Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual: Engine/Power Switch Malfunction (B2278)

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) / Engine/Power Switch Malfunction (B2278)

DESCRIPTION

This DTC is stored when the SSW1 contact signal and SSW2 contact signal, which are detected when the engine switch is operated, do not match.

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

Note

B2278

Engine/Power Switch Malfunction

When the engine switch is operated, the SSW1 contact signal and SSW2 contact signal do not match (1-trip detection logic*).
  • AM2 fuse
  • Engine switch
  • Certification ECU (smart key ECU assembly)
  • Wire harness or connector
  • Turn the engine switch on (IG).
  • *: Only detected while a malfunction is present.
Vehicle Condition and Fail-safe Function when Malfunction Detected

Vehicle Condition when Malfunction Detected

Fail-safe Function when Malfunction Detected

If either the SSW1 contact signal or SSW2 contact signal is stuck on, the power source mode cannot be changed by pressing the engine switch. If either the SSW1 contact signal or SSW2 contact signal is stuck off, emergency stop by pressing and holding the engine switch for 2 seconds or more cannot be operated.

-
Related Data List and Active Test Items

DTC No.

Data List and Active Test

B2278
Power Source Control
  • Starter Switch1
  • Starter Switch2

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 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 (START SWITCH1, START SWITCH2)

(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

Start Switch1

Engine switch 1 status

OFF or ON

OFF: Engine switch not pressed

ON: Engine switch pressed
  • If the engine switch is pressed for a short time, the display may not change.
  • Use this item to determine if the engine switch input signal is malfunctioning.

Start Switch2

Engine switch 2 status

OFF or ON

OFF: Engine switch not pressed

ON: Engine switch pressed
  • Backup for engine switch 1. However, when the engine switch is pressed and held, the power source mode can only be changed when both engine switch 1 and 2 are normal.
  • Behaves