2001 TOYOTA PRIUS Service Repair Manual

F12663
(+) (±)
Engine Room R/B No. 2LOCK
1
1
F00044
1
2
3 4
(+) (±) Continuity1 2
3 4
1
2
3 4 Open
Continuity
DI±424
± DIAGNOSTICSANTI±LOCK BRAKE SYSTEM WITH EBD & RBS
2001 PRIUS (RM778U)
3 Check voltage between terminal 1 of engine room R/B No. 2 (for hydro motor re-
lays) and body ground.
PREPARATION:
Remove the hydro motor relay No. 1 and No. 2 from the engine
room R/B No. 2.
CHECK:
Measure voltage between terminal 1 of engine room R/B No. 2
(for hydro motor relays) and body ground.
OK:
Voltage: 10 ± 14 V
NG Check and repair harness or connector.
OK
4 Check hydro motor relay.
CHECK:
Check continuity between each pair of terminal of motor relay.
OK:
Terminals 3 and 4Continuity
(Reference value *)
Terminals 1 and 2Open
* Reference value:
Hydro motor relay No. 1 62 W
Hydro motor relay No. 2 54 W
CHECK:
(a) Apply battery positive voltage between terminals 3 and 4.
(b) Check continuity between terminals.
OK:
Terminals 1 and 2Continuity
NG Replace hydro motor relay.
OK

F12412
Relay
No. 1
2
Brake ECU
MTT Motor
RelayRelay
No. 2 Engine Room R/B No. 2
MTT
2
BM1BM2
± DIAGNOSTICSANTI±LOCK BRAKE SYSTEM WITH EBD & RBS
DI±425
2001 PRIUS (RM778U)
5 Check continuity between each terminal 2 of engine room R/B No. 2 (for hydro
motor relay) and terminal MTT of brake ECU.
CHECK:
(a) Check continuity betwee terminal 2 of engine room R/B
No. 2 (for hydro motor relay No. 1) and terminal MTT of
brake ECU.
(b) Check continuity between terminal 2 of engine room R/B
No. 2 (for hydro motor relay No. 2) and terminal MTT of
brake ECU.
OK:
Continuity
HINT:
There is resistance of 33 ± 3 W between terminals BM1or BM2
and MTT of the hydraulic brake booster.
NG Repair or replace harness, connector or hy-
draulic brake booster.
OK
6 Check for open and short circuit in harness and connector between hydro motor
relay No. 1 and No. 2 and brake ECU (See page IN±41).
NG Repair or replace harness or connector.
OK
Check and replace brake ECU.

F12682
High Pressure
Switch
H5
H6 Hydraulic Brake Booster
W±B W±B W±B 5
A 1
IE GR
J1
J/C Y±R 4
49 B1011Brake ECU
PL PH
B13 H5
H6J7
J/C
A A PL PH
PLG PHG
Low Pressure
SwitchW±B DI±426
± DIAGNOSTICSANTI±LOCK BRAKE SYSTEM WITH EBD & RBS
2001 PRIUS (RM778U)
DTC C1254/54 Pressure Switch Circuit
CIRCUIT DESCRIPTION
DTC No.DTC Detecting ConditionTrouble Area
C1254/54
Either of the following 1. or 2. is detected:
1. After turning the ignition switch ON, short or open circuit
in pressure switch (PL) continued for more than 1 sec.
2. After turning the ignition switch ON open in pressure
switch (PH) continued for more than 1 sec.

Pressure switch (PH or PL)

Pressure switch circuit
WIRING DIAGRAM
DI6AC±02

F12668
LOCK
PLG PL
H9
± DIAGNOSTICSANTI±LOCK BRAKE SYSTEM WITH EBD & RBS
DI±427
2001 PRIUS (RM778U)
INSPECTION PROCEDURE
1 Check pressure switch (PL) resistance.
PREPARATION:
(a) Disconnect the connector (H9) from the hydraulic brake
booster.
(b) With ignition switch OFF, depress the brake pedal more
than 40 times to decrease the accumulator pressure.
HINT:
When a pressure in power supply system is released, reaction
force becomes heavy and stroke becomes shorter.
CHECK:
Measure resistance between terminals PL and PLG of hydrau-
lic brake booster connector.
OK:
Resistance: 5.1 ± 6.3 kW
HINT:
After inspection, connect the connector and clear the DTC (See
page DI±353).
NG Replace hydraulic brake booster assembly.
OK

F12413
LOCKPHG PH
H8
DI±428
± DIAGNOSTICSANTI±LOCK BRAKE SYSTEM WITH EBD & RBS
2001 PRIUS (RM778U)
2 Check pressure switch (PH) resistance.
PREPARATION:
(a) Disconnect the connector (H8) from the hydraulic brake
booster.
(b) With ignition switch OFF, depress the brake pedal more
than 40 times to decrease the accumulator pressure.
HINT:
When a pressure in power supply system is released, reaction
force becomes heavy and stroke becomes shorter.
CHECK:
Measure resistance between terminals PH and PHG of hydrau-
lic brake booster connector.
OK:
Resistance: 0.9 ± 1.1 kW
HINT:
After inspection, connect the connector and clear the DTC (See
page DI±353).
NG Replace hydraulic brake booster assembly.
OK
3 Check for open and short circuit in harness and connector between each pres-
sure switch and brake ECU (See page IN±41).
NG Repair or replace harness or connector.
OK
Check and replace brake ECU.