05–2559

DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM 05J5U–01

DTC B1200 BODY ECU COMMUNICATION STOP

CIRCUIT DESCRIPTION
This DTC is detected when communication between the multiplex network body ECU and gateway ECU
stops for more than 10 seconds.
DTC No. DTC Detection Condition Trouble Area

Instrument panel
anel J/B assy (Body ECU)
B1200 B d ECU communication
Body i ti stops
t

Wire harness

cardiagn.com

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2723

05–2560
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM

WIRING DIAGRAM
T5
Transponder Key Instrument
ECU Assy Panel J/B Assy

Center Connector No. 1 Body ECU

11 11 15
B B
MPX1 4D 4F B5 MPX2
17

A8
A/C Control Assy

Center Connector No. 2

cardiagn.com
8 8 9
GR GR
MPX2+ 5J 5K 1G MPX1
11 17

Engine Room J/B

and Engine Room R/B J6
1 DOME J/C 30
B R R
3M 3 1A ECUB
1 2 B B 6

1 BE1

1 F15 17
W–B
1E GND
FL Block Assy 1
MAIN

Battery IH

B79843

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2724

 05–2561
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM

INSPECTION PROCEDURE
1 INSPECT FUSE (DOME)

(a) Remove the DOME fuse from engine room J/B and engine room R/B.
(b) Measure the resistance.
Standard: Below 1 Ω
NG REPLACE FUSE

OK

2 CHECK WIRE HARNESS (INSTRUMENT PANEL J/B ASSY – BODY GROUND)

Wire Harness Side

(a) Disconnect the 1A and 1E J/B connectors.
(b) Measure the voltage and resistance of the wire harness
1A side connectors.
1E
Instrument Standard:
Instrument
Panel J/B Assy

cardiagn.com
Panel J/B Assy Tester Connection Specified Condition
1A–30 (ECUB) – Body ground 10 to 14 V
1E–17 (GND) – Body ground Below 1 Ω

GND

ECUB

NG REPAIR OR REPLACE HARNESS AND

B79867 CONNECTOR

OK

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2725

05–2562
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM

3 CHECK RESISTANCE OF COMMUNICATION LINE

Wire Harness Side (a) Disconnect the 1G J/B connector.

1G (b) Disconnect the T5, A8 and B5 ECU connectors.
Instrument Panel J/B (c) Measure the resistance between the wire harness side
connectors.
Standard:
Tester Connection Specified Condition
T5–17 (MPX1) – B5–15 (MPX2) Below 1 Ω
A8–11 (MPX2+) – 1G–9 (MPX1) Below 1 Ω
MPX1
Result:
T5
Result Proceed To
Transponder Key ECU Assy
Both are OK A
One is OK B
Both are NG C

cardiagn.com
MPX1
A8
A/C Control Assy

MPX2+
B5
Body ECU

B REPLACE INSTRUMENT PANEL J/B ASSY AND

REPAIR OR REPLACE HARNESS AND CON-
NECTOR

MPX2 C REPAIR OR REPLACE HARNESS AND

CONNECTOR
B79845

REPLACE INSTRUMENT PANEL J/B ASSY (MULTIPLEX NETWORK BODY ECU)

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2726

 05–2563
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM 05J5X–01

DTC B1207 SMART ECU COMMUNICATION STOP

CIRCUIT DESCRIPTION
This DTC is detected when communication between the smart ECU and gateway ECU stops for more than
10 seconds.
DTC No. DTC Detection Condition Trouble Area

Smart ECU
B1207 S
Smart
t ECU communication
i ti stops
t

Wire harness

cardiagn.com

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2727

05–2564
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM

WIRING DIAGRAM

T4 S11
Transmission Control ECU Smart ECU
Center Connector No. 1
8 7 7
GR GR GR
MPX1 II1 4I 4L MPX1
19 31

C10
Combination Meter
Center Connector No. 1
2 2 16
B W B
MPX+ IG1 4C 4L MPX2
24 32

cardiagn.com
J6 Instrument Panel J/B J23
J/C 13 7 J/C
R R R R
1A 1F +B
B B A A 1

Engine
2 W–B
DOME Room J/B and E
1 17
Engine Room R/B

1 3M
12 4L
B Center
Connector
1 BE1
No. 1
5 4H
B
1
W–B
F15 A
MAIN
FL Block Assy J25
J/C
A
W–B

Battery
IH

B79846

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2728

 05–2565
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM

INSPECTION PROCEDURE
1 CHECK OPERATION

(a) With the smart key in your possession, push the lock button on the door outside handle (smart door
lock operation). Check that the smart indicator illuminates or starts blinking.
With the smart key in your possession, touch the inside of the door outside handle (smart door unlock
operation). Check that the smart indicator illuminates or starts blinking.
OK: Smart indicator illuminates or starts blinking.
NG Go to step 3

OK

2 CHECK WIRE HARNESS (SMART ECU – BODY GROUND)

Wire Harness Side (a) Disconnect the S11 ECU connector.

S11 (b) Measure the resistance and voltage of the wire harness
Smart ECU side connector.

cardiagn.com
Standard:
Tester Connection Specified Condition
S11–1 (+B) – Body ground 10 to 14 V
S11–17 (E) – Body ground Below 1 Ω

+B E
B79987

NG REPAIR OR REPLACE HARNESS AND

CONNECTOR

OK

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2729

05–2566
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM

3 CHECK RESISTANCE OF COMMUNICATION LINE

Wire Harness Side (a) Disconnect the S11 and T4 ECU connectors.
(b) Disconnect the C10 meter connector.
S11
(c) Measure the resistance of the wire harness side connec-
Smart ECU tors.
Standard:
Tester Connection Specified Condition
S11–31 (MPX1) – T4–19 (MPX1) Below 1 Ω
S11–32 (MPX2) – C10–24 (MPX+) Below 1 Ω

Result:
MPX1 MPX2 Result Proceed To
Both are OK A
T4 One is OK B
Transmission Control ECU Both are NG C

cardiagn.com
MPX1

C10
Combination Meter

B REPLACE SMART ECU AND REPAIR OR

REPLACE HARNESS AND CONNECTOR

MPX+ C REPAIR OR REPLACE HARNESS AND

B79848
CONNECTOR

REPLACE SMART ECU

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2730

 05–2567
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM 05J5Z–01

DTC B1210 POWER SOURCE CONTROL ECU

COMMUNICATION STOP

CIRCUIT DESCRIPTION
This DTC is detected when communication between the power source control ECU and gateway ECU stops
for more than 10 seconds.
DTC No. DTC Detection Condition Trouble Area

