2001 TOYOTA PRIUS relay

F12681
Brake ECU
B2
2 6
AA 1
1 ABS
No. 2
Engine Room J/B22
2 2
22
14
22
Y 1
3 FL
Block No. 12
2
J1
J/CL±O
5IA2
LG±R
13R1+
R2+ Y±B
W±L F12
IE2 G±W W±L
Battery 1B
6
H6 H6
B±G 1K
Hydraulic Brake
Booster7
W±BY±G14
3Y±G
MR2MR1
MTT
MT+
MT± 29
27
28
18 ABS
No. 3
FL
Block No. 2B
1K
F13H5
H6
H5
H5
H5
W±B W±B
AAY±B
B11
B13
B10
B13
B10
B10
B10
J7
J/CEngine
Room
R/B No. 2 Hydro
Motor
Relay
No. 2 Hydro
Motor
Relay
No. 1 1
23
43
4 2 1
G
MAIN DI±422
± DIAGNOSTICSANTI±LOCK BRAKE SYSTEM WITH EBD & RBS
2001 PRIUS (RM778U)
WIRING DIAGRAM

± DIAGNOSTICSANTI±LOCK BRAKE SYSTEM WITH EBD & RBS
DI±423
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 3, in case
of not using TOYOTA hand±held tester.
1 Check hydro motor relay operation.
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 the operation sound of the hydro motor relays individually when operating it with the TOYOTA hand±
held tester.
OK:
The operation sound of the hydro motor relay should be heard.
NG Go to step 3.
OK
2 Check for short circuit in harness and connector between MTT of hydraulic
brake booster and brake ECU (See page IN±41).
NG Repair or replace harness or connector.
OK
Check and replace brake ECU.

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.

F12678
Ignition SwitchFL Block No. 1
BatteryB±Y
2 4
W±B
W±B
W±B J15
6 1
IG1
GND3
GND1 GND4 DC/DC
AM1
ECU±IG
IDJ/C
A
A AW±B
GND2
B10 F131
12
2B 1 B±G
IEBrake ECU
817 W±GW
Instrument Panel J/B31 2H 2I 2D
2KF11
FL
Block
No. 2B11 B11
B11
B10
J1
J/C J11
J/C6
68 J14
213
35
IG1
RelayB±Y
B±Y
W±BE D
MAIN
± DIAGNOSTICSANTI±LOCK BRAKE SYSTEM WITH EBD & RBS
DI±435
2001 PRIUS (RM778U)
DTC C1257/57 Power Supply Drive Circuit
CIRCUIT DESCRIPTION
DTC No.DTC Detecting ConditionTrouble Area
C1257/57
After turning the ignition switch ON, open or short circuit in
circuit of power supply drive system inside ECU continues
for more than 1.5 sec.
Battery

Power source circuit
WIRING DIAGRAM
DI29D±07

F12678
Ignition SwitchFL Block No. 1
BatteryB±Y
2 4
W±B
W±B
W±B J15
6 1
IG1
GND3
GND1 GND4 DC/DC
AM1
ECU±IG
IDJ/C
A
A AW±B
GND2
B10 F131
12
2B 1 B±G
IEBrake ECU
817 W±GW
Instrument Panel J/B31 2H 2I 2D
2KF11
B11 B11
B11
B10
J1
J/C J11
J/C6
68 J14
213
35
IG1
RelayB±Y
B±Y
W±BE D
FL
Block
No. 2
MAIN
± DIAGNOSTICSANTI±LOCK BRAKE SYSTEM WITH EBD & RBS
DI±439
2001 PRIUS (RM778U)
DTC Always ON Malfunction in ECU
CIRCUIT DESCRIPTION
DTC No.DTC Detecting ConditionTrouble Area
Always ON
Either of the following 1. or 2. is detected:
1. ECU connectors are disconnected from ECU
2. There is a malfunction in ECU internal circuit
Battery

Charging system

Power source circuit

Brake ECU
HINT:
There is a case that TOYOTA hand±held tester cannot be used when ECU is abnormal.
WIRING DIAGRAM
DI7OQ±01

DI±440
± DIAGNOSTICSANTI±LOCK BRAKE SYSTEM WITH EBD & RBS
2001 PRIUS (RM778U)
INSPECTION PROCEDURE
1 Check that brake ECU connectors are securely connected to brake ECU.
NO Connect connectors to brake ECU.
YES
2 Is DTC output?
Check DTC on page DI±353.
YES Repair circuit indicated by output code.
NO
3 Is normal code displayed?
YES Check ABS solenoid relay. Check for short cir-
cuit in harness and connector between ABS so-
lenoid relay and DLC3 (See page IN±41).
NO
4 Does ABS warning light go off?
YES Check for open or short circuit in harness and
connector between ECU±IG fuse and brake ECU
(See page IN±41).
NO

F12444
ON
WA
B11
± DIAGNOSTICSANTI±LOCK BRAKE SYSTEM WITH EBD & RBS
DI±441
2001 PRIUS (RM778U)
5 Check battery positive voltage.
CHECK:
Check the battery positive voltage.
OK:
Voltage: 10 ± 14 V
NG Check and repair charging system (See page
HV±39).
OK
6 Check operation of the ABS warning light.
In case of using the TOYOTA hand±held tester:
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 by the TOYOTA
hand±held tester.
In case of not using the TOYOTA hand±held tester:
(a) Disconnect the connector (B11) from the brake ECU.
(b) Using service wire, connect terminal WA of brake ECU
harness side connector and body ground.
(c) Turn the ignition switch ON.
OK:
ABS warning light goes off.
OK Check and replace brake ECU.
NG
Check for short circuit in harness and connector between combination meter and brake ECU,
combination meter and DLC3 (See page IN±41).
Check ABS solenoid relay circuit (See page DI±376).