Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual: Brake Signal Malfunction (B2284)

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) / Brake Signal Malfunction (B2284)

DESCRIPTION

This DTC is stored when the brake signal sent via direct line and the brake signal sent via CAN communication do not match.

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

Note

B2284

Brake Signal Malfunction

The brake signal sent via direct line and the brake signal sent via CAN communication do not match. (1-trip detection logic*)
  • AM2 fuse
  • STOP fuse
  • Stop light switch assembly
  • SFI system
  • Certification ECU (smart key ECU assembly)
  • Wire harness or connector
  • Connect the cable to the negative (-) battery terminal, release the brake pedal and wait at least 20 seconds. Then depress the brake pedal for 20 seconds or more.
  • *: Only detected while a malfunction is present and the engine switch is on (IG).
Vehicle Condition and Fail-safe Function when Malfunction Detected

Vehicle Condition when Malfunction Detected

Fail-safe Function when Malfunction Detected

With the electrical key transmitter sub-assembly in the cabin, even if an engine start operation is performed, the engine does not start (the key indicator display is not displayed on the multi-information display). However, the engine can be started by turning the engine switch on (ACC) and then pressing and holding it.

  • If there is a malfunction when the brake signal sent via direct line is on, the engine can be started by pressing the engine switch with the brake pedal released.
  • If there is a malfunction when the brake signal sent via direct line is off, the engine cannot be started by pressing the engine switch with the brake pedal depressed.

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Related Data List and Active Test Items

DTC No.

Data List and Active Test

B2284
Power Source Control
  • Stop Light Switch1
Engine
  • Stop Light SW

WIRING DIAGRAM

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.

    Click here

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

    Click here

  • After repair, confirm that no DTCs are output by performing "DTC Output Confirmation Operation".

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.

READ VALUE USING TECHSTREAM (STOP LIGHT SWITCH1)

(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 / Power Source Control / Data List.

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

Body Electrical > Power Source Control > Data List

Tester Display

Measurement Item

Range

Normal Condition

Diagnostic Note

Stop Light Switch1

State of brake pedal

OFF or ON

OFF: Brake pedal released

ON: Brake pedal depressed
  • Use this item to determine if the stop light switch assembly is malfunctioning.
  • The engine cannot be started when this item is OFF.
  • If the stop light switch assembly is malfunctioning, the engine can be started by pressing and holding the engine switch for a certain period of time.
Body Electrical > Power Source Control > Data List

Tester Display

Stop Light Switch1

OK:

The Techstream display changes correctly in response to the brake pedal operation.

OK

GO TO SFI SYSTEM (HOW TO PROCEED WITH TROUBLESHOOTING)

NG

2.

CHECK HARNESS AND CONNECTOR (POWER SOURCE)

Click here

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR IN CIRCUIT CONNECTED TO POWER SOURCE
OK

3.

CHECK HARNESS AND CONNECTOR (GROUND)

Click here

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

4.

CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) - STOP LIGHT SWITCH ASSEMBLY)

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

(b) Disconnect the A55 stop light switch assembly connector.

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

A55-1 (B) - Body ground

Always

11 to 14 V

*a

Front view of wire harness connector

(to Stop Light Switch Assembly)

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

R1-25 (STP1) - A55-2 (L)

Always

Below 1 Ω

A55-3 (GND) - Body ground

Always

Below 1 Ω
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

5.

CHECK CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

(a) Reconnect the J41 and R1 certification ECU (smart Key ECU assembly) connectors.

(b) Reconnect the A55 stop light switch assembly connector.

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

Standard Voltage:

Tester Connection

Condition

Specified Condition

R1-25 (STP1) - Body ground

Brake pedal released → depressed

1 V or less → 9 V or higher

*a

Component with harness connected

(Certification ECU (Smart Key ECU Assembly))
OK

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

NG

REPLACE STOP LIGHT SWITCH ASSEMBLY

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