Power source control ECU

B1210 P
Power source control
t l ECU communication
i ti stops
t

Wire harness

cardiagn.com

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2731

05–2568
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM

WIRING DIAGRAM
C10 P6
Combination Meter Power Source Control ECU
Center Connector No. 2
3 13 13
GR P GR
MPX– IG2 5D 5G MPX1
25 7

G1
Gateway ECU
Center Connector No. 2
8 8
GR B
MPD1 5C 5G MPX2
3 24

Center Connector No. 2 Center Connector No. 2

cardiagn.com
12 7 8 15
B W
IG 5C 5L 5L 5H
1

Center
W
O Connector No. 1
8 8
R R
4G 4J AM1
33
7 7
1 3D B B
4G 4J IG1D
34
2 Engine
DC/DC
1 Room J/B
1 1J 3 1J 1 1B 7 1L
1 3M

B AM1

ECU– Instrument
1 BE1 2 5
IG Panel J/B
IG1
B Relay
1
1 3
F15
MAIN
FL Block Assy 17 1E

B GND2
W–B 6

Battery IH
To Body Ground

B79849

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2732

 05–2569
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM

INSPECTION PROCEDURE
1 CHECK OPERATION

(a) Without depressing the brake pedal, push the power switch repeatedly. Check that the power modes
change between OFF, ON (ACC) and ON (IG) alternately.
OK: Smart indicator illuminates or starts blinking according to power modes.
NG Go to PUSH BUTTON START SYSTEM
(See page 05–2429)

OK

2 CHECK WIRE HARNESS (POWER SOURCE CONTROL ECU – BODY GROUND)

Wire Harness Side (a) Disconnect the P6 ECU connector.

P6 (b) Measure the resistance and voltage of the wire harness
Power Source Control ECU side connector.
Standard:

cardiagn.com
Tester Connection Condition Specified Condition
P6–34 (IG1D) – Power switch
Body ground 1: OFF → 2: ON (IG) 1: 0 V → 2: 10 to 14 V
P6–33 (AM1) –
GND2 AM1 IG1D Body ground
Constant 10 to 14 V
B79987
P6–6 (GND2) –
Constant Below 1 Ω
Body ground

NG REPAIR OR REPLACE HARNESS AND

CONNECTOR

OK

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2733

05–2570
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM

3 CHECK RESISTANCE OF COMMUNICATION LINE

Wire Harness Side

(a) Disconnect the P6 and G1 ECU connectors.
(b) Disconnect the C10 meter connector.
(c) Measure the resistance between the wire harness side
P6
Power Source Control ECU connectors.
Standard:
Tester Connection Specified Condition
P6–7 (MPX1) – C10–25 (MPX–) Below 1 Ω
P6–24 (MPX2) – G1–3 (MPD1) Below 1 Ω

Result:
Result Proceed to
MPX1 MPX2
Both are OK A
One is OK B
G1
Both are NG C
Gateway ECU

cardiagn.com
MPD1

C10
Combination Meter

B REPLACE POWER SOURCE CONTROL ECU

AND REPAIR OR REPLACE HARNESS AND
CONNECTOR

C REPAIR OR REPLACE HARNESS AND

MPX– CONNECTOR
B79851

REPLACE POWER SOURCE CONTROL ECU

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2734

 05–2571
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM 05J61–01

DTC B1214 DOOR SYSTEM COMMUNICATION BUS

MALFUNCTION (+B SHORT)

DTC B1215 DOOR SYSTEM COMMUNICATION BUS

MALFUNCTION (GND SHORT)

CIRCUIT DESCRIPTION
DTCS B1214 and B1215 are detected when +B and body ground is short–circuited on the door system com-
munication bus. Detecting this condition will disable the door system communication bus (BEAN) and output
some diagnosis codes.
DTC NO. DTC Detection Condition Trouble Area

Body ECU

Smart ECU*

Power source control ECU

Radio receiver amplifier
Door system communication circuit and +B battery system
B1214
Transmission control ECU
short

cardiagn.com

A/C amplifier

Combination meter

Transponder key ECU (Immobilizer ECU)

Wire harness

Body ECU

Smart ECU*

Power source control ECU

Radio receiver amplifier
B1215 Door system communication circuit and body ground short
Transmission control ECU

A/C amplifier

Combination meter

Transponder key ECU (Immobilizer ECU)

Wire harness

*: w/ Smart entry system

WIRING DIAGRAM
The wiring diagram is shown on the next page.

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2735

05–2572
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM

*1: w/ Smart Entry System

*2: w/o Smart Entry System
G1
P6
Center Connector No. 2 Gateway ECU
Power Source Control ECU
8 8
GR 7 24 B GR 3
MPX1 MPX2 5G 5C MPD1

C10
Center Connector No. 2 Combination Meter
13 13 3 2
P GR B
5G 5C IG2 MPX– MPX+ IG1
25 24

W*2
Center Connector No. 1
16 2
GR*1 B*1 W
MPX1 MPX2 4L 4C
31 32
S11

cardiagn.com
Smart ECU*1
B 12
MPD2
GR
15 B5
MPX2
Center Connector No. 1
Body ECU 4 5C
7 4L 11 4F MPX1 Center
17 Connector
No. 2
7 4I 11 4D 9 1G 13 5J
T5
B
Transponder
GR Key ECU
17
MPX1
B
8 II1 MPX2

T4 16 GR
GR Transmission A8
19 Control ECU A/C Control Assy 3
MPX1 MPX+
GR
MPX2 MPX2+
18 11
B

9 II1 2 4D 8 5K
Center Center
Connector Connector
No. 1 No. 2
14 4I 8 5J

B GR
B79237

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2736

 05–2573
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM

INSPECTION PROCEDURE
1 CHECK DIAGNOSTIC TROUBLE CODE (A ECU)

(a) Disconnect the A ECU connector and check for DTCs B1214 and B1215.

Gateway ECU

Communication Circuit

cardiagn.com
Communication Circuit Communication Circuit Communication Circuit

A ECU B ECU C ECU

B79627

OK: DTCs B1214 and B1215 are not output.

NOTICE:
Disconnect the connectors one by one. Reconnect the connector before starting the next check.
HINT:

The A ECU in the door system bus represents the power source control ECU.

If the result is as specified, the disconnected A ECU (power source control ECU) is malfunctioning.
NG Go to step 2

OK

REPLACE A ECU

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2737

05–2574
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM

2 CHECK DIAGNOSTIC TROUBLE CODE (B ECU)

(a) Disconnect the A ECU and B ECU connectors and check for DTCs B1214 and B1215.

Gateway ECU

Communication Circuit

Communication Circuit Communication Circuit Communication Circuit

cardiagn.com
A ECU B ECU C ECU

B79628

OK: DTCs B1214 and B1215 are not output.

