2001 TOYOTA PRIUS brake light

F12683
Brake ECU
Instrument Panel J/B GAUGE 4
IH L FL Block No. 1
1
BatteryIgnition Switch
2
2
2K2A18
W
3AM1IP1
AABS
2A14 2B F11
C10
J11
J/CB±W
5WA
W±B W±G
2H 2D DC/DC
B±Y
1
FL Block
No. 2 B±G
F131
B11
1C10
C10L2
10
22
5 1
3
6
87
LCommbination
Mater
2B 6
IDBR MAIN DI±442
± DIAGNOSTICSANTI±LOCK BRAKE SYSTEM WITH EBD & RBS
2001 PRIUS (RM778U)
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 DTC in memory.
Connect terminals Tc and CG of the DLC3 to make the ABS warning light blink and output the DTC.
WIRING DIAGRAM
DI29F±14

± DIAGNOSTICSANTI±LOCK BRAKE SYSTEM WITH EBD & RBS
DI±443
2001 PRIUS (RM778U)
INSPECTION PROCEDURE
HINT:
Troubleshoot in accordance with the chart below for each trouble symptom.
ABS warning light does not light up*1
ABS warning light remains on*2
*1: Start the inspection from step 1 in case of using the TOYOTA hand±held tester and start from step 2 in
case of not using TOYOTA hand±held tester.
*2: After inspection with step 4, start the inspection from step 5 in case of using the TOYOTA hand±held
tester and start from step 6 in case of not using TOYOTA hand±held tester.
1 Check operation of the brake warning light.
PREPARATION:
(a) Connect the TOYOTA hand±held tester to the DLC3.
(b) Turn the ignition switch ON, and push the TOYOTA hand±held tester main switch ON.
(c) Select the ACTIVE TEST mode on the TOYOTA hand±held tester.
CHECK:
Check that ºONº and ºOFFº of the ABS warning light can be shown on the combination meter on the TOYOTA
hand±held tester.
OK Check and replace brake ECU.
NG
2 Check ABS warning light.
See combination meter troubleshooting on page BE±2.
NG Repair bulb or combination meter assembly.
OK

± DIAGNOSTICSANTI±LOCK BRAKE SYSTEM WITH EBD & RBS
DI±445
2001 PRIUS (RM778U)
4 Check that the brake ECU connectors are securely connected to the brake ECU.
NO Connect the connector to the brake ECU.
YES
5 Check operation of the ABS warning light (See step 1).
OK Check and replace brake ECU.
NG
6 Is DTC output?
Check DTC on page DI±353.
YES Repair circuit indicated by the output code.
NO
7 Check ABS solenoid relay (See step 3).
NG Replace ABS solenoid relay.
OK
Check for short circuit in harness and connector between DLC3 and ABS solenoid relay (See
page IN±41).

F12684
Brake Fluid Level
Warning Switch
IG1
Relay FL Block No. 2
Body ECU
Multiplex Communication CircuitR±Y
BrakePKB
E
83
GAUGE5
WJ12
J/C Parking
Brake Switch
2 1
1C10
2A7
LG±R
A 4BRL Brake ECU
W±GB12
6
Battery
IE LBL B12 B1113
R±Y R±Y
R±Y E
J7
J/C
J1
J/C
J11
J/C 2D2B
2H2K
2K5
23 15
2A7 AM1
C10C11C11
143
2
22 2
W±BB±Y
L
BRA A
A
W±BW±B 21 IA2 18
MAIN
B±GFL Block No. 1
111
DC/DC
F13 F11
B8 B8 15 164 Instrument
Panel J/B
LGR GR±B Ignition Switch
Instrument
Panel J/B
Commbination Meter
2B6
IH ID DI±446
± DIAGNOSTICSANTI±LOCK BRAKE SYSTEM WITH EBD & RBS
2001 PRIUS (RM778U)
BRAKE Warning Light Circuit
CIRCUIT DESCRIPTION
The BRAKE warning light lights up when the brake fluid is insufficient, the parking brake is applied or the
EBD is defective.
The BRAKE warning light also lights up when DTC No. C1213/63 or C1259/59 is detected, however, the EBD
is not inhibited in this case.
WIRING DIAGRAM
DI29G±14

