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

Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual / Power Source & Network / Networking / Can Communication System / Check Bus 3 Line for Short to +B

DESCRIPTION

There may be a short circuit between one of the CAN bus lines and +B when there is no resistance between terminal 6 (CA3H) of the network gateway ECU and terminal 16 (BAT) of the DLC3, or terminal 21 (CA3L) of the network gateway ECU and terminal 16 (BAT) of the DLC3.

Symptom

Trouble Area

There is no resistance between terminal 6 (CA3H) of the network gateway ECU and terminal 16 (BAT) of the DLC3, or terminal 21 (CA3L) of the network gateway ECU and terminal 16 (BAT) 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.

    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 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.

    Click here

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 +B IN CAN BUS LINE (NETWORK GATEWAY ECU)

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

(b) Disconnect the J75 network gateway ECU connector.

*1

DLC3

-

-

*a

Front view of wire harness connector

(to Network Gateway ECU)

-

-

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

J75-6 (CA3H) - J141-16 (BAT)

Cable disconnected from negative (-) battery terminal

6 kΩ or higher

J75-21 (CA3L) - J141-16 (BAT)
OK

REPLACE NETWORK GATEWAY ECU

NG

2.

CHECK FOR SHORT TO +B 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

-

-

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

Connected to

J98-7 (CANH) - J141-16 (BAT)

Cable disconnected from negative (-) battery terminal

6 kΩ or higher

Network gateway ECU

J98-18 (CANL) - J141-16 (BAT)

J98-9 (CANH) - J141-16 (BAT)

Cable disconnected from negative (-) battery terminal

6 kΩ or higher

DCM (telematics transceiver)*

J98-20 (CANL) - J141-16 (BAT)

J98-10 (CANH) - J141-16 (BAT)

Cable disconnected from negative (-) battery terminal

6 kΩ or higher

Radio receiver assembly

J98-21 (CANL) - J141-16 (BAT)

J98-11 (CANH) - J141-16 (BAT)

Cable disconnected from negative (-) battery terminal

6 kΩ or higher

Network gateway ECU

J98-22 (CANL) - J141-16 (BAT)
  • *: w/ Manual (SOS) Switch

Result

Proceed to

OK

A

NG (Network gateway ECU main line)

B

NG (ECU or sensor bus line)

C
A

REPLACE NO. 6 CAN JUNCTION CONNECTOR
B

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

3.

CHECK FOR SHORT TO +B 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 +B is connected.

Click here

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

*1

DLC3

-

-

*a

Component with harness connected

(Network Gateway ECU)

-

-

Standard Resistance:

Tester Connection

Condition

Specified Condition

J75-6 (CA3H) - J141-16 (BAT)

Cable disconnected from negative (-) battery terminal

6 kΩ or higher

J75-21 (CA3L) - J141-16 (BAT)

HINT:

If the resistance changes to 6 kΩ or higher when the connector is disconnected from the ECU or sensor, there may be a short in the ECU or sensor.

OK

REPLACE CORRESPONDING ECU OR SENSOR
NG

REPAIR OR REPLACE CORRESPONDING ECU OR SENSOR CAN BUS LINE OR CONNECTOR
    Check Bus 3 Lines for Short Circuit
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