NOTICE:
Disconnect the connectors one by one. Reconnect the connector before starting the next check.
HINT:

The B ECU in door system bus represents one of the following: combination meter, smart ECU*, trans-
mission control ECU, transponder key ECU or body ECU.

If the result is as specified, the disconnected B ECU (one of the ECUs from the above list) or the wire
harness between the A ECU and B ECU is malfunctioning.
*: w/ Smart entry system
NG Go to step 4

OK

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2738

 05–2575
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM

3 CHECK WIRE HARNESS BETWEEN A ECU AND B ECU

(a) Disconnect the B ECU connectors and check for DTCs B1214 and B1215.

Gateway ECU

Communication Circuit

Communication Circuit Communication Circuit Communication Circuit

cardiagn.com
A ECU B ECU C ECU

B51831 B79912

OK: DTCs B1214 and B1215 are not output.

NOTICE:
Disconnect the connectors one by one. Reconnect the connector before starting the next check.
HINT:
If the result is as specified, the wire harness between the A ECU and B ECU is functioning normally but the
disconnected B ECU is malfunctioning.
NG REPAIR OR REPLACE BETWEEN WIRE
HARNESS OF A ECU AND B ECU

OK

REPLACE B ECU

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2739

05–2576
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM

4 CHECK DIAGNOSTIC TROUBLE CODE (C ECU)

(a) Disconnect the B ECU and C ECU connectors and check for DTCs B1214 and B1215.
Gateway ECU

Communication Circuit

Communication Circuit Communication Circuit Communication Circuit

cardiagn.com
A ECU B ECU C ECU

B79630

OK: DTCs B1214 and B1215 are not output.

NOTICE:
Disconnect the connectors one by one. Reconnect the connector before starting the next check.
HINT:

The C ECU in the door system bus represents the A/C control assy.

If the result is as specified, the disconnected C ECU (A/C control assy) or the wire harness between
the B ECU and C ECU is malfunctioning.
NG Go to step 6

OK

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2740

 05–2577
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM

5 CHECK WIRE HARNESS BETWEEN B ECU AND C ECU

(a) Disconnect the C ECU connector and check for DTCs B1214 and B1215.

Gateway ECU

Communication Circuit

Communication Circuit Communication Circuit

cardiagn.com
Communication Circuit

A ECU B ECU C ECU

B79631

OK: DTCs B1214 and B1215 are not output.

NOTICE:
Disconnect the connectors one by one. Reconnect the connector before starting the next check.
HINT:
If the result is as specified, the wire harness between the B ECU and C ECU is functioning normally but the
disconnected C ECU malfunctioning.
NG REPAIR OR REPLACE BETWEEN WIRE
HARNESS OF B ECU AND C ECU

OK

REPLACE C ECU

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2741

05–2578
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM

6 CHECK WIRE HARNESS BETWEEN GATEWAY ECU AND A ECU OR C ECU

(a) Check for a short–circuit in +B or body ground.

Gateway ECU

Communication Circuit

Communication Circuit Communication Circuit Communication Circuit

cardiagn.com
A ECU B ECU C ECU

B79632

(1) Disconnect the A ECU, C ECU and gateway ECU connectors.

(2) Measure the voltage and resistance of the wire harness side connectors.
Standard:
Tester Connection Specified Condition
A ECU connector/gateway ECU connector – body ground 0V
C ECU connector/gateway ECU connector – body ground 0V
A ECU connector/gateway ECU connector – body ground 10 kΩ or higher
C ECU connector/gateway ECU connector – body ground 10 kΩ or higher
HINT:

The A ECU in the door system bus represents the power source control ECU.

The C ECU in the door system bus represents the A/C control assy.
NG REPAIR OR REPLACE BETWEEN WIRE
HARNESS OF GATEWAY ECU AND A ECU OR C
ECU

OK

REPLACE NETWORK GATEWAY ECU

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2742

 05–2579
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM 05J63–01

DTC B1248 AVC–LAN COMMUNICATION IMPOSSIBLE

CIRCUIT DESCRIPTION
This DTC is detected when communication is impossible between the radio and player ECU and gateway
ECU.
DTC No. DTC Detection Condition Trouble Area

Radio and player

layer ECU
B1248 AVC LAN communication
AVC–LAN i ti iis iimpossible
ibl

Wire harness

WIRING DIAGRAM

G1

cardiagn.com
Gateway ECU Center Connector No. 2 Multi–display Radio and Player ECU

6 6 4 18 9
B B P
GTX+ 5C 5E M13 TX1+ TX2+ M13 R5 TX+
6

7 7 5 19 10
W W W
GTX– 5C 5E M13 TX1– TX2– M13 R5 TX–
21

B79852

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2743

05–2580
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM

INSPECTION PROCEDURE
1 CHECK OPERATION

(a) Check that the radio and player switch can operate normally.
OK: Radio and player switch can operate normally.
NG Go to AUDIO SYSTEM (See page 05–1757)

OK

2 CHECK RESISTANCE OF COMMUNICATION LINE

Wire Harness Side (a) Disconnect the R5, M13 and G1 ECU connectors.
(b) Measure the resistance between the wire harness side
R5 connectors.
Radio and Player ECU Standard:
Tester Connection Specified Condition
Below 1 Ω

cardiagn.com
R5–9 (TX+) – M13–18 (TX2+)
TX–
R5–10 (TX–) – M13–19 (TX2–) Below 1 Ω
M13–4 (TX1+) – G1–6 (GTX+) Below 1 Ω
M13–5 (TX1–) – G1–21 (GTX–) Below 1 Ω
TX+

M13
TX1+ Multi–display TX1–

TX2+ TX2–
G1
Gateway ECU

GTX– GTX+
B79854 NG REPAIR OR REPLACE HARNESS AND
CONNECTOR

OK

REPLACE RADIO AND PLAYER ECU

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2744

 05–2581
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM 05J66–01

DTC B1260 TRANSMISSION CONTROL ECU

COMMUNICATION STOP

CIRCUIT DESCRIPTION
This DTC is detected when communication between the transmission control ECU and gateway ECU stops
for more than 10 seconds.
DTC No. DTC Detection Condition Trouble Area

Transmission control ECU

B1260 T
Transmission
i i control
t l ECU communication
i ti stops
t

Wire harness

cardiagn.com

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2745

05–2582
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM

WIRING DIAGRAM
S11 T4
Smart ECU Center Connector No. 1 Transmission Control ECU

7 7 8
GR GR GR
MPX1 4L 4I II1 MPX1
31 19

T5
Transponder Key ECU Assy

2 14 9
GR B B
MPX2 4D 4I II1 MPX2
16 18

J3
J/C

cardiagn.com
1
L L L 1
BE1 +B
A A

H16
B O Hybrid Vehicle
MREL
4 Control ECU
E1
15

1 3M 4 3J 2 3J W–B
1 BE1

13 J13

IGCT Engine J/C

B
1 Relay Room
P/I 13 J12
2 J/B
1
F15 2
HEV
FL 1
MAIN W–B
Block
Assy
1 3A 1 3K 3 3J
8 EB1

W
W–B
W–B

Battery EE EF

B79855

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2746

 05–2583
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM

INSPECTION PROCEDURE
1 INSPECT FUSE (HEV)

(a) Remove the HEV fuse from the engine room J/B.
(b) Measure the resistance.
Standard: Below 1 Ω
NG REPLACE FUSE

OK

2 CHECK WIRE HARNESS (TRANSMISSION CONTROL ECU – BODY GROUND)

Wire Harness Side (a) Disconnect the T4 ECU connector.

