Lexus NX manuals

Lexus NX: Open in Bus 3 Main Bus Line

Lexus NX Service Manual / Power Source & Network / Networking / Can Communication System / Open in Bus 3 Main Bus Line

DESCRIPTION

There may be an open circuit in one of the CAN main bus lines when the resistance between terminals 6 (CA3H) and 21 (CA3L) of the central gateway ECU (network gateway ECU) is 70 Ω or higher.

Symptom

Trouble Area
  • Resistance between terminals 6 (CA3H) and 21 (CA3L) of the central gateway ECU (network gateway ECU) is 70 Ω or higher.
  • Resistance between terminals 19 (CAYH) and 20 (CAYL) of the central gateway ECU (network gateway ECU) is 70 Ω or higher.
  • CAN main bus wire or connector
  • Central gateway ECU (network gateway ECU)
  • No. 10 CAN junction connector

This malfunction is not related to the lines of a CAN branch or to ECUs or sensors connected to a CAN branch.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

CAUTION:

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

NOTICE:

  • Inspect the fuses for circuits related to this system before performing the following procedure.
  • 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.

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  • When disconnecting and reconnecting the auxiliary battery.

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    HINT:

    When disconnecting and reconnecting the auxiliary battery, there is an automatic learning function that completes learning when the respective system is used.

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  • Some parts must be initialized and set when replacing or removing and installing parts.

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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 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:

  • Operating the power switch, any switches or any doors triggers related ECU and sensor communication with the CAN, which causes resistance variation.
  • 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 OPEN IN CAN BUS WIRE (NO. 10 CAN JUNCTION CONNECTOR)

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

(b) Disconnect the No. 10 CAN junction connector.

*a

Front view of wire harness connector

(to No. 10 CAN Junction Connector)

*b

to Central Gateway ECU (Network Gateway ECU)

*c

to Central Gateway ECU (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

I164-1 (CANH) - I164-12 (CANL)

Cable disconnected from negative (-) auxiliary battery terminal

108 to 132 Ω

Central gateway ECU (network gateway ECU)

I164-5 (CANH) - I164-16 (CANL)

Cable disconnected from negative (-) auxiliary battery terminal

108 to 132 Ω

Central gateway ECU (network gateway ECU)
OK

REPLACE NO. 10 CAN JUNCTION CONNECTOR
NG

2.

CHECK FOR OPEN IN CAN BUS WIRE (CENTRAL GATEWAY ECU [NETWORK GATEWAY ECU] - NO. 10 CAN JUNCTION CONNECTOR)

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

I160-6 (CA3H) - I160-21 (CA3L)

Cable disconnected from negative (-) auxiliary battery terminal

108 to 132 Ω

I160-19 (CAYH) - I160-20 (CAYL)

*a

Component with harness connected

(Central Gateway ECU [Network Gateway ECU])
OK

REPAIR OR REPLACE CAN MAIN WIRE OR CONNECTOR (CENTRAL GATEWAY ECU [NETWORK GATEWAY ECU] - NO. 10 CAN JUNCTION CONNECTOR)
NG

REPLACE CENTRAL GATEWAY ECU (NETWORK GATEWAY ECU)

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