Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual: Power Source Mode does not Change to ON (ACC)

Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual / Vehicle Interior / Theft Deterrent / Keyless Entry / Smart Access System With Push-button Start (for Start Function) / Power Source Mode does not Change to ON (ACC)

DESCRIPTION

If the engine switch is pressed with the electrical key transmitter sub-assembly in the cabin, the certification ECU (smart key ECU assembly) receives a signal and changes the power source mode.

Related Data List and Active Test Items

Problem Symptom

Data List and Active Test

Power source mode does not change to on (ACC) but does change to on (IG)
Power Source Control
  • Power Supply Condition
  • ACC Relay Monitor
Starting Control
  • Ignition

WIRING DIAGRAM

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CAUTION / NOTICE / HINT

NOTICE:

  • When using the Techstream with the engine switch off, connect the Techstream to the DLC3 and turn a courtesy light switch on and off at intervals of 1.5 seconds or less until communication between the Techstream and the vehicle begins. Then select the vehicle type under manual mode and enter the following menus: Body Electrical / Smart Access. While using the Techstream, periodically turn a courtesy light switch on and off at intervals of 1.5 seconds or less to maintain communication between the Techstream and the vehicle.
  • The smart access system with push-button start (for Start Function) uses the LIN communication system and CAN communication system. Inspect the communication function by following How to Proceed with Troubleshooting. Troubleshoot the smart access system with push-button start (for Start Function) after confirming that the communication systems are functioning properly.

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  • Make sure that no DTCs are output. If any DTCs are output, proceed to Diagnostic Trouble Code Chart.
  • If the smart access system with push-button start (for Start Function) has been canceled, enable the system before performing troubleshooting.

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  • Inspect the fuses for circuits related to this system before performing the following procedure.
  • Before replacing the certification ECU (smart key ECU assembly), refer to smart access system with push-button start (for Start Function) Precaution.

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  • After completing repairs, confirm that the problem does not recur.

HINT:

When the cable is disconnected and reconnected to the negative (-) battery terminal, the power source mode returns to the state it was in before the cable was disconnected.

PROCEDURE

1.

CHECK FOR DTC

(a) Using the Techstream, check for certification ECU (smart key ECU assembly) DTCs.

Body Electrical > Power Source Control > Trouble Codes Body Electrical > Smart Access > Trouble Codes Body Electrical > Starting Control > Trouble Codes

Result

Proceed to

DTCs are not output

A

Smart access system with push-button start (for Start Function) DTCs are output

B
B

GO TO DIAGNOSTIC TROUBLE CODE CHART

A

2.

CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) - INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY)

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NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

3.

INSPECT INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY (ACC RELAY)

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NG

REPLACE INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY

OK

4.

CHECK CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

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OK

USE SIMULATION METHOD TO CHECK

NG

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

    Power Source Mode does not Change to ON (IG)
    DESCRIPTION If the engine switch is pressed with the electrical key transmitter sub-assembly in the cabin, the certification ECU (smart key ECU assembly) receives a signal and changes the power source ...

    Theft Deterrent System
    ...

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