Lexus NX manuals

Lexus NX: Main Body ECU Communication Stop Mode

Lexus NX Service Manual / Power Source & Network / Networking / Can Communication System / Main Body ECU Communication Stop Mode

DESCRIPTION

Detection Item

Symptom

Trouble Area

Main Body ECU Communication Stop Mode

Any of the following conditions are met:

  • Communication stop for "Main Body" is indicated on the "Communication Bus Check" screen of the Techstream.

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  • Communication system DTCs (DTCs that start with U) that correspond to "Main Body ECU Communication Stop Mode" in "DTC Combination Table" are output.

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  • Main body ECU (multiplex network body ECU) branch wire or connector
  • Power source circuit of main body ECU (multiplex network body ECU) or instrument panel junction block assembly
  • Main body ECU (multiplex network body ECU) or instrument panel junction block assembly ground circuit
  • Main body ECU (multiplex network body ECU) or instrument panel junction block assembly

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 (MAIN BODY ECU [MULTIPLEX NETWORK BODY ECU] BRANCH WIRE)

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

(b) Disconnect the main body ECU (multiplex network body ECU) connector.

*a

Front view of wire harness connector

(to Main Body ECU [Multiplex Network Body ECU])

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

I48-14 (CANH) - I48-13 (CANL)

Cable disconnected from negative (-) auxiliary battery terminal

54 to 69 Ω
NG

REPAIR OR REPLACE CAN BRANCH WIRE OR CONNECTOR
OK

2.

CHECK HARNESS AND CONNECTOR (POWER SOURCE CIRCUIT)

(a) Reconnect the cable to the negative (-) auxiliary battery terminal.

*a

Component without harness connected

(Instrument Panel Junction Block Assembly)

(b) Remove the instrument panel junction block assembly.

Click here

(c) reconnect the instrument panel junction block assembly connectors.

(d) Measure the voltage according to the value(s) in the table below.

Standard Voltage:

Tester Connection

Switch Condition

Specified Condition

A-30 (ACC) - Body ground

Power switch on (ACC)

11 to 14 V

Power switch off

Below 1 V

A-31 (BECU) - Body ground

Power switch off

11 to 14 V

A-32 (IG) - Body ground

Power switch on (IG)

11 to 14 V

Power switch off

Below 1 V

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

A-11 (GND1) - Body ground

Always

Below 1 Ω
OK

REPLACE MAIN BODY ECU (MULTIPLEX NETWORK BODY ECU)

NG

3.

CHECK HARNESS AND CONNECTOR (POWER SOURCE CIRCUIT)

(a) Disconnect the instrument panel junction block assembly connectors.

*a

Front view of wire harness connector

(to Instrument Panel Junction Block Assembly)

-

-

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

Standard Voltage:

Tester Connection

Switch Condition

Specified Condition

4D-49 - Body ground

Power switch off

11 to 14 V

4F-1 - Body ground

Power switch off

11 to 14 V

4C-28 - Body ground

Power switch on (ACC)

11 to 14 V

Power switch off

Below 1 V

4C-44 - Body ground

Power switch on (IG)

11 to 14 V

Power switch off

Below 1 V

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

4D-9 - Body ground

Always

Below 1 Ω
OK

REPLACE INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR (POWER SOURCE CIRCUIT)

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