Toyota CH-R Service Manual: Certification ECU Communication Stop Mode

DESCRIPTION

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

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

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.
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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 or any 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.
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After performing repairs, perform the DTC check procedure and confirm that the DTCs are not output again.
DTC check procedure: Turn the ignition switch to ON and wait 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.
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Inspect the fuses for circuits related to this system before performing the following procedure.
Before replacing the certification ECU (smart key ECU assembly), refer to Registration.
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HINT:

Before disconnecting related connectors for inspection, push in on each connector body to check that the connector is not loose or disconnected.
When a connector is disconnected, check that the terminals and connector body are not cracked, deformed or corroded.

PROCEDURE

1.	CHECK FOR OPEN IN CAN BUS LINES (CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) BRANCH LINE)

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

(b) Disconnect the certification ECU (smart key ECU assembly) connector.

Standard Resistance:

Tester Connection	Condition	Specified Condition
F1-1 (CANH) - F1-2 (CANL)	Cable disconnected from negative (-) battery terminal	54 to 69 Ω

*a	Front view of wire harness connector (to Certification ECU (Smart Key ECU Assembly))

REPAIR OR REPLACE CAN BRANCH LINES OR CONNECTOR (CERTIFICATION ECU (SMART KEY ECU ASSEMBLY))

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
F1-18 (E) - Body ground	Cable disconnected from negative (-) battery terminal	Below 1 Ω

*a	Front view of wire harness connector (to Certification ECU (Smart Key ECU Assembly))

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

Standard Voltage:

Tester Connection	Condition	Specified Condition
F1-4 (+B) - Body ground	Always	11 to 14 V
F1-15 (CUTB) - Body ground	Always	11 to 14 V

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

REPAIR OR REPLACE HARNESS OR CONNECTOR (POWER SOURCE CIRCUIT)

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Toyota C-HR (AX20) 2023-2026 Owner's Manual