TOYOTA SUPRA 1995 Service Repair Manual

DTC 32 34 Control Switch Circuit (Cruise Control Switch)
CIRCUIT DESCRIPTION
This circuit carries the SET/COAST, RESUME/ACCEL and CANCEL signals (each voltage) to the ECU.
 
 Code No. 
 Diagnosis 
 Trouble area
 
 
32 
 
Short in, control switch circuit. 
 
 Cruise control switch.
 Harness or connector between control
 
 
34 
 
Voltage abnormality in control switch 
 
Harness or connector between control
switch and ECU.
 ECU
WIRING DIAGRAM
± BODY ELECTRICAL SYSTEMCRUISE CONTROL SYSTEMBE±179

INSPECTION PROCEDURE
Proceed to next circuit inspection shown on matrix
chart (See page
BE±170).
(1) See input signal check on page BE±169.
(2) Check the indicator light operation when each of
the SET/COAST, RESUME/ACCEL and CAN±
CEL is turned ON.
Input signal check.
SET/COAST, RESUME/ACCEL Switch
The signals shown in the table on the left should
be output when each switch is ON. The signal
should disappear when the switch is turned OFF.
CANCEL Switch.
The indicator light goes off when the cancel
switch is turned ON.
Check voltage between terminal CCS of ECU connector and body ground.
Proceed to next circuit inspection shown on matrix
chart (See page
BE±170).
(1) Turn ignition switch ON.
(2) Measure voltage between terminal CCS of ECU
connector and body ground, when each of the
SET/COAST, RESUME/ACCEL and CANCEL is
turned ON.
Remove ECU with connectors still connected.
Switch position
Neutral
RES/ACC
SET/COAST
CANCEL
Voltage
 


Go to step [3].
BE±180± BODY ELECTRICAL SYSTEMCRUISE CONTROL SYSTEM

control switch (See page IN±30).
Switch position
Neutral
RES/ACC
SET/COAST
CANCEL
Replace cruise control switch.
Measure resistance between terminals 3 and 4 of
control switch connector when control switch is
operated.
Repair or replace harness or connector.
Check and replace ECU.
When diagnostic trouble code 34 is displayed, carefully
check that resistance is always 8 in neutral position,
particularly when switching between RES/ACC and
SET/COAST.
(1) Remove steering wheel center pad.
(2) Disconnect control switch connector (See
page RS Section).
Check control switch.
Check for open and short in harness and connector between ECU and
Resistance
± BODY ELECTRICAL SYSTEMCRUISE CONTROL SYSTEMBE±181

Stop Light Switch Circuit
CIRCUIT DESCRIPTION
When the brake is on, battery voltage normally applies through the stop fuse and stop switch to terminal STP±of
the ECU, and the ECU turns the cruise control off.
A fail±safe function is provided so that cancel functions normally, even if there is a malfunction in the stop light
signal circuit.
(1) If the harness connected to terminal STP±has an open, terminal STP±will have battery positive voltage
and the cruise control will be turned off, also SET not occurring.
(2) If the stop fuse is open, terminal STP + becomes approx.
0 V when the brake is turned on, so the ECU performs cancel function normally.
Also, when the brake is on, the magnetic clutch is cut mechanically by the stop light switch, turning the cruise
control off. (See page BE±173 for operation of the magnetic clutch.)
WIRING DIAGRAM
BE±182± BODY ELECTRICAL SYSTEMCRUISE CONTROL SYSTEM

chart (See page BE±170).
Proceed to next circuit inspection shown on matrix
chart (See page
BE±170).
(1) See input signal check on page BE±169.
(2) Check the indicator light when the brake pedal is
depressed.
Check operation of stop light.
Check voltage between terminal STP+, STP± of ECU connector and body
ground.
(1) Turn ignition switch ON.
(2) Measure voltage between terminal STP+, STP±
of ECU connector and body ground, when the
brake pedal is depressed and released.
Remove ECU with connectors still connected.
Input signal check.
Proceed to next circuit inspection shown on matrix
chart (See page
BE±170).
The indicator light goes off when the brake pedal is de-
pressed.
Check the stop light comes on when the brake pedal is depressed, and turns off when brake pedal is re-
leased.
Check stop light circuit.
Repair or replace harness or connector.
Check and replace ECU.
Check for open in harness and connectors between terminal STP+ of ECU and stop
light switch, terminal STP± of ECU and stop light switch (See page
IN±30).
Depressed
Released
INSPECTION PROCEDURE
± BODY ELECTRICAL SYSTEMCRUISE CONTROL SYSTEMBE±183