T4 (b) Measure the voltage and resistance between the wire
Transmission Control ECU harness side connector.
Standard:

cardiagn.com
Tester Connection Condition Specified Condition
Power switch
T4–1 (+B) – Body ground
1: OFF → 2: ON (IG) 1: 0 V → 2: 10 to 14 V
T4–15 (E1) – Body ground Constant Below 1 Ω
+B E1
B79989 NG REPAIR OR REPLACE HARNESS AND
CONNECTOR

OK

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2747

05–2584
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM

3 CHECK RESISTANCE OF COMMUNICATION LINE

(a) Disconnect the T4, T5 and S11 ECU connectors.

Wire Harness Side
(b) Measure the resistance of the wire harness side connec-
tors.
T4 Standard:
Transmission Control ECU
Tester Connection Specified Condition
T4–19 (MPX1) – S11–31 (MPX1) Below 1 Ω
T4–18 (MPX2) – T5–16 (MPX2) Below 1 Ω

Result:
Result Proceed To
Both are OK A
MPX2 MPX1 One is OK B
Both are NG C
T5
Transponder Key ECU Assy

cardiagn.com
MPX2

S11
Smart ECU

B REPLACE TRANSMISSION CONTROL ECU

AND REPAIR OR REPLACE HARNESS AND
CONNECTOR

C REPAIR OR REPLACE HARNESS AND

MPX1 CONNECTOR
B79857

REPLACE TRANSMISSION CONTROL ECU

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2748

 05–2585
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM 05J68–01

DTC B1262 A/C ECU COMMUNICATION STOP

CIRCUIT DESCRIPTION
This DTC is detected when communication between the A/C control assy (A/C ECU) and gateway ECU stops
for more than 10 seconds.
DTC No. DTC Detection Condition Trouble Area

A/C control assy

B1262 A/C ECU communication
i ti stops
t

Wire harness

WIRING DIAGRAM
G1 A8
Gateway ECU Center Connector No. 2 A/C Control Assy

Instrument 4 13
GR B
Panel J/B Assy MPD2 5C 5J MPX+
12 3

cardiagn.com
Body ECU

9 8 8
GR GR
MPX1 1G 5K 5J MPX2+
17 11

J19
J/C 10 3
Y Y Y
5K 5J +B
D D 6

5 1K

Instrument GND
ECU–B 1
Panel J/B Assy

Engine Room J/B

1 1B
1 1
W DC/DC
3D 3M
2 1 W–B
F15
FL Block Assy B
MAIN 1
B
BE1
1

Battery
IJ

B79858

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2749

05–2586
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM

INSPECTION PROCEDURE
1 CHECK OPERATION

(a) Check that the A/C switch can operate the air conditioner normally.
OK: A/C switch can operate the air conditioner normally.
NG Go to step 2

OK

REPLACE A/C CONTROL ASSY

2 CHECK WIRE HARNESS (A/C CONTROL ASSY – BODY GROUND)

Wire Harness Side (a) Disconnect the A8 ECU connector.

A8 (b) Measure the resistance and voltage of the wire harness
A/C Control Assy (A/C ECU) side connector.

cardiagn.com
Standard:
Tester Connection Condition Specified Condition
A8–6 (+B) – Body ground Constant 10 to 14 V
A8–1 (GND) –
Constant Below 1 Ω
+B Body ground
GND
B79990 NG REPAIR OR REPLACE HARNESS AND
CONNECTOR

OK

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2750

 05–2587
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM

3 CHECK RESISTANCE OF COMMUNICATION LINE

(a) Disconnect the A8 and G1 ECU connectors.

Wire Harness Side
(b) Disconnect the 1G J/B connector.
A8 (c) Measure the resistance of the wire harness side connec-
A/C Control Assy (A/C ECU) tors.
Standard:
Tester Connection Specified Condition
A8–3 (MPX+) – G1–12 (MPD2) Below 1 Ω
A8–11 (MPX2+) – 1G–9 (MPX1) Below 1 Ω

Result:
Result Proceed to
MPX+ MPX2+ Both are OK A
One is OK B
G1
Both are NG C
Gateway ECU

cardiagn.com
MPD2

1G
Instrument Panel J/B Assy

B REPLACE A/C CONTROL ASSY AND REPAIR

OR REPLACE HARNESS AND CONNECTOR

MPX1
B79860 C REPAIR OR REPLACE HARNESS AND
CONNECTOR

REPLACE A/C CONTROL ASSY

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2751

05–2588
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM 05J6B–01

DTC B1271 COMBINATION METER ECU

COMMUNICATION STOP

CIRCUIT DESCRIPTION
This DTC is detected when communication between the combination meter assy (meter ECU) and gateway
ECU stops for more than 10 seconds.
DTC No. DTC Detection Condition Trouble Area

Combination meter assy

B1271 C bi ti meter
Combination t ECU communication
i ti stops
t

Wire harness

cardiagn.com

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2752

 05–2589
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM

WIRING DIAGRAM
P6
Power Source C10
Control ECU Center Connector No. 2 Combination Meter

13 13 3
GR P GR
MPX1 5G 5C IG2 MPX–
7 25

S11
Smart ECU Center Connector No. 1
16 2 2
B*1 W B
MPX2 4L 4C IG1 MPX+
32 24

W*2
T4

cardiagn.com
Transmission Control ECU Center Connector No. 1
8 7 7
GR GR
MPX1 II1 4I 4L
19

Instrument Panel J/B Assy Center Connector No. 2

13 8 16 11 9
R P L Y
1A 1L 5H 5D IG2
B 21
J6
J/C
B R

Center Connector No. 1

2 Engine Room J/B and
DOME
Engine Room R/B 15 4 4
1 G BR
4H 4C IG1
14
1 3M
BR

II
From Battery
*1: w/ Smart Entry System
*2: w/o Smart Entry System
B79522

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2753

05–2590
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM

INSPECTION PROCEDURE
1 CHECK OPERATION

(a) Check that the indicator (READY) on the combination meter illuminates when the hybrid vehicle control
system is operating (power switch ON (READY)).
OK: Indicator can operate properly.
NG Go to step 2

