Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual: Check Bus 3 Lines for Short Circuit

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

DESCRIPTION

There may be a short circuit between the bus 3 main lines and/or bus 3 branch lines when the resistance between terminals 6 (CA3H) and 21 (CA3L) of the network gateway ECU is below 54 Ω.

Symptom

Trouble Area

Resistance between terminals 6 (CA3H) and 21 (CA3L) of network gateway ECU is below 54 Ω.
  • 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 IN CAN BUS LINES (NO. 6 CAN JUNCTION CONNECTOR)

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

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

*a

Front view of wire harness connector

(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) - J98-18 (CANL)

Cable disconnected from negative (-) battery terminal

108 to 132 Ω

Network gateway ECU

J98-9 (CANH) - J98-20 (CANL)

Cable disconnected from negative (-) battery terminal

200 Ω or higher

DCM (telematics transceiver)*

J98-10 (CANH) - J98-21 (CANL)

Cable disconnected from negative (-) battery terminal

200 Ω or higher

Radio receiver assembly

J98-11 (CANH) - J98-22 (CANL)

Cable disconnected from negative (-) battery terminal

108 to 132 Ω

Network gateway ECU
  • *: w/ Manual (SOS) Switch

Result

Proceed to

OK

A

NG (Network gateway ECU main lines)

B

NG (ECU or sensor branch lines)

C
A

REPLACE NO. 6 CAN JUNCTION CONNECTOR
C

GO TO STEP 3

B

2.

CHECK FOR SHORT IN CAN BUS LINES (NETWORK GATEWAY ECU)

(a) Disconnect the J75 network gateway ECU connector.

*a

Front view of wire harness connector

(to Network Gateway ECU)

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

J75-6 (CA3H) - J75-21 (CA3L)

Cable disconnected from negative (-) battery terminal

1 MΩ or higher

J75-19 (CAYH) - J75-20 (CAYL)

Cable disconnected from negative (-) battery terminal

1 MΩ or higher
OK

REPLACE NETWORK GATEWAY ECU

NG

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

3.

CHECK FOR SHORT IN CAN BUS LINES (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 short circuited branch line is connected.

Click here

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

J75-6 (CA3H) - J75-21 (CA3L)

Cable disconnected from negative (-) 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.

*a

Component with harness connected

(Network Gateway ECU)
OK

REPLACE CORRESPONDING ECU OR SENSOR
NG

REPAIR OR REPLACE CORRESPONDING ECU OR SENSOR BRANCH LINES OR CONNECTOR
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