Toyota Avalon (XX50): Check Bus 2 Lines for Short Circuit

Toyota Avalon (XX50) 2019-2022 Service & Repair Manual / Power Source, Network / Networking / Can Communication System(for Hv Model) / Check Bus 2 Lines for Short Circuit

DESCRIPTION

There may be a short circuit between the CAN main bus lines and/or CAN branch lines when the resistance between terminals 18 (CA4H) and 17 (CA4L) of the central gateway ECU (network gateway ECU) is below 54 Ω.

Symptom	Trouble Area
Resistance between terminals 18 (CA4H) and 17 (CA4L) of the central gateway ECU (network gateway ECU) is below 54 Ω.	Short in CAN main bus lines Short in CAN branch lines Central gateway ECU (network gateway ECU) ECM Hybrid vehicle control ECU Brake booster with master cylinder assembly Inverter with converter assembly No. 2 CAN junction connector No. 4 CAN junction connector

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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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 SHORT IN CAN BUS LINES (NO. 2 CAN JUNCTION CONNECTOR)

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

(b) Disconnect the A49 No. 2 CAN junction connector.

Front view of wire harness connector

(to No. 2 CAN Junction Connector)

to Inverter with Converter Assembly

to Brake Booster with Master Cylinder Assembly

to No. 4 CAN Junction Connector

to ECM

Standard Resistance:

Tester Connection	Condition	Specified Condition	Connected to
A49-8 (CANH) - A49-19 (CANL)	Cable disconnected from negative (-) auxiliary battery terminal	200 Ω or higher	Inverter with converter assembly
A49-9 (CANH) - A49-20 (CANL)	Cable disconnected from negative (-) auxiliary battery terminal	200 Ω or higher	Brake booster with master cylinder assembly
A49-10 (CANH) - A49-21 (CANL)	Cable disconnected from negative (-) auxiliary battery terminal	108 to 132 Ω	No. 4 CAN junction connector
A49-11 (CANH) - A49-22 (CANL)	Cable disconnected from negative (-) auxiliary battery terminal	108 to 132 Ω	ECM

Result	Proceed to
OK	A
NG (Line to ECM)	B
NG (Line to No. 4 CAN junction connector)	C
NG (Line to ECU or sensor)	D

REPLACE NO. 2 CAN JUNCTION CONNECTOR

GO TO STEP 3

GO TO STEP 6

2.	CHECK FOR SHORT IN CAN BUS LINES (NO. 2 CAN JUNCTION CONNECTOR - ECM)

(a) Disconnect the A19 ECM connector.

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

Front view of wire harness connector

(to No. 2 CAN Junction Connector)

to ECM

Standard Resistance:

Tester Connection	Condition	Specified Condition
A49-11 (CANH) - A49-22 (CANL)	Cable disconnected from negative (-) auxiliary battery terminal	1 MΩ or higher

REPLACE ECM

REPAIR OR REPLACE CAN MAIN BUS LINES OR CONNECTOR (NO. 2 CAN JUNCTION CONNECTOR - ECM)

3.	CHECK FOR SHORT IN CAN BUS LINES (NO. 4 CAN JUNCTION CONNECTOR - NO. 2 CAN JUNCTION CONNECTOR)

(a) Disconnect the G96 No. 4 CAN junction connector.

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

Front view of wire harness connector

(to No. 4 CAN Junction Connector)

to Hybrid Vehicle Control ECU

to No. 2 CAN Junction Connector

Standard Resistance:

Tester Connection	Condition	Specified Condition	Connected to
G96-9 (CANH) - G96-20 (CANL)	Cable disconnected from negative (-) auxiliary battery terminal	200 Ω or higher	Hybrid vehicle control ECU
G96-11 (CANH) - G96-22 (CANL)	Cable disconnected from negative (-) auxiliary battery terminal	1 MΩ or higher	No. 2 CAN junction connector

Result	Proceed to
OK	A
NG (Line to No. 2 CAN junction connector)	B
NG (Line to ECU or sensor)	C

REPAIR OR REPLACE CAN MAIN BUS LINES OR CONNECTOR (NO. 4 CAN JUNCTION CONNECTOR - NO. 2 CAN JUNCTION CONNECTOR)

GO TO STEP 6

4.	CHECK FOR SHORT IN CAN BUS LINES (NO. 4 CAN JUNCTION CONNECTOR)

(a) Disconnect the G95 No. 4 CAN junction connector.

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

Front view of wire harness connector

(to No. 4 CAN Junction Connector)

to Central Gateway ECU (Network Gateway ECU)

Standard Resistance:

Tester Connection	Condition	Specified Condition
G95-1 (CANH) - G95-12 (CANL)	Cable disconnected from negative (-) auxiliary battery terminal	108 to 132 Ω

REPLACE NO. 4 CAN JUNCTION CONNECTOR

5.	CHECK FOR SHORT IN CAN BUS LINES (NO. 4 CAN JUNCTION CONNECTOR - CENTRAL GATEWAY ECU (NETWORK GATEWAY ECU))

(a) Disconnect the G52 central gateway ECU (network gateway ECU) connector.

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

Front view of wire harness connector

(to No. 4 CAN Junction Connector)

to Central Gateway ECU (Network Gateway ECU)

Standard Resistance:

Tester Connection	Condition	Specified Condition
G95-1 (CANH) - G95-12 (CANL)	Cable disconnected from negative (-) auxiliary battery terminal	1 MΩ or higher

REPLACE CENTRAL GATEWAY ECU (NETWORK GATEWAY ECU)

REPAIR OR REPLACE CAN MAIN BUS LINES OR CONNECTOR (NO. 4 CAN JUNCTION CONNECTOR - CENTRAL GATEWAY ECU (NETWORK GATEWAY ECU))

6.	CHECK FOR SHORT IN CAN BUS LINES (ECU OR SENSOR)

(a) Reconnect all wire harness connectors.

(b) Disconnect the connector that includes terminals CANH and CANL from the ECU or sensor to which the short circuited branch line is connected.

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Standard Resistance:

Tester Connection	Condition	Specified Condition
G52-18 (CA4H) - G52-17 (CA4L)	Cable disconnected from negative (-) auxiliary battery terminal	54 to 69 Ω

HINT:

If the resistance becomes normal (between 54 and 69 Ω) when the connector is disconnected from the ECU or sensor, there may be a short in the ECU or sensor.
If the resistance does not become normal when the connector is disconnected from the ECU or sensor, check for a short in the wire harness and repair or replace the wire harness or connector if necessary.

*a	Component with harness connected (Central Gateway ECU (Network Gateway ECU))

REPLACE ECU OR SENSOR

REPAIR OR REPLACE HARNESS OR CONNECTOR

Check Bus 2 Line for Short to GND

Check Bus 3 Line for Short to +B. Check Bus 3 Line for Short to GND. Check Bus 3 Lines for Short Circuit

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