± DIAGNOSTICSANTI±LOCK BRAKE SYSTEM WITH EBD & RBS
DI±447
2001 PRIUS (RM778U)
INSPECTION PROCEDURE
HINT:
Start the inspection from step 1 in case of using the TOYOTA hand±held tester and start from step 2 in case
of not using the TOYOTA hand±held tester.
1 Check operation of the BRAKE warning light.
PREPARATION:
(a) Release the parking brake pedal.
(b) Connect the TOYOTA hand±held tester to the DLC3.
(c) Turn the ignition switch ON, and push the TOYOTA hand±held tester main switch ON.
(d) Select the ACTIVE TEST mode on the TOYOTA hand±held tester.
CHECK:
Check that ºONº and ºOFFº of BRAKE warning light can be shown on the combination meter by the TOYOTA
hand±held tester.
OK Check and replace brake ECU.
NG
2 Check parking brake switch circuit (See page BE±2).
NG Repair or replace parking brake switch circuit.
OK
3 Check brake fluid level warning switch circuit (See page BE±2).
NG Repair or replace brake fluid level warning
switch circuit.
OK
4 Is DTC output for ABS ?
Yes Repair circuit indicated by the output code.
No

DI±448
± DIAGNOSTICSANTI±LOCK BRAKE SYSTEM WITH EBD & RBS
2001 PRIUS (RM778U)
5 Check BRAKE warning light.
See combination meter troubleshooting on page BE±2.
NG Repair or replace combination meter.
OK
6 Check multiplex communication system (See page DI±752).
NG Repair or replace multiplex communication cir-
cuit.
OK
Check and replace brake ECU.

F12686
DLC3
2DTc 3
Tc
8
4 CG13ID1 P±B P±B
B11
W±B
AJ11
J/C
A
ID C
Instrument Panel J/BBrake ECU
J16
J/C J26
J/C
J24
J/CP±B P±B
E E
C
W±B W±B
A2K 82
F09678
CG TcDLC3 ON
(+) (±)
DI±452
± DIAGNOSTICSANTI±LOCK BRAKE SYSTEM WITH EBD & RBS
2001 PRIUS (RM778U)
Tc Terminal Circuit
CIRCUIT DESCRIPTION
Connecting terminals Tc and CG of the DLC3 causes the ECU to display the DTC by flashing the ABS warn-
ing light.
WIRING DIAGRAM
INSPECTION PROCEDURE
1 Check voltage between terminals Tc and CG of DLC3.
PREPARATION:
Turn the ignition switch ON.
CHECK:
Measure voltage between terminal Tc and CG of DLC3.
OK:
Voltage: 10 ± 14 V
OK If ABS warning light does not blink even after Tc
and CG are connected, the ECU may be defec-
tive.
NG
DI29I±13

F09679
ON
DLC3 (+) (±)
Ts
CG
± DIAGNOSTICSANTI±LOCK BRAKE SYSTEM WITH EBD & RBS
DI±455
2001 PRIUS (RM778U)
INSPECTION PROCEDURE
1 Check voltage between terminals Ts and CG of DLC3.
CHECK:
(a) Turn the ignition switch ON.
(b) Measure voltage between terminals Ts and CG of DLC3.
OK:
Voltage: 10 ± 14 V
OK If ABS warning light does not blink even after Ts
and CG are connected, the ECU may be defec-
tive.
NG
2 Check for open and short circuit in harness and connector between brake ECU
and DLC3, DLC3 and body ground (See page IN±41).
NG Repair or replace harness or connector.
OK
Check and replace brake ECU.