TOYOTA SUPRA 1995 Service Repair Manual

DTC 61 TRAC ECU Communication Circuit Malfunction
CIRCUIT DESCRIPTION
DTC No.Diagnostic Trouble Code Detecting ConditionTrouble area
61

Open or short in THFA, TRCO circuit

ABS & TRAC ECU

TRAC ECU
Either of the following (1) or (2) continues for
more than 8 sec.:
(1) Vehicle speed signal of 4 wheels is less
than 1 km/h (1 mph) when TRCO signal is
input.
(2) Voltage of ABS & TRAC ECU terminal
THFA is 0 V when TRCO signal is not
input.
BR±102± BRAKE SYSTEMANTI±LOCK BRAKE SYSTEM (ABS)

Check voltage between terminals THFA, TRCO of ABS & TRAC ECU and
body ground.
Check and replace ABS & TRAC ECU.
Disconnect ABS & TRAC ECU connector.
Measure voltage between terminals THFA, TRCO
of ABS & TRAC ECU connector and body ground
when ignition switch is turned ON.
Voltage: See step 1.
Check voltage between terminals THFA, TRCO of ABS & TRAC ECU and
body ground with ABS & TRAC ECU connector is disconnected.
Remove ABS & TRAC ECU with connectors still
connected.
Measure voltage between terminals THFA,
TRCO of ABS & TRAC ECU and body ground
when ignition switch is turned ON.
Voltage:
TRCO: 7 Ð 12 V
THFA: About 5 V (Pulse)
Check and replace ABS & TRAC ECU.
Check for open and short in harness and connector between ABS & TRAC
ECU and TRAC ECU (See page IN±30).
Check and replace or connector.
Check and replace TRAC ECU.
INSPECTION PROCEDURE.
± BRAKE SYSTEMANTI±LOCK BRAKE SYSTEM (ABS)BR±103

DTC 62 TRAC Vehicle Speed Malfunction
DTC No.Diagnostic Trouble Code Detecting ConditionTrouble area
62
ECUAt vehicle speed of 10 km/h (6 mph) or more,
pulses are not input for 5 sec.
HINT: When DTC Nos.31 Ð 36 are recorded in memory, DTC No.62 is not recorded.
Go to relevant DTC chart.
Replace ABS & TRAC ECU.
CIRCUIT DESCRIPTION
INSPECTION PROCEDURE
Are there any other codes (Besides DTC No.62) being output?
BR±104± BRAKE SYSTEMANTI±LOCK BRAKE SYSTEM (ABS)

Stop Light Switch Circuit
CIRCUIT DESCRIPTION
WIRING DIAGRAM
The stop light switch senses whether the brake pedal is depressed or released, and spends a signal
to the ECU.
± BRAKE SYSTEMANTI±LOCK BRAKE SYSTEM (ABS)BR±105

INSPECTION PROCEDURE
Remove ABS & TRAC ECU with connectors still
connected.
Measure voltage between terminals STP of ABS
(& TRAC) ECU and body ground when brake ped-
al is depressed
Voltage: 8 Ð 14 V
Check operation of stop light.
Check voltage between terminal STP of ABS (& TRAC) ECU and
body ground.
Remove ABS & TRAC ECU with connectors
still connected.
Measure voltage between terminals STP of
ABS (& TRAC) ECU and body ground when
brake pedal is depressed.
Voltage: 8 Ð 14 V
Repair stop light circuit.
Repair or replace harness or connector.
Proceed to next circuit inspection shown on
problem symptoms chart (See page BR±64).
Check for open in harness and connector between ABS (& TRAC)
ECU and stop light switch (See page IN±30).
Check and replace ABS (& TRAC) ECU.
Check the stop light lights up when brake pedal is depressed and turns off when brake pedal is
released. BR±106
± BRAKE SYSTEMANTI±LOCK BRAKE SYSTEM (ABS)

ABS Warning Light Circuit
CIRCUIT DESCRIPTION
If the ECU detects trouble, it lights the ABS warning light while at the same time prohibiting ABS control.
At this time, the ECU records a diagnostic trouble code in memory.
After removing the short pin of the DLC1, connect terminals Tc and E1 of the DLC1 or DLC2 to make the
ABS warning light to blink and output the diagnostic trouble code.
± BRAKE SYSTEMANTI±LOCK BRAKE SYSTEM (ABS)BR±107

