Toyota Avalon (XX50) 2019-2022 Service & Repair Manual: ECM Communication Stop Mode

DESCRIPTION

Detection Item

Symptom

Trouble Area

ECM Communication Stop Mode

Any of the following conditions are met:

Communication stop for "ECM (Engine)" is indicated on the "Communication Bus Check" screen of the Techstream.
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Communication stop history for "ECM (Engine)" is indicated on the "Communication Bus Check (Detail)" screen of the Techstream. (The Lost Communication Time value for "ECM (Engine)" is 6 or more.)
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Communication system DTCs (DTCs that start with U) that correspond to "ECM Communication Stop Mode" in "DTC Combination Table" are output.
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WIRING DIAGRAM

CAUTION / NOTICE / HINT

CAUTION:

When performing the confirmation driving pattern, obey all speed limits and traffic laws.

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 power 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 (-) auxiliary battery terminal and leave the vehicle for 1 minute or more before measuring the resistance.
After turning the power switch off, waiting time may be required before disconnecting the cable from the negative (-) auxiliary battery terminal. Therefore, make sure to read the disconnecting the cable from the negative (-) auxiliary 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 power switch on (IG) and wait for 1 minute or more. Then operate the suspected malfunctioning system and drive the vehicle at 60 km/h (37 mph) or more for 5 minutes or more.
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.

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 (ECM MAIN LINE AND BRANCH LINE)

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

(b) Disconnect the A19 ECM connector.

Standard Resistance:

Bus 2 Main Lines

Tester Connection	Condition	Specified Condition
A19-8 (CANH) - A19-18 (CANL)	Cable disconnected from negative (-) auxiliary battery terminal	108 to 132 Ω

Bus 4 Branch Lines

Tester Connection	Condition	Specified Condition
A19-7 (CAN+) - A19-17 (CAN-)	Cable disconnected from negative (-) auxiliary battery terminal	54 to 69 Ω

*a	Front view of wire harness connector (to ECM)

REPAIR OR REPLACE CAN MAIN BUS LINES OR CONNECTOR (ECM)

REPAIR OR REPLACE CAN BRANCH LINES OR CONNECTOR (ECM)

2.	CHECK ECM POWER SOURCE CIRCUIT

(a) Check the ECM power source circuit.

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REPLACE ECM

REPAIR OR REPLACE HARNESS OR CONNECTOR (POWER SOURCE CIRCUIT)

Toyota Avalon (XX50) 2019-2022 Service & Repair Manual > Can Communication System(for Gasoline Model): Check Bus 3 Line for Short to GND
DESCRIPTION There may be a short circuit between one of the CAN bus lines and GND when there is no resistance between terminal 6 (CA3H) of the central gateway ECU (network gateway ECU) and terminal 4 (CG) of the DLC3, or terminal 21 (CA3L) of the central gateway ECU (network gateway ECU) and termina ...

Toyota Avalon (XX50) 2019-2022 Owners Manual