Idle Switch Circuit
CIRCUIT DESCRIPTION
When the idle switch is turned ON, a signal is sent to the ECU. The ECU uses this signal to correct the discrepan-
cy between the throttle valve position and the actuator position sensor value to enable accurate cruise control
at the set speed. If the idle switch is malfunctioning, problem symptoms also occur in the engine, so also inspect
the engine.
WIRING DIAGRAM
BE±184± BODY ELECTRICAL SYSTEMCRUISE CONTROL SYSTEM

INSPECTION PROCEDURE
Proceed to next circuit inspection shown on matrix
chart (See page
BE±170).
(1) Turn ignition switch ON.
(2) Measure voltage between terminal IDL of ECU
connector and body ground, when the throttle
valve is fully closed and fully opened.
Check voltage between terminal IDL of ECU connector and body ground.
Check throttle position sensor.
Measure resistance between terminals 1 and 2 of
throttle position sensor connector, when the throttle
valve is fully closed and fully opened.
(1) Remove cruise control ECU with connectors still
connected.
(2) Disconnect ECM and ABS & TRAC ECU
connector.
Disconnect throttle position sensor connector.
Throttle valve position
Fully opened
Fully closed
Voltage
Throttle valve position
Fully opened
Fully closed
Voltage
Repair or replace harness or connector.
Check and replace ECU.
Check for open and short in harness and connector between ECU and throttle
position sensor, throttle position sensor and body ground (See page
IN±30).
± BODY ELECTRICAL SYSTEMCRUISE CONTROL SYSTEMBE±185

Electronically Controlled Transmission Communication Circuit
CIRCUIT DESCRIPTION
When driving uphill under cruise control, in order to reduce shifting due to ON±OFF overdrive operation and
to provide smooth driving, when down shifting in the electronically controlled transmission occurs, a signal to
prevent upshift until the end of the uphill slope is sent from the cruise control ECU to the electronically controlled
transmission.
Terminal ECM of the cruise control ECU detects the shift change signal (output to electronically controlled trans-
mission No.2 solenoid) from the electronically controlled transmission.
If vehicle speed down, also when terminal ECT of the cruise control ECU receives down shifting signal, it sends
a signal from terminal OD to ECM to cut overdrive until the end of the uphill slope, and the gear shifts are reduced
and gear shift points in the electronically controlled transmission are changed.
WIRING DIAGRAM
BE±186± BODY ELECTRICAL SYSTEMCRUISE CONTROL SYSTEM

INSPECTION PROCEDURE
(1) Disconnect ECU connector.
(2) Turn ignition switch ON.
(3) Measure voltage between terminal OD of har±
ness side connector of ECU and body ground.
Check voltage between terminal OD of harness side connector ECU and
body ground.
Check operation of overdrive.
Remove ECU with connector still connected.
Check and Repair Electronically controlled transmis-
sion (See AT section).
Voltage: 10 ± 14 V
Go to step
Go to step
Test drive after engine warm up.
Check that overdrive ON e OFF occurs with operation of OD switch ON±OFF.
± BODY ELECTRICAL SYSTEMCRUISE CONTROL SYSTEMBE±187

(See page IN±30).
Check voltage between terminal ECT of cruise control ECU connector and
body ground (On test drive).
(1) Connect ECU connector.
(2) Test drive after engine warm up.
Proceed to next circuit inspection shown on
matrix chart (See page BE±170).
Check voltage between terminal ECT of
cruise control ECU connector and body
ground when OD switch is on and off.
Repair or replace harness or connector.
Check and replace ECU.
Check and repair ECU.
Repair or replace harness or connector.
Check for open and short in harness and connector between terminal OD1
of ECU and terminal OD1 of ECM (See page IN±30).
Check for open and short in harness and connector between terminal ECT cruise
control ECU and electronically controlled transmission solenoid(See page
IN±30).
VoltageGear Position
BE±188± BODY ELECTRICAL SYSTEMCRUISE CONTROL SYSTEM