Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual: Power Steering ECU Communication Stop Mode

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

DESCRIPTION

Detection Item

Symptom

Trouble Area

Power Steering ECU Communication Stop Mode

Either condition is met:

  • "Power Steering (EPS)" 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 "Power Steering ECU Communication Stop Mode" in "DTC Combination Table" are output.

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  • Power steering ECU assembly branch line or connector
  • Power source circuit of power steering ECU assembly
  • Power steering ECU assembly ground circuit
  • Power steering 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: Drive the vehicle at a speed of 20 km/h (12 mph) or more for 5 minutes or more, and with the dynamic radar cruise control system operated for 2.65 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 (POWER STEERING ECU ASSEMBLY BRANCH LINE)

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

(b) Disconnect the J4 power steering ECU assembly connector.

*a

Front view of wire harness connector

(to Power Steering ECU Assembly)

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

J4-7 (CANH) - J4-8 (CANL)

Cable disconnected from negative (-) battery terminal

54 to 69 Ω
NG

REPAIR OR REPLACE CAN BRANCH LINES OR CONNECTOR (POWER STEERING ECU ASSEMBLY)
OK

2.

CHECK HARNESS AND CONNECTOR (POWER SOURCE CIRCUIT)

(a) Disconnect the J5 power steering ECU assembly connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

J5-2 (PGND) - Body ground

Cable disconnected from negative (-) battery terminal

Below 1 Ω

*a

Front view of wire harness connector

(to Power Steering ECU Assembly)

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

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

J4-1 (IG) - Body ground

Engine switch on (IG)

11 to 14 V

*a

Front view of wire harness connector

(to Power Steering ECU Assembly)
OK

REPLACE POWER STEERING ECU ASSEMBLY

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR (POWER SOURCE CIRCUIT)
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