Main Body ECU Communication Stop Mode [09/2022 - 11/2022]: Procedure

WARNING: This page is about a different car, the 2023 Toyota GR Corolla and 2023 Toyota Corolla. However, it is still accessible from the selected car via links, so may be relevant.

CHECK FOR OPEN IN CAN BUS LINES (MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU) BRANCH LINE)

Disconnect the cable from the negative (-) battery terminal.
Disconnect the I85 main body ECU (multiplex network body ECU) connector.

Measure the resistance according to the value(s) in the table below.

Standard Resistance

Tester Connection	Condition	Specified Condition
I85-5 (CANH) - I85-4 (CANL)	Cable disconnected from negative (-) battery terminal	54 to 69 Ω

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

*a	Front view of wire harness connector (to Main Body ECU (Multiplex Network Body ECU))

Result

Result
OK
NG

Result:

REPAIR OR REPLACE CAN BRANCH LINES OR CONNECTOR (MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU))

Result:

See step 2

CHECK HARNESS AND CONNECTOR (POWER SOURCE CIRCUIT)

Remove the main body ECU (multiplex network body ECU).
Refer to REMOVAL [09/2022 - 11/2022]

Measure the resistance according to the value(s) in the table below.

Standard Resistance

Tester Connection	Condition	Specified Condition
MB-11 (GND1) - Body ground	Cable disconnected from negative (-) battery terminal	Below 1 Ω

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

*a	Front view of wire harness connector (to Main Body ECU (Multiplex Network Body ECU))

NOTE:

Perform this inspection with the wire harness connected to the instrument panel junction block assembly.

Reconnect the cable to the negative (-) battery terminal.

Measure the voltage according to the value(s) in the table below.

Standard Voltage

Tester Connection	Condition	Specified Condition
MB-31 (BECU) - Body ground	Always	11 to 14 V
MB-30 (ACC) - Body ground	Ignition switch ACC	11 to 14 V
MB-32 (IG) - Body ground	Ignition switch ON	11 to 14 V

NOTE:

Perform this inspection with the wire harness connected to the instrument panel junction block assembly.

Result

Result	Proceed to
OK	A
NG (BECU)	B
NG (ACC)	C
NG (IG)	D
NG (GND1)	E

Result:

REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU)

Refer to REMOVAL [09/2022 - 11/2022]

Result:

GO TO LIGHTING (INT) SYSTEM (ACC SIGNAL CIRCUIT)

Refer to ACC Signal Circuit [09/2022 - 11/2022]

Result:

GO TO LIGHTING (INT) SYSTEM (IG SIGNAL CIRCUIT)

Refer to IG Signal Circuit [09/2022 - 11/2022]

Result:

See step 4

Result:

See step 3

CHECK HARNESS AND CONNECTOR (BECU SIGNAL CIRCUIT)

Disconnect the cable from the negative (-) battery terminal.
Disconnect the 4B instrument panel junction block assembly connector.
Reconnect the cable to the negative (-) battery terminal.

Measure the voltage according to the value(s) in the table below.

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

*a	Front view of wire harness connector (to Instrument Panel Junction Block Assembly)

Standard Voltage

Tester Connection	Condition	Specified Condition
4B-1 - Body ground	Always	11 to 14 V

Result

Result
OK
NG

Result:

REPLACE INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY

Refer to REMOVAL [09/2022 - 11/2022]

Result:

REPAIR OR REPLACE HARNESS OR CONNECTOR (BECU SIGNAL CIRCUIT)

CHECK HARNESS AND CONNECTOR (GROUND CIRCUIT)

Disconnect the cable from the negative (-) battery terminal.
Disconnect the 4F instrument panel junction block assembly connector.

Measure the resistance according to the value(s) in the table below.

*a	Front view of wire harness connector (to Instrument Panel Junction Block Assembly)

Standard Resistance

Tester Connection	Condition	Specified Condition
4F-3 - Body ground	Cable disconnected from negative (-) battery terminal	Below 1 Ω

Result

Result
OK
NG

Result:

REPLACE INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY

Refer to REMOVAL [09/2022 - 11/2022]

Result:

REPAIR OR REPLACE HARNESS OR CONNECTOR (GROUND CIRCUIT)