Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual: Check Bus 3 Line for Short to GND

Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual / Power Source & Network / Networking / Can Communication System / 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 network gateway ECU and terminal 4 (CG) of the DLC3, or terminal 21 (CA3L) of the network gateway ECU and terminal 4 (CG) of the DLC3.

Symptom	Trouble Area
There is no resistance between terminal 6 (CA3H) of the network gateway ECU and terminal 4 (CG) of the DLC3, or terminal 21 (CA3L) of the network gateway ECU and terminal 4 (CG) of the DLC3.	Short in CAN main bus line Short in CAN branch line DCM (telematics transceiver) (w/ Manual (SOS) Switch) Radio receiver assembly Network gateway ECU No. 6 CAN junction connector

WIRING DIAGRAM

CAUTION / NOTICE / HINT

CAUTION:

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

NOTICE:

Before measuring the resistance of the CAN bus, turn the engine 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 engine 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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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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After performing repairs, perform the DTC check procedure and confirm that the DTCs are not output again.
DTC check procedure: Turn the engine 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.
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HINT:

Operating the engine 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 SHORT TO GND IN CAN BUS LINE (NETWORK GATEWAY ECU)

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

(b) Disconnect the J75 network gateway ECU connector.

DLC3

Front view of wire harness connector

(to Network Gateway ECU)

Standard Resistance:

Tester Connection	Condition	Specified Condition
J75-6 (CA3H) - J141-4 (CG)	Cable disconnected from negative (-) battery terminal	200 Ω or higher
J75-21 (CA3L) - J141-4 (CG)	Cable disconnected from negative (-) battery terminal	200 Ω or higher

REPLACE NETWORK GATEWAY ECU

2.	CHECK FOR SHORT TO GND IN CAN BUS LINE (NO. 6 CAN JUNCTION CONNECTOR)

(a) Reconnect the J75 network gateway ECU connector.

(b) Disconnect the J98 No. 6 CAN junction connector.

*1	DLC3	-	-
*a	Front view of wire harness connector (to No. 6 CAN Junction Connector)	*b	to Network Gateway ECU
*c	to DCM (Telematics Transceiver) (w/ Manual (SOS) Switch)	*d	to Radio Receiver Assembly
*e	to Network Gateway ECU	-	-

Standard Resistance:

Tester Connection	Condition	Specified Condition	Connected to
J98-7 (CANH) - J141-4 (CG)	Cable disconnected from negative (-) battery terminal	200 Ω or higher	Network gateway ECU
J98-18 (CANL) - J141-4 (CG)	Cable disconnected from negative (-) battery terminal	200 Ω or higher	Network gateway ECU
J98-9 (CANH) - J141-4 (CG)	Cable disconnected from negative (-) battery terminal	200 Ω or higher	DCM (telematics transceiver)*
J98-20 (CANL) - J141-4 (CG)	Cable disconnected from negative (-) battery terminal	200 Ω or higher	DCM (telematics transceiver)*
J98-10 (CANH) - J141-4 (CG)	Cable disconnected from negative (-) battery terminal	200 Ω or higher	Radio receiver assembly
J98-21 (CANL) - J141-4 (CG)	Cable disconnected from negative (-) battery terminal	200 Ω or higher	Radio receiver assembly
J98-11 (CANH) - J141-4 (CG)	Cable disconnected from negative (-) battery terminal	200 Ω or higher	Network gateway ECU
J98-22 (CANL) - J141-4 (CG)	Cable disconnected from negative (-) battery terminal	200 Ω or higher	Network gateway ECU

*: w/ Manual (SOS) Switch

Result	Proceed to
OK	A
NG (Network gateway ECU main line)	B
NG (ECU or sensor bus line)	C

REPLACE NO. 6 CAN JUNCTION CONNECTOR

REPAIR OR REPLACE CAN MAIN BUS LINE OR CONNECTOR (NO. 6 CAN JUNCTION CONNECTOR - NETWORK GATEWAY ECU)

3.	CHECK FOR SHORT TO GND IN CAN BUS LINE (ECU, 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 bus line shorted to GND is connected.

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DLC3

Component with harness connected

(Network Gateway ECU)

Standard Resistance:

Tester Connection	Condition	Specified Condition
J75-6 (CA3H) - J141-4 (CG)	Cable disconnected from negative (-) battery terminal	200 Ω or higher
J75-21 (CA3L) - J141-4 (CG)	Cable disconnected from negative (-) battery terminal	200 Ω or higher

HINT:

If the resistance changes to 200 Ω or higher when the connector is disconnected from the ECU or sensor, there may be a short in the ECU or sensor.

REPLACE CORRESPONDING ECU OR SENSOR

REPAIR OR REPLACE CORRESPONDING ECU OR SENSOR CAN BUS LINE OR CONNECTOR

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Check Bus 3 Line for Short to +B

Open in One Side of Bus 3 Branch Line

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