Toyota CH-R Service Manual: DCM Communication Stop Mode

DESCRIPTION

Detection Item	Symptom	Trouble Area
DCM Communication Stop Mode	Any of the following conditions are met: Communication stop for "DCM" is indicated on the "Communication Bus Check" screen of the Techstream. Click here Communication stop history for "DCM" is indicated on the "Communication Bus Check (Detail)" screen of the Techstream. (The Lost Communication Time value for "DCM" is 6 or more.) Click here Communication system DTCs (DTCs that start with U) that correspond to "DCM Communication Stop Mode" in "DTC Combination Table" are output. Click here	Telematics transceiver branch line or connector Power source circuit of telematics transceiver Telematics transceiver ground circuit Telematics transceiver

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

Before measuring the resistance of the CAN bus, turn the ignition switch off and leave the vehicle for 1 minute or more without operating the key, switches or opening or closing the doors. After that, disconnect the cable from the negative (-) battery terminal and leave the vehicle for 1 minute or more before measuring the resistance.
After turning the ignition switch off, waiting time may be required before disconnecting the cable from the negative (-) battery terminal. Therefore, make sure to read the disconnecting the cable from the negative (-) battery terminal notices before proceeding with work.
Click here
Because the order of diagnosis is important to allow correct diagnosis, make sure to begin troubleshooting using How to Proceed with Troubleshooting when CAN communication system related DTCs are output.
Click here
After performing repairs, perform the DTC check procedure and confirm that the DTCs are not output again.
DTC check procedure: Turn the ignition switch ON and wait for at least approximately 20 seconds.
After the repair, perform the CAN bus check and check that all the ECUs and sensors connected to the CAN communication system are displayed as normal.
Click here
Inspect the fuses for circuits related to this system before performing the following 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.	CHECK FOR OPEN IN CAN BUS LINES (TELEMATICS TRANSCEIVER BRANCH LINE)

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

(b) Disconnect the telematics transceiver connector.

Standard Resistance:

Tester Connection	Condition	Specified Condition
F134-15 (CANP) - F134-16 (CANN)	Cable disconnected from negative (-) battery terminal	54 to 69 Ω

*a	Front view of wire harness connector (to Telematics Transceiver)

REPAIR OR REPLACE CAN BRANCH LINES OR CONNECTOR (TELEMATICS TRANSCEIVER)

2.	CHECK HARNESS AND CONNECTOR (POWER SOURCE CIRCUIT)

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
F134-4 (E) - Body ground	Cable disconnected from negative (-) battery terminal	Below 1 Ω

*a	Front view of wire harness connector (to Telematics Transceiver)

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

Standard Voltage:

REPLACE TELEMATICS TRANSCEIVER

REPAIR OR REPLACE HARNESS OR CONNECTOR (POWER SOURCE CIRCUIT)

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Toyota C-HR (AX20) 2023-2025 Owner's Manual