TOYOTA SUPRA 1995 Service Repair Manual

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

ECM Power Source Circuit
CIRCUIT DESCRIPTION
When the ignition switch is turned on, battery
voltage is applied to the terminals IGSW of the
ECM, and the main relay control circuit in the
ECM sends a signal to the terminal M±REL of the
ECM, switching on the main relay. This signal
causes current to flow to the coil, closing the con-
tacts of the main relay and supplying power to the
terminal +B of the ECM.
If the ignition switch is turned off, the ECM contin-
ues to switch on the main relay for a maximum of
2 seconds for the initial setting of the IAC valve.
± ENGINE2JZ±GE ENGINE TROUBLESHOOTINGEG±465

(See page EG±404)
Check voltage between terminal +B and E1 of engine control module con-
nector.
(1) Connect SST (check harness ªAº).
(See page Eg±404)
SST 09990±01000
(2) Turn ignition switch ON.
Measure voltage between terminal +B and E1 of
engine control module connector.
Voltage: 9 Ð 14 V
Check and replace engine control module.
Repair or replace harness or connector.
Check voltage between terminal IGSV Check and replace engine control module
connector and body ground.
Proceed to next circuit inspection shown on
matrix chart (See page
EG±408).
Check for open in harness and connector between terminal E1 of engine control
module and body ground (See page
IN±30).
Turn ignition switch ON.
Measure voltage between terminal IGSW of en-
gine control module connector and body ground.
Voltage: 9 Ð 14 V

INSPECTION PROCEDURE
EG±466± ENGINE2JZ±GE ENGINE TROUBLESHOOTING

Check IGN fuse.
Remove IGN fuse from J/B No.1.
Check continuity of IGN fuse.
Continuity
Check for short in the harness and all the com-
ponents connected to IGN fuse (See Electrical
Wiring Diagram).
Check ignition switch.
(1) Remove finish lower panel and finish lower
panel LH.
(2) Remove heater to register duct No.2.
Check continuity between terminals.
Replace ignition switch.
Check and repair harness and connector between
battery and ignition switch, ignition switch and en-
gine control module.
± ENGINE2JZ±GE ENGINE TROUBLESHOOTINGEG±467

Check voltage between terminal M±REL of engine control module connector
and body ground.
Turn ignition switch ON.
Measure voltage between terminal M±REL of en-
gine control module connector and body ground.
Voltage: 9 Ð 14 V
Check and replace engine control module.
Check EFI No.1 Fuse.
Remove EFI No.1 fuse from R/B No.2.
Check continuity of EFI No.1 fuse.
Continuity
Check for short in the harness and all the compo-
nents connected to EFI No.1 fuse (See Electrical
Wiring Diagram).
EG±468± ENGINE2JZ±GE ENGINE TROUBLESHOOTING

Check EFI main relay.
Remove EFI main relay from R/B No.2.
Check continuity between terminals of EFI main
relay shown below.
Replace EFI main relay.
(1) Apply battery voltage between terminals 1
and 2.
(2) Check continuity between terminals 3 and 5.
Repair or replace harness or connector.
Check and repair harness or connector between
EFI No.1 fuse and battery.
Check for open and short in harness and connector between terminal M±REL
of engine control module and body ground(See page
IN±30).
Terminals 3 and 5
Terminals 3 and 5
Terminals 1 and 2
Open
Continuity
Continuity
(Reference value 72
)
± ENGINE2JZ±GE ENGINE TROUBLESHOOTINGEG±469

Back Up Power Source Circuit
CIRCUIT DESCRIPTION
Battery positive voltage is supplied to terminal BATT of the ECM even when the ignition switch is off for use by
the diagnostic trouble code memory and air±fuel ratio adaptive control value memory, etc.
EG±470± ENGINE2JZ±GE ENGINE TROUBLESHOOTING

INSPECTION PROCEDURE
Check EFI No.1 Fuse.
Remove EFI No.1 fuse from R/B No.2.
Check continuity of EFI No.1 fuse.
Continuity
Check for short in the harness and all the com-
ponents connected to EFI No.1 fuse (See Electri-
cal Wiring Diagram).
Connect SST (check harness ªAº).
(See page EG±404)
SST 09990±01000
Measure voltage between terminal BATT of en-
gine control module connector and body ground.
Voltage: 9 Ð 14 V
Check and replace engine control module.
Check and repair harness or connector between
engine control module and EFI No.1 fuse, EFI No.1
fuse and battery.
Proceed to next circuit inspection shown on matrix
chart (See page
EG±408).
Check voltage between terminal BATT of engine control module connector
and body ground.
Are the diagnostic trouble codes still in the memory when the ignition switch
is turned OFF?
± ENGINE2JZ±GE ENGINE TROUBLESHOOTINGEG±471

Injector Circuit
CIRCUIT DESCRIPTION
The injectors are located in the intake manifold. They inject fuel into the cylinders based on the signals
from the engine control module.
INSPECTION USING OSCILLOSCOPE

With the engine idling measure waveform between terminals #10 ~ 60 and E01 of engine
control module.
HINT: The correct waveform is as shown.
EG±472± ENGINE2JZ±GE ENGINE TROUBLESHOOTING