Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual: 4WD Control ECU Communication Stop Mode

Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual / Power Source & Network / Networking / Can Communication System / 4WD Control ECU Communication Stop Mode

DESCRIPTION

Detection Item

Symptom

Trouble Area

4WD Control ECU Communication Stop Mode

Either condition is met:

  • "Four Wheel Drive Control" is not displayed on the CAN Bus Check screen of the Techstream.

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  • Communication system DTCs (DTCs that start with U) that correspond to "4WD Control ECU Communication Stop Mode" in "DTC Combination Table" are output.

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  • 4WD ECU assembly branch line or connector
  • Power source circuit of 4WD ECU assembly
  • 4WD ECU assembly ground circuit
  • 4WD ECU assembly

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: Turn the engine switch on (IG) and wait for at least 61 seconds., and then drive the vehicle at a speed of 60 km/h (37 mph) or more 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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  • Inspect the fuses for circuits related to this system before performing the following procedure.

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 OPEN IN CAN BUS LINES (4WD ECU ASSEMBLY BRANCH LINE)

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

(b) Disconnect the R10 4WD ECU assembly connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

R10-6 (CANH) - R10-5 (CANL)

Cable disconnected from negative (-) battery terminal

54 to 69 Ω

*a

Front view of wire harness connector

(to 4WD ECU Assembly)
NG

REPAIR OR REPLACE CAN BRANCH LINES OR CONNECTOR (4WD ECU ASSEMBLY)
OK

2.

CHECK HARNESS AND CONNECTOR (POWER SOURCE CIRCUIT)

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

R10-4 (GND) - Body ground

Cable disconnected from negative (-) battery terminal

Below 1 Ω

*a

Front view of wire harness connector

(to 4WD ECU Assembly)

(b) Reconnect the cable to the negative (-) battery terminal.

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

R10-3 (IG1) - Body ground

Engine switch on (IG)

11 to 14 V
OK

REPLACE 4WD ECU ASSEMBLY

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR (POWER SOURCE CIRCUIT)
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