Lexus RX (RX 350L, RX450h) 2016-2024 Repair Manual: Check Bus 2 Lines for Short Circuit

DESCRIPTION

There may be a short circuit between the bus 2 main lines and/or bus 2 branch lines when the resistance between terminals 18 (CA4H) and 17 (CA4L) of the network gateway ECU is below 54 Ω.

Symptom

Trouble Area

Resistance between terminals 18 (CA4H) and 17 (CA4L) of network gateway ECU is below 54 Ω.

  • Short in CAN main bus line
  • Short in CAN branch line
  • Network gateway ECU
  • ECM

WIRING DIAGRAM

CAUTION / NOTICE / HINT

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: Drive the vehicle at a speed of 60 km/h (37 mph) or more for 5 minutes or more. And drive the vehicle with the dynamic radar cruise control system operated for 4 seconds 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 IN CAN BUS LINES (NETWORK GATEWAY ECU)

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

(b) Disconnect the J75 network gateway ECU connector.

*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

J75-18 (CA4H) - J75-17 (CA4L)

Cable disconnected from negative (-) battery terminal

108 to 132 Ω

OK

REPLACE NETWORK GATEWAY ECU

NG

2.

CHECK FOR SHORT IN CAN BUS LINES (ECM)

(a) Reconnect the J75 network gateway ECU connector.

(b) Disconnect the A37 ECM connector.

*a

Front view of wire harness connector

(to ECM)

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

A37-13 (CANH) - A37-26 (CANL)

Cable disconnected from negative (-) battery terminal

108 to 132 Ω

OK

REPLACE ECM

NG

REPAIR OR REPLACE CAN MAIN BUS LINES OR CONNECTOR (ECM - NETWORK GATEWAY ECU)

    Open in Bus 2 Main Bus Line
    DESCRIPTION There may be an open circuit in one of the bus 2 main lines when the resistance between terminals 18 (CA4H) and 17 (CA4L) of the network gateway ECU is 70 Ω or higher. Symptom Troubl ...

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    DESCRIPTION There may be a short circuit between one of the CAN bus lines and +B when no resistance exists between terminal 18 (CA4H) of the network gateway ECU and terminal 16 (BAT) of the DLC3, or t ...

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    Lexus RX (RX 350L, RX450h) 2016-{YEAR} Owners Manual

    Lexus RX (RX 350L, RX450h) 2016-{YEAR} Repair Manual

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