TOYOTA PRIUS 2001 Service Repair Manual

± 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.

F12685
ECU±IG12
W±B20
GND1 IG1
Relay FL Block No. 2
BUZZER Ignition Switch
83W
2 1G
4BZ
W±G
B11 6
Battery
IDB12
B10 13
B±YJ/C
J1
J/C J11
J/C 2D 2B
2I
2K2H
2
3 1
58
AM1
31 2
W±B B±Y
Instrument Panel J/B
IE A
AW±B17 MAIN
B±GFL Block No. 1
1
1
1DC/DC
F13F11
J15
6 Brake Warning Buzzer
GND2 GND4 GND3
B11
B10 IA2
W±B W±BD
E
J14 GBrake ECU
B±Y
A
± DIAGNOSTICSANTI±LOCK BRAKE SYSTEM WITH EBD & RBS
DI±449
2001 PRIUS (RM778U)
Brake Warning Buzzer Circuit
CIRCUIT DESCRIPTION
The brake warning buzzer sounds while the accumulator pressure is abnormally low.
WIRING DIAGRAM
DI29H±07

F02192
1
2
(+) (±)
DI±450
± DIAGNOSTICSANTI±LOCK BRAKE SYSTEM WITH EBD & RBS
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 buzzer.
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 brake warning buzzer sounds ºONº and ºOFFº with the TOYOTA hand±held tester.
OK Check and replace brake ECU.
NG
2 Check brake warning buzzer.
PREPARATION:
Disconnect the brake warning buzzer connector.
CHECK:
Apply battery positive voltage to the terminals 1 and 2 of
BRAKE warning buzzer connector, check that the brake warn-
ing buzzer sounds.
NG Replace brake warning buzzer.
OK

± DIAGNOSTICSANTI±LOCK BRAKE SYSTEM WITH EBD & RBS
DI±451
2001 PRIUS (RM778U)
3 Check for open and short circuit in harness and connector between brake ECU
and brake warning buzzer (See page IN±41).
NG Repair or replace harness or connector.
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

± DIAGNOSTICSANTI±LOCK BRAKE SYSTEM WITH EBD & RBS
DI±453
2001 PRIUS (RM778U)
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.

F12687
DLC3
2DTs 4
Ts
8
4 CG14ID1GR±G
B11
W±B
AJ11
J/C
A
ID
C Instrument Panel J/BBrake ECU
J16
J/C
J24
J/CB
W±B W±B
A2K 8 3
GR±G GR±G
B DI±454
± DIAGNOSTICSANTI±LOCK BRAKE SYSTEM WITH EBD & RBS
2001 PRIUS (RM778U)
Ts Terminal Circuit
CIRCUIT DESCRIPTION
The sensor check circuit detects abnormalities in the speed sensor signal which cannot be detected by the
DTC check.
Connecting terminals Ts and CG of the DLC3 starts the check.
WIRING DIAGRAM
DI29J±12