OK

REPLACE COMBINATION METER ASSY

2 CHECK WIRE HARNESS (COMBINATION METER ASSY – BODY GROUND)

Wire Harness Side (a) Disconnect the IG1 and IG2 meter connectors.
(b) Measure the resistance and voltage of the wire harness
IG1

cardiagn.com
(C10 Combination Meter) side connector.
Standard:
Tester Connection Specified Condition
IG2–9 – Body ground 10 to 14 V
IG1–4 – Body ground Below 1 Ω

IG2
(C10 Combination Meter)

B80254 B80259

NG REPAIR OR REPLACE HARNESS AND

CONNECTOR

OK

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2754

 05–2591
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM

3 CHECK RESISTANCE OF COMMUNICATION LINE

IG1 S11
(C10 Combination Meter) Smart ECU

T4
Transmission Control ECU

MPX+ MPX2*1

IG2
(C10 Combination Meter) P6
Power Source Control ECU

MPX1*2

cardiagn.com
B80260
MPX–
B80254 MPX1
B79862 B80262

(a) Disconnect the IG1 and IG2 meter connectors.

(b) Disconnect the P6 and, S11 or T4 ECU connectors.
(c) Measure the resistance of the wire harness side connectors.
Standard:
Tester Connection Specified Condition
IG1–2 (MPX+) – S11–32 (MPX2)*1 Below 1 Ω
IG1–2 (MPX+) – T4–19 (MPX1)*2 Below 1 Ω
IG2–3 (MPX–) – P6–7 (MPX1) Below 1 Ω

*1: w/ Smart entry system

*2: w/o Smart entry system
Result:
Result Proceed To
Both are OK A
One is OK B
Both are NG C

B REPLACE COMBINATION METER ASSY AND

REPAIR OR REPLACE HARNESS AND
CONNECTOR

C REPAIR OR REPLACE HARNESS AND

CONNECTOR

REPLACE COMBINATION METER ASSY

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2755

05–2592
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM 05J6E–01

DTC B1294 IMMOBILIZER ECU COMMUNICATION STOP

CIRCUIT DESCRIPTION
This DTC is detected when communication between the transponder key ECU (immobilizer ECU) and gate-
way ECU stops more than 10 seconds.
DTC No. DTC Detection Condition Trouble Area

Trans
Transponder
onder key ECU
B1294 T
Transponder
d kkey ECU communication
i ti stops
t

Wire harness

cardiagn.com

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2756

 05–2593
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM

WIRING DIAGRAM

T4 T5
Transmission Transponder
Control ECU Center Connector No. 1 Key ECU Assy
9 14 2
B B GR
MPX2 II1 4I 4D MPX2
18 16

B5
Body ECU Center Connector No. 1
11 11
B B
MPX2 4F 4D MPX1
15 17

cardiagn.com
Instrument Panel J/B Assy Center Connector No. 1
4 IGN 15 4 12
O O
To Battery 1J 1F 4G 4D IG
4

J25 Center Connector No. 1

J/C 5 13
W–B W–B W–B
4H 4D GND
A A 22

IH

B79523

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2757

05–2594
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM

INSPECTION PROCEDURE
1 INSPECT FUSE (IGN)

(a) Remove the IGN fuse from the instrument panel J/B
(b) Measure the resistance.
Standard: Below 1 Ω
NG REPLACE FUSE

OK

2 CHECK WIRE HARNESS (TRANSPONDER KEY ECU ASSY – BODY GROUND)

Wire Harness Side (a) Disconnect the T5 ECU connector.

T5 (b) Measure the voltage and resistance of the wire harness
Transponder Key ECU Assy side connectors.
Standard:

cardiagn.com
Tester Connection Condition Specified Condition
Power switch
T5–4 (IG) – Body ground
1: OFF → 2: ON (IG) 1: 0 V → 2: 10 to 14V
T5–22 (GND) –
Constant Below 1 Ω
IG GND Body ground
B79992

NG REPAIR OR REPLACE HARNESS AND

CONNECTOR

OK

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2758

 05–2595
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM

3 CHECK RESISTANCE OF COMMUNICATION LINE

Wire Harness Side (a) Disconnect the T4, T5 and B5 ECU connectors.
(b) Measure the resistance of the wire harness side connec-
tors.
T4
Standard:
Transmission Control ECU
Tester Connection Specified Condition
T5–17 (MPX1) – B5–15 (MPX2) Below 1 Ω
T5–16 (MPX2) – T4–18 (MPX2) Below 1 Ω

Result:
Result Proceed to
Both are OK A
MPX2 One is OK B
Both are NG C
T5
Transponder Key ECU Assy

cardiagn.com
MPX2 MPX1
B5
Body ECU

B REPLACE TRANSPONDER KEY ECU ASSY

AND REPAIR OR REPLACE HARNESS AND
CONNECTOR

MPX2 C REPAIR OR REPLACE HARNESS AND

CONNECTOR
B79864

REPLACE TRANSPONDER KEY ECU ASSY

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2759

05–2556
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM
05J5Q–01

DIAGNOSIS SYSTEM
1. DESCRIPTION
The gateway ECU controls the function of the multiplex communication system on the vehicle. Data of the
multiplex communication system and the Diagnostic Trouble Code (DTC) can be read in the Data Link Con-
nector 3 (DLC3) of the vehicle.
2. CHECK DLC3
DLC3 The vehicle’s ECU uses the ISO 15765–4 for communication
CG SG SIL protocol. The terminal arrangement of the DLC3 complies with
ISO 15031–03 and matches the ISO 15765–4 format.
1 2 3 4 5 6 7 8

9 10 11 12 1314 1516
BAT
A82779

Symbol Terminal No. Name Reference terminal Result Condition

SIL 7 Bus ”+” line 5 – Signal ground Pulse generation During transmission

cardiagn.com
CG 4 Chassis ground Body ground 1 Ω or less Always
SG 5 Signal ground Body ground 1 Ω or less Always
BAT 16 Battery positive Body ground 9 to 14 V Always

HINT:
Connect the cable of the hand–held tester (with CAN VIN) to the
DLC3, turn the power switch ON (IG) and attempt to use the tes-
ter. If the screen displays UNABLE TO CONNECT TO VE-
Hand–held HICLE, a problem exists in the vehicle side or the tester side.
Tester If communication is normal when the hand–held tester is con-
nected to another vehicle, inspect the DLC3 on the original ve-
CAN VIM
hicle.
DLC3 A82795 If communication is still impossible when the tester is connected
to another vehicle, the problem is probably in the tester itself.
Consult the Service Department listed in the tester’s instruction
manual.
3. INSPECT BATTERY VOLTAGE
Standard: 11 to 14 V
If voltage is below 11 V, recharge the battery before proceeding.

