Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual: Back Door Entry Lock Function does not Operate

Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual / Vehicle Interior / Theft Deterrent / Keyless Entry / Smart Access System With Push-button Start (for Entry Function) / Back Door Entry Lock Function does not Operate

DESCRIPTION

If the entry lock function does not operate for the back door only, but the entry unlock function operates, the request code is being transmitted properly from the back door. In this case, there may be a problem related to the lock switch (connection between the back door opener switch assembly and certification ECU (smart key ECU assembly)).

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

  • The smart access system with push-button start (for Entry 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 Entry Function) after confirming that the communication systems are functioning properly.

    Click here

  • 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.
  • Check that there are no electrical key transmitter sub-assemblies in the vehicle.
  • Before replacing the certification ECU (smart key ECU assembly), refer to Precaution.

    Click here

  • After repair, confirm that no DTCs are output.

PROCEDURE

1.

CHECK POWER DOOR LOCK CONTROL SYSTEM

(a) When the door control switch on the multiplex network master switch assembly is operated, check that the doors unlock and lock according to the switch operation.

Click here

OK:

Door locks operate normally.

NG

GO TO POWER DOOR LOCK CONTROL SYSTEM

OK

2.

INSPECT TECHSTREAM (TR/B-DOOR LOCK SW)

(a) Connect the Techstream to the DLC3.

(b) Turn the engine switch on (IG).

(c) Turn the Techstream on.

(d) Enter the following menus: Body Electrical / Smart Access / Data List.

(e) Read the Data List according to the display on the Techstream.

Body Electrical > Smart Access > Data List

Tester Display

Measurement Item

Range

Normal Condition

Diagnostic Note

Tr/B-Door Lock SW

Back door opener switch assembly (lock switch)

ON or OFF

ON: Back door opener switch assembly (lock switch) pressed

OFF: Back door opener switch assembly (lock switch) not pressed
  • Displays whether the back door opener switch assembly (lock switch) is on or off.
  • Use this Data List item to help determine if there is a switch malfunction when the back door lock function does not operate.
Body Electrical > Smart Access > Data List

Tester Display

Tr/B-Door Lock SW

HINT:

When checking the operation of the entry lock function several times, it can be operated up to 2 times consecutively. To operate the function 3 times or more consecutively, the doors need to be unlocked once. However, this is only for the entry lock function, other door lock operations, such as a wireless door lock operation can be performed consecutively.

OK:

The Techstream display changes correctly in response to the operation of the back door opener switch assembly.

OK

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

NG

3.

CHECK HARNESS AND CONNECTOR (BACK DOOR OPENER SWITCH ASSEMBLY - CERTIFICATION ECU (SMART KEY ECU ASSEMBLY))

(a) Disconnect the R1 certification ECU (smart key ECU assembly) connector.

(b) Disconnect the Z8 back door opener switch assembly connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

R1-27 (TSW6) - Z8-1 (L)

Always

Below 1 Ω

Z8-2 (E) - Body ground

Always

Below 1 Ω

R1-27 (TSW6) or Z8-1 (L) - Body ground

Always

10 kΩ or higher
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

4.

INSPECT BACK DOOR OPENER SWITCH ASSEMBLY (LOCK SWITCH)

(a) Remove the back door opener switch assembly.

Click here

(b) Inspect the back door opener switch assembly.

Click here

OK

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

NG

REPLACE BACK DOOR OPENER SWITCH ASSEMBLY

    Back Door Entry Lock and Unlock Functions do not Operate
    DESCRIPTION If the entry lock and unlock functions do not operate for the back door only, the request code may not be being transmitted from the back door. If the entry functions for other doors opera ...

    New Key cannot be Registered
    DESCRIPTION If a new electrical key transmitter sub-assembly could not be registered, wave interference or a malfunction of the certification ECU (smart key ECU assembly), electrical key transmitter s ...

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