Check ABS warning light.
Disconnect the connectors from solenoid relay.
Check continuity between each terminal of ABS
solenoid relay shown below.
Replace bulb or combination meter assembly.
See Combination Meter Troubleshooting on page BE±43.
(1) Apply battery positive voltage between termi-
nals (A9) 1 and (A8) 3.
(2) Check continuity between each terminal of
ABS solenoid relay shown below.
Connect the
test lead to terminal (A9)4 and the
 lead to the terminal (A9)5. Check continuity be-
tween the terminals.
Continuity
If there is no continuity, connect the  test lead to
terminal (A9)4 and the
lead to terminal (A9)5.
Recheck continuity between terminals.
Terminals (A9) 5 and (A9) 6
Terminals (A9) 2 and (A9) 5
Open
Continuity
Continuity
Open
Terminals (A9) 1 and (A8) 3
Terminals (A9) 5 and (A9) 6
Terminals (A9) 2 and (A9) 5
Continuity
(Reference value 80
)
Replace ABS control relay.
Check ABS solenoid relay.
Repair or replace and check for open in harness and connector between DLC1 and ABS solenoid
relay and body ground (See page IN±30).Repair or replace and check for open in harness and connector between DLC1 and ABS solenoid
relay and body ground (See page IN±30).
INSPECTION PROCEDURE (w/o TRAC)
Perform troubleshooting in accordance with the chart below for each trouble symptom.
 


ABS warning light does not light up
 
 Go to step [1]
 


ABS warning light remains on 
 Go to step [3]
BR±108± BRAKE SYSTEMANTI±LOCK BRAKE SYSTEM (ABS)

Is diagnostic trouble code output?
Repair circuit indicated by the code output.
Do diagnostic trouble code check on page BR±54.
Does ABS warning light go off if short pin is removed?
Check ABS solenoid relay (See step No.2).
Repair ABS control relay.
Check for short in harness and connector be-
tween warning light and DLC1 and ECU (See
page IN±30).
Repair or replace and check for short in harness
and connector between DLC1 and ABS solenoid
relay (See page IN±30).
± BRAKE SYSTEMANTI±LOCK BRAKE SYSTEM (ABS)BR±109

Check ABS warning light.
Disconnect the connectors from R/B No.5.
Check continuity between each terminal of ABS
solenoid relay shown below.
Replace bulb or combination meter assembly.
1. Apply battery positive voltage between ter±
minals 4 and 6.
2. Check continuity between each terminal of
ABS solenoid relay shown below.
Terminals 2 and 3
Terminals 1 and 3
Open
Continuity
Continuity
Open
Terminals 4 and 6
Terminals 2 and 3
Terminals 1 and 3
Continuity
(Reference value 80
)
Replace ABS solenoid relay.
Check ABS solenoid relay.
Repair or replace and check for open in harness and connector between DLC1 and ABS solenoid
relay and body ground (See page IN±30).
Connect the
test lead to terminal 5 and the 
lead to the terminal 3. Check continuity between
the terminals.
Continuity
If there is no continuity, connect the  test lead to
terminal 5 and the
lead to terminal 3. Recheck
continuity between terminals.
See Combination Meter Troubleshooting on page BE±43.
INSPECTION PROCEDURE (w/ TRAC)
Troubleshoot in accordance with the chart below for each trouble symptom.
 ABS warning light does not light up Go to step [1]
 ABS warning light remains on Go to step [3]
BR±110± BRAKE SYSTEMANTI±LOCK BRAKE SYSTEM (ABS)

Is diagnostic trouble code output?
Repair circuit indicated by the code output.
Does ABS warning light go off if short pin is removed?
Do diagnostic trouble code check on page BR±54.
Check for short in harness and connector be-
tween warning light and DLC1 and ECU (See
page IN±30).
Repair or replace and check for short in harness
and connector between DLC1 and ABS solenoid
relay (See page IN±30).
± BRAKE SYSTEMANTI±LOCK BRAKE SYSTEM (ABS)BR±111