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2720

05–2558
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM
05J5S–01

DIAGNOSTIC TROUBLE CODE CHART

If a malfunction code is displayed during DTC check, check the circuit corresponding to the code in the table
below. Proceed to the page given for the circuit.
DTC No.
Detection Item Trouble Area
(See Page)

B1200
Wire harness

Body ECU communication stop
(05–2559)
Body ECU

B1207*
Wire harness

Smart ECU communication stop
(05–2563)
Smart ECU

B1210
Wire harness

Power source control ECU communication stop
(05–2567)
Power source control ECU

B1214,

Door system communication bus malfunction (+B short)
Wire harness
B1215

Door system communication bus malfunction (GND short)
ECUs (Door system bus)
(05–2571)
B1248
Wire harness
AVC–LAN communication impossible
(05–2579)
ECU (AVC–LAN system bus)

B1260
Wire harness

Transmission control ECU communication stop

cardiagn.com
(05–2581)
Transmission control ECU

B1262
Wire harness

A/C ECU communication stop
(05–2585)
A/C ECU

B1271
Wire harness

Combination meter ECU communication stop
(05–2588)
Meter ECU

B1294
Wire harness

Immobilizer ECU communication stop
(05–2592)
Transponder key ECU

*: w/ Smart entry system

HINT:
When ”+B or GND short malfunction of communication bus” DTCs (B1214, B1215, etc.) are detected at the
same time as ”communication stop” DTCs (B1211, B1212, etc.), please repair the ”+B or GND short malfunc-
tion of communication bus” DTCs first.

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2722

 05–2557
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM
05J5R–01

DTC CHECK/CLEAR

1. CHECK DTC
(a) Connect the hand–held tester (with CAN VIN) to the
DLC3 through the CAN VIN (controller area network ve-
hicle interface module).
Hand–held (b) Turn the power switch ON (IG).
Tester (c) Read DTCs by following the prompts on the hand–held
tester screen.
CAN VIM
HINT:
DLC3 A82795 Refer to the tester operator’s manual for further details.

2. CLEAR DTC
(a) Connect the hand–held tester (with CAN VIN) to the DLC3 through the CAN VIM.

cardiagn.com
(b) Turn the power switch ON (IG).
(c) Erase the DTCs by following the prompts on the tester screen.
HINT:
Refer to the hand–held tester operator’s manual for further details.

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2721

 05–2541
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM
05J6V–01

SYSTEM DESCRIPTION

The PRIUS primarily uses the 3 types of multiplex communication systems described below.

The Controller Area Network (CAN) is a network of the vehicle control systems (engine electrical,
chassis electrical, and hybrid system) and maintains communication between the ECUs.

The Body Electronics Area Network (BEAN) is a network of the ECUs of the body electric system
control and maintains communication between the ECUs.

The Audio Visual Communication–Local Area Network (AVC–LAN) is a network of the ECUs of
the audio visual system and the audio visual devices and maintains communication between the
devices and the ECUs.

These 3 types of multiplex communication systems are connected to the gateway ECU. The gateway
ECU, which is provided with communication circuits that support the 3 types of multiplex communica-
tion systems, enables communication among the multiplex communication systems that are con-
nected to the gateway ECU.
For example, to enable air conditioning control, the air conditioning ECU receives the engine coolant
temperature signal that is input into the ECM via the CAN, gateway ECU and BEAN.

cardiagn.com
: BEAN
: CAN
: AVC–LAN

Communication CAN⇔AVC–LAN

CAN Gateway ECU AVC–LAN

Communication Communication
CAN⇔BEAN AVC–LAN⇔BEAN

BEAN

B78780

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2705

05–2542
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM

The CAN in the PRIUS is established among the HV ECU, battery ECU, EPS ECU, ECM, skid control
ECU, steering angle sensor*, yaw rate & deceleration sensor*, gateway ECU and DLC3.
CAN System Diagram

: CAN

Battery ECU ECM

Steering Angle
Sensor*
Junction Junction
Yaw Rate &
Skid Control ECU Connector Connector
Deceleration Sensor*

cardiagn.com
No. 1 No. 2

EPS ECU

DLC3 Gateway ECU HV ECU

to/from to AVC–LAN
BEAN

* :w/ VSC System

B78781

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2706

 05–2543
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM

The BEAN in the PRIUS is established among the body ECU, meter ECU, A/C ECU, transponder key
ECU, power source control ECU, transmission control ECU, smart ECU* and gateway ECU.
BEAN System Diagram

: BEAN

Multiplex Network
Body ECU

Meter ECU A/C ECU

cardiagn.com
Transponder Key Power Source
ECU Control ECU

Transmission
Smart ECU*
Control ECU

to/from CAN
Gateway ECU
to/from AVC–LAN

DLC3

*: w/ Smart Entry System

B78929

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2707

05–2544
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM

The AVC–LAN is established among the multi – display, audio head unit, navigation ECU* and gate-
way ECU.
AVC–LAN System Diagram

: AVC–LAN

Navigation ECU*

multi – display

cardiagn.com
Audio Head Unit Gateway ECU

from CAN to/from

BEAN

*: Optional Equipment
B78930

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2708

 05–2545
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM

BASIC OF MPX (Multiplex Communication)

1. GENERAL
The PRIUS multiplex communication system uses serial communication, which converts multiple pieces of
information into serial communication data. As a result, they can be transmitted through a single communica-
tion wire.

Conceptual Drawing

Switch
Light
On On

Motor
Off
Battery ECU ECU
Heater

Solenoid

cardiagn.com
Serial Communication
B78765 B79348

Serial communication data consists of bits and frames. A bit is the basic unit that represents the
amount of information. A bit is represented by binary values ”0” or ”1”. A frame is a body of data that
is transmitted together. A frame contains a ”header” that indicates the beginning of the data and an
”end” message that indicates the end of the data.

Frame

Data

Header End Message

B78766

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2709

05–2546
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM

2. NETWORK STYLE
Based on serial communication, various ECUs are connected on a network to exchange various pieces of
information. Such a system is called a multiplex communication system.

The CAN communication on the PRIUS uses the multi star style bus connection. In this style of net-
work, the ECUs are connected in a star shape. The ECUs cannot establish communication with other
ECUs without passing through the master ECUs. For the Prius, the 2 junction connectors are the mas-
ter ECUs and they are connected with main bus lines. Each of the junction connectors extends sub
bus lines and communicates between all the connected ECUs.

