NETWORKING: CAN COMMUNICATION SYSTEM: U0104; Lost Communication with Driving Support ECU; 2016 - 2017 MY Sienna [12/2015

Last Modified: 04-05-2023	6.11:8.1.0	Doc ID: RM100000000VJE8
Model Year Start: 2016	Model: Sienna	Prod Date Range: [12/2015 - 11/2017]
Title: NETWORKING: CAN COMMUNICATION SYSTEM: U0104; Lost Communication with Driving Support ECU; 2016 - 2017 MY Sienna [12/2015 - 11/2017]

DTC

U0104

Lost Communication with Driving Support ECU

DESCRIPTION

DTC Code	DTC Detection Condition	Trouble Area
U0104	No communication from the driving support ECU.	Driving support ECU assembly branch wire or connector Power source circuit of driving support ECU assembly Driving support ECU assembly

HINT:

For vehicle with dynamic radar cruise control system only.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

Turn the ignition switch off before measuring the resistances between CAN bus main wires and between CAN bus branch wires.
Turn the ignition switch off before inspecting CAN bus wires for a ground short.
After the ignition switch is turned off, check that the key reminder warning system and light reminder warning system are not operating.
Before measuring the resistance, leave the vehicle as is for at least 1 minute and do not operate the ignition switch, any other switches or the doors. If any doors need to be opened in order to check connectors, open the doors and leave them open.
Inspect the fuses for circuits related to this system before performing the following inspection procedure.

HINT:

Operating the ignition switch, any other switches or a door triggers related ECU and sensor communication on the CAN. This communication will cause the resistance value to change.
Even after DTCs are cleared, if a DTC is stored again after driving the vehicle for a while, the malfunction may be occurring due to vibration of the vehicle. In such a case, wiggling the ECUs or wire harness while performing the inspection below may help determine the cause of the malfunction.

PROCEDURE

1.	PRECAUTION

NOTICE:

After turning the ignition switch off, waiting time may be required before disconnecting the cable from the battery terminal. Therefore, make sure to read the disconnecting the cable from the battery terminal notice before proceeding with work (See page ).

2.	DISCONNECT CABLE FROM NEGATIVE BATTERY TERMINAL

(a) Disconnect the cable from the negative (-) battery terminal before measuring the resistances of the main wire and the branch wire.

CAUTION:

Wait at least 90 seconds after disconnecting the cable from the negative (-) battery terminal to prevent airbag and seat belt pretensioner activation.

NOTICE:

When disconnecting the cable, some systems need to be initialized after the cable is reconnected (See page ).

3.	CHECK FOR OPEN IN CAN BUS WIRE (DRIVING SUPPORT ECU ASSEMBLY BRANCH WIRE)

(a) Disconnect the driving support ECU assembly connector.

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

Standard Resistance:

Tester Connection	Switch Condition	Specified Condition
A44-39 (CA2H) - A44-17 (CA2L)	Ignition switch off	54 to 69 Ω

Text in Illustration

*a	Rear view of wire harness connector (to Driving Support ECU Assembly)

REPAIR OR REPLACE CAN BRANCH WIRE OR CONNECTOR (CAN-H, CAN-L)

4.	CHECK HARNESS AND CONNECTOR (DRIVING SUPPORT ECU ASSEMBLY - POWER SOURCE)

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

NOTICE:

When disconnecting the cable, some systems need to be initialized after the cable is reconnected (See page ).

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

Standard Voltage:

Tester Connection	Switch Condition	Specified Condition
A44-30 (B) - Body ground	Ignition switch ON	11 to 14 V

Standard Resistance:

Tester Connection	Condition	Specified Condition
A44-25 (GND) - Body ground	Always	Below 1 Ω

Text in Illustration

*a	Rear view of wire harness connector (to Driving Support ECU Assembly)

REPLACE DRIVING SUPPORT ECU ASSEMBLY

REPAIR OR REPLACE HARNESS OR CONNECTOR