Eg±408).
Check for open in harness and connector between engine control module
and park/neutral position switch (See page
IN±30).
Repair or replace harness or connector.
Replace park/neutral position switch.
Check and replace engine control module.
Check park/neutral position switch (See page AT1±81).
Shift
Position Result
Normal Code
Normal Code
Normal Code
NG Type ING Type II
Code 51
Code 51
Code 51
OK
ªºPº
ªºDº
EG±464± ENGINE2JZ±GE ENGINE TROUBLESHOOTING