Sub
Bus Line
ECU ECU

Main
Junction Bus Line Junction

cardiagn.com
Connector Connector
ECU ECU

B78770

The BEAN on the PRIUS uses the ring and bus styles of networks to connect ECUs. The connection
method is called a daisy chain. In a daisy chain, communication can be maintained even if there is an
area that has an open circuit. The ECUs are connected in a ring form, which enables a signal that is
output by a transmitting ECU to circle the ring and return to its original ECU. This ring also functions
as a single common communication wire. The transmitting ECUs output signals through a common
communication wire and the receiving ECUs input data through a common communication wire.

ECU ECU

Daisy
Chain

ECU ECU
Open

B78774 B79349

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2710

 05–2547
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM

The AVC–LAN in the PRIUS uses a star style. This style is centered on a master ECU, which holds
a central control function. The ECUs are connected in a star shape. The ECUs cannot establish com-
munication with other ECUs without passing through the master ECU. For the Prius, the multi display
or audio head unit functions as a master ECU.

ECU

ECU ECU

cardiagn.com
Multi–display

B78772

3. DIFFERENCE OF CAN, BEAN AND AVC–LAN

Data for respective protocols (CAN, BEAN and AVC–LAN) are arranged differently. Therefore, it is not pos-
sible to exchange data between different protocols. For this reason, data arrangement must be converted
before transferring data to communication bus (CAN, BEAN and AVC–LAN). This conversion is called gate-
way function, which is performed by the gateway ECU.
Chassis Electrical
Control Body Electrical System Control Body Electrical System Control
System Control
CAN BEAN AVC–LAN
Protocol
(ISO Standard) (TOYOTA Original) (TOYOTA Original)
500 k bps
Communication Speed Max. 10 k bps Max. 17.8 k bps
(Max. 1 M bps)
Communication Wire Twisted–pair Wire AV Single Wire Twisted–pair Wire
Drive Type Differential Voltage Drive Single Wire Voltage Drive Differential Voltage Drive
Data Length 1 – 8 Byte (Variable) 1 – 11 Byte (Variable) 0 – 32 Byte (variable)

*: ”bps” stands for bit per second.

Although BEAN and AVC–LAN communicate at almost the same speed, the CAN communication speed is
much faster than BEAN or AVC–LAN. When the vehicle control system uses BEAN or AVC–LAN, which have
a slower communication speed than CAN, it means that the system control could be delayed by the slow
speed. For this reason, the vehicle control system uses CAN, which can send and receive a large volume
of data at one time, in addition to being able to transmit at a faster speed.

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2711

05–2548
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM

4. COMMUNICATION WIRE
A single, automobile vinyl (AV) wire is used for BEAN communication. A twisted–pair wire is used for CAN
and AVC–LAN communication.

Function Outline

AV Single Wire
Lightweight single communication wire that consists of single core line
surrounded by insulation. Voltage is applied to this line in order to drive
communication. This system is called ”single wire voltage drive”.

Twisted–pair Wire for AVC–LAN Pair of lines is twisted together and covered with insulation. Commu-
nication is driven by applying positive (+) and negative (–) voltage to two
lines in order to send single signal. This system, which is called ”differ-
ential voltage drive”, can reduce noise.

Twisted–pair Wire for CAN Pair of lines is twisted. Communication is driven by applying 1.5 to 2.5
V and 2.5 to 3.5 V of voltage to two lines in order to send single signal.

cardiagn.com
This system, which is called ”differential voltage drive”, can reduce
Shield
noise.

B78777 B79350 B80336 B80263

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2712

05–2540
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM
05J5L–01

SYSTEM DIAGRAM

: BEAN

Multiplex Network
Body ECU

Meter ECU A/C ECU

cardiagn.com
Transponder Key Power Source
ECU Control ECU

Transmission
Smart ECU*
Control ECU

to/from CAN
Gateway ECU
to/from AVC–LAN

DLC3

*: w/ Smart Entry System

B78929

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2704

 05–2549
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM
05J5M–01

HOW TO PROCEED WITH TROUBLESHOOTING

HINT:

Use this procedure to troubleshoot the multiplex communication system.

The hand–held tester should be used in step 2.
1 VEHICLE BROUGHT TO WORKSHOP

2 DTC CHECK (See page 05–2557)

(a) Check for DTCs and note any codes that are output.
(b) Delete the DTC.
(c) Recheck for DTCs. Try to prompt the DTC by simulating the original activity that the DTC suggests.
(1) If the DTC does not reoccur, proceed to A.
(2) If the DTC reoccurs, proceed to B.
B Go to step 4

cardiagn.com
A

3 OVERALL ANALYSIS AND TROUBLESHOOTING

(a) Terminals of ECU (see page 05–2550)

4 ADJUST, REPAIR OR REPLACE

5 CONFIRMATION TEST

END

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2713

05–2538
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM
05J5J–01

LOCATION
BEAN Component

Combination Meter (Meter ECU)

Smart ECU* Gateway ECU

Power Source Control ECU

cardiagn.com
Transponder Key ECU Assy

Transmission Control ECU

A/C Control Assy (A/C ECU)

DLC3
Instrument Panel J/B Assy

Multiplex Network Body ECU

*: w/ Smart Entry System

B80264

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2702

 05–2539
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM

AVC–LAN Component

Multi–display Gateway ECU

Audio Head Unit

cardiagn.com
Navigation ECU*

*: Optional Equipment

B80265

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2703

 05–2537
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM

MULTIPLEX COMMUNICATION SYSTEM

05J6T–01

PRECAUTION
NOTICE FOR INITIALIZATION:
When disconnecting the negative (–) battery terminal, initialize the following system(s) after the ter-
minal is reconnected.
System Name See Page
Power Window Control System 05–2028

NOTICES FOR HYBRID SYSTEM ACTIVATION:

When the warning lamp is illuminated or the battery has been disconnected and reconnected, press-
ing the power switch may not start the system on the first try. If so, press the power switch again.

cardiagn.com

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2701

05–2550
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM
05J5P–01

TERMINALS OF ECU
1. CHECK GATEWAY ECU

G1

B75719

(a) Disconnect the G1 ECU connector.

