DTC U1100: Lost Communication with Seat Belt Control ECU [08/2013 - ]: Procedure

WARNING: This page is about a different car, the 2014 Lexus ES 300h. However, it is still accessible from the selected car via links, so may be relevant.

RECONFIRM DTC OUTPUT

Reconfirm DTCs.

HINT:

If DTC U1002 is output from PM1 Gateway of the power management control ECU, this indicates a sub bus 11 malfunction. Troubleshoot for DTC U1002 and check for malfunctions in sub bus 11.

Result

Result	Proceed to
U1002 is not output from power management control ECU (Techstream display: PM1 Gateway)	A
U1002 is output from power management control ECU (Techstream display: PM1 Gateway)	B

B → See step 5

A: Go to next step

CHECK CAN BUS LINE FOR DISCONNECTION (SEAT BELT CONTROL ECU BRANCH LINE)

Disconnect the cable from the negative (-) auxiliary battery terminal.

Disconnect the H78 seat belt control ECU connector.

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

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

Standard Resistance

Tester Connection	Condition	Specified Condition
H78-1 (CANH) - H78-2 (CANL)	Cable disconnected from negative (-) auxiliary battery terminal	54 to 69 Ω

TEXT IN ILLUSTRATION

*a	Front view of wire harness connector (to Seat Belt Control ECU)

NG → REPAIR OR REPLACE CAN BRANCH LINE OR CONNECTOR (SEAT BELT CONTROL ECU)

OK: Go to next step

CHECK HARNESS AND CONNECTOR (POWER SOURCE TERMINAL)

Disconnect the H77 seat belt control ECU connector.

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

Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

Standard Resistance

Tester Connection	Condition	Specified Condition
H77-8 (PGND) - Body ground	Cable disconnected from negative (-) auxiliary battery terminal	Below 1 Ω

TEXT IN ILLUSTRATION

*a	Front view of wire harness connector (to Seat Belt Control ECU)

Connect the cable to the negative (-) auxiliary battery terminal.

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

Standard Voltage

Tester Connection	Condition	Specified Condition
H77-7 (+B) - Body ground	Power switch off	11 to 14 V
H78-8 (IG1) - Body ground	Power switch on (IG)	11 to 14 V

TEXT IN ILLUSTRATION

*a	Front view of wire harness connector (to Seat Belt Control ECU)

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR (POWER SOURCE CIRCUIT)

OK → See step 4

REPLACE SEAT BELT CONTROL ECU. Refer to REMOVAL [08/2013 - ]
GO TO DIAGNOSIS PROCEDURE INDICATED BY OUTPUT DTC. Refer to DTC U1002: Lost Communication with Gateway Module [08/2013 - ]