TOYOTA SUPRA 1986 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.)
EG±574± ENGINE2JZ±GTE ENGINE TROUBLESHOOTING

INSPECTION PROCEDURE
HINT: This diagnosis 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±514.
(See page EG±514).
(See page IN±30).
(See page AT2±101).
(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 output condition of diagnostic trouble code 51.
Check for open in harness and connector between engine control module
and park/neutral position switch (See page IN±30).
Check and replace engine control module.
Proceed to next circuit inspection shown on matrix
chart (See page EG±514).
Repair or replace harness or connector.
Replace park/neutral position switch.
Check and replace engine control module.
Check park/neutral position switch (See page AT2±101).
Shift
PositionResult
NG Type ING Type II
Normal CodeNormal Code
Normal CodeCode 51
Code 51
Code 51
''P''
''D''
OK
NG
Type I
NG
Type II
± ENGINE2JZ±GTE ENGINE TROUBLESHOOTINGEG±575

ECM Power Source Circuit
CIRCUIT DESCRIPTION
When the ignition switch is turned on, battery volt-
age is applied to the terminal IGSW of the ECM,
and the main relay control circuit in the ECM sends
a signal to the terminal M±REL of the ECM, switch-
ing on the main relay. This signal causes current to
flow to the coil, closing the contacts 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. EG±576
± ENGINE2JZ±GTE ENGINE TROUBLESHOOTING

(See page EG±510)
(1) Connect SST (check harness ªAº).
(See page EG±510)
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 voltage between terminal +B and E1 of engine control module
connector.
Proceed to next circuit inspection shown on
matrix chart (See page EG±514).
Repair or replace harness or connector.
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
Check voltage between terminal IGSW of engine control module connector
and body ground.
INSPECTION PROCEDURE
± ENGINE2JZ±GTE ENGINE TROUBLESHOOTINGEG±577

Check for short in the harness and all the compo-
nents connected to IGN fuse (See Electrical Wir-
ing Diagram).
Remove IGN fuse from J/B No.1.
Check continuity of IGN fuse.
Continuity
Check IGN fuse.
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.
Check and repair harness and connector between
battery and ignition switch, ignition switch and en-
gine control module.
Replace ignition switch.
Terminal
Switch position
LOCK
ACC
ON
START
continuity
EG±578± ENGINE2JZ±GTE ENGINE TROUBLESHOOTING

Check for short in the harness and all the compo-
nents connected to EFI No.1 fuse (See Electrical
Wiring Diagram).
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 voltage between terminal M±REL of engine control module connector
and body ground
Check EFI No.1 Fuse.
Remove EFI No.1 fuse from R/B No.2.
Check continuity of EFI No.1 fuse.
Continuity
Check and replace engine control module.
± ENGINE2JZ±GTE ENGINE TROUBLESHOOTINGEG±579

(See page IN±30).
Remove EFI main relay from R/B No.2.
Check continuity between terminals of EFI main
relay shown below.
Check EFI main relay.
(1) Apply battery positive voltage between termi±
nals 1 and 2.
(2) Check continuity between terminals 3 and 5.
Replace EFI main relay.
Repair or replace harness or connector.
Check for open and short in harness and connector between terminals
M±REL of engine control module and body ground (See page IN±30).
Check and repair harness or connector between EFI
No.1 fuse and battery.
Continuity
Continuity
Terminals 3 and 6
Terminals 3 and 5
Terminals 1 and 2 (Reference value 72
)
Open
EG±580± ENGINE2JZ±GTE ENGINE TROUBLESHOOTING

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.
± ENGINE2JZ±GTE ENGINE TROUBLESHOOTINGEG±581

INSPECTION PROCEDURE
(See page EG±510)
Check and repair harness or connector between
engine control module and EFI No.1 fuse, EFI No.1
fuse and battery.
Remove EFI No.1 fuse from R/B No.2.
Check continuity of EFI No.1 fuse.
Continuity
Check EFI No.1 Fuse.
Check voltage between terminal BATT of engine control module connector
and body ground.
Connect SST (check harness ªAº).
See page EG±510)
SST 09990±01000
Measure voltage between terminal BATT of en-
gine control module connector and body ground.
Voltage: 9 Ð 14 V
Check for short in the harness and all the compo-
nents connected to EFI No.1 fuse (See attached
wiring diagram).
Are the diagnostic trouble codes still in the memory when the ignition switch
is turned OFF?
Check and replace engine control module.
Proceed to next circuit inspection shown on matrix
chart (See page EG±514).
EG±582± ENGINE2JZ±GTE ENGINE TROUBLESHOOTING

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.

With engine idling measure waveform between terminals # 10 ~ 60 and E01 of engine control
module.
HINT: The correct waveform is as shown.
INSPECTION USING OSCILLOSCOPEReferenceINSPECTION USING OSCILLOSCOPE
± ENGINE2JZ±GTE ENGINE TROUBLESHOOTINGEG±583