(b) Measure the voltage and resistance between each terminal of the wire harness side connector and
body ground.
Standard:
Symbols
Wiring Color Terminal Description Condition Specified Condition

cardiagn.com
(Terminal No.)
BATT (G1–10) –
Y – Body ground +B (BATT) power supply Constant 10 to 14 V
Body ground
IG (G1–1) –
B – Body ground Ignition power supply Ignition switch ON 10 to 14 V
Body ground
ACC (G1–2) –
P – Body ground ACC power supply Ignition switch ACC 10 to 14 V
Body ground
SIL (G1–7) –
W – Body ground Bus ”+” line During transmission Pulse generation
Body ground
MPD2 (G1–12) – GR –
MPX line Constant 10 kΩ or higher
Body ground Body ground
MPD1 (G1–3) – GR –
MPX line Constant 10 kΩ or higher
Body ground Body ground
GTX+ (G1–6) –
B – Body ground AVC–LAN line Constant 10 kΩ or higher
Body ground
GTX– (G1–21) –
W – Body ground AVC–LAN line Constant 10 kΩ or higher
Body ground
GND (G1–24) – W–B –
Ground Constant Below 1 Ω
Body ground Body ground

If the result is not as specified, there may be a malfunction on the wire harness side.

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2714

 05–2551
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM

2. CHECK A/C ECU

A8

B75722 B79225

(a) Disconnect the A8 ECU connector.

(b) Measure the voltage and resistance between each terminal of the wire harness side connector and
body ground.
Standard:
Symbols
Wiring Color Terminal Description Condition Specified Condition
(Terminal No.)

cardiagn.com
+B (A8–6) –
Y – Body ground +B power supply Constant 10 to 14 V
Body ground
MPX+ (A8–3) –
B – Body ground MPX line Constant 10 kΩ or higher
Body ground
MPX2+ (A8–11) – GR –
MPX line Constant 10 kΩ or higher
Body ground Body ground
GND (A8–1) – W–B –
Ground Constant Below 1 Ω
Body ground Body ground

If the result is not as specified, there may be a malfunction on the wire harness side.

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2715

05–2552
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM

3. CHECK INSTRUMENT PANEL J/B ASSY (MULTIPLEX NETWORK BODY ECU)

Vehicle Rear Side Vehicle Front Side

1G
B5

1A
1E

cardiagn.com
Multiplex Network
Body ECU
1A 1E

1G

B5

B70491
B79229 B80270

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2716

 05–2553
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM

(a) Disconnect the B5 ECU connector.

(b) Disconnect the 1A, 1E and 1G J/B connectors.
(c) Measure the voltage and resistance of each terminal of the wire harness side connectors.
Standard:
Symbols
Wiring Color Terminal Description Condition Specified Condition
(Terminal No.)
ECUB (1A–30) –
R – Body ground +B (ECUB) power supply Constant 10 to 14 V
Body ground
MPX1 (1G–9) – GR –
MPX line Constant 10 kΩ or higher
Body ground Body ground
MPX2 (B5–15) –
B – Body ground MPX line Constant 10 kΩ or higher
Body ground
GND (1E–17) – W–B –
Ground Constant Below 1 Ω
Body ground Body ground

If the result is not as specified, there may be a malfunction on the wire harness side.
4. CHECK TRANSPONDER KEY ECU

T5

cardiagn.com
B75719

(a) Disconnect the T5 ECU connector.

(b) Measure the voltage and resistance of each terminal of the wire harness side connector.
Standard:
Symbols
Wiring Color Terminal Description Condition Specified Condition
(Terminal No.)
IG (T5–4) –
O – Body ground +B (IG) power supply Constant 10 to 14 V
Body ground
MPX1 (T5–17) –
B – Body ground MPX line Constant 10 kΩ or higher
Body ground
MPX2 (T5–16) – GR –
MPX line Constant 10 kΩ or higher
Body ground Body ground
GND (T5–22) – W–B –
Ground Constant Below 1 Ω
Body ground Body ground

If the result is not as specified, there may be a malfunction on the wire harness side.

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2717

05–2554
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM

5. CHECK TRANSMISSION CONTROL ECU

T4

B75720

(a) Disconnect the T4 ECU connector.

(b) Measure the voltage and resistance of each terminal of the wire harness side connector.
Standard:
Symbols
Wiring Color Terminal Description Condition Specified Condition
(Terminal No.)
+B (T4–1) –
L – Body ground +B power supply Constant 10 to 14 V

cardiagn.com
Body ground
MPX1 (T4–19) – GR –
MPX line Constant 10 kΩ or higher
Body ground Body ground
MPX2 (T4–18) –
B – Body ground MPX line Constant 10 kΩ or higher
Body ground
E1 (T4–15) – W–B –
Ground Constant Below 1 Ω
Body ground Body ground

If the result is not as specified, there may be a malfunction on the wire harness side.

6. CHECK SMART ECU

S11

B75721

(a) Disconnect the S11 ECU connector.

(b) Measure the voltage and resistance of each terminal of the wire harness side connector.
Standard:
Symbols
Wiring Color Terminal Description Condition Specified Condition
(Terminal No.)
+B (S11–1) –
O – Body ground +B power supply Constant 10 to 14 V
Body ground
MPX1 (S11–31) – GR –
MPX line Constant 10 kΩ or higher
Body ground Body ground
MPX2 (S11–32) –
B – Body ground MPX line Constant 10 kΩ or higher
Body ground
E (S11–17) – W–B –
Ground Constant Below 1 Ω
Body ground Body ground

If the result is not as specified, there may be a malfunction on the wire harness side.

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2718

 05–2555
DIAGNOSTICS – MULTIPLEX COMMUNICATION SYSTEM

7. CHECK METER ECU (COMBINATION METER)

C10

B75723

(a) Disconnect the C10 ECU connector.

(b) Measure the voltage and resistance each terminal of the wire harness side connector.
Standard:
Symbols
Wiring Color Terminal Description Condition Specified Condition
(Terminal No.)
– (C10–21) –
Y – Body ground +B power supply Constant 10 to 14 V

cardiagn.com
Body ground
MPX+ (C10–24) –
B – Body ground MPX line Constant 10 kΩ or higher
Body ground
MPX– (C10–25) – GR –
MPX line Constant 10 kΩ or higher
Body ground Body ground
– (C10–14) – BR –
Ground Constant Below 1 Ω
Body ground Body ground

If the result is not as specified, there may be a malfunction on the wire harness side.

8. CHECK POWER SOURCE CONTROL ECU

P6

B75721

(a) Disconnect the P6 ECU connector.

(b) Measure the voltage and resistance of each terminal of the wire harness side connector.
Standard:
Symbols
Wiring Color Terminal Description Condition Specified Condition
(Terminal No.)
AM1 (P6–33) –
R – Body ground +B (AM1) power supply Constant 10 to 14 V
Body ground
MPX1 (P6–7) – GR –
MPX line Constant 10 kΩ or higher
Body ground Body ground
MPX2 (P6–24) –
B – Body ground MPX line Constant 10 kΩ or higher
Body ground
GND2 (P6–6) – W–B –
Ground Constant Below 1 Ω
Body ground Body ground

If the result is not as specified, there may be a malfunction on the wire harness side.

2004 Prius – Preliminary Release (RM1075U)

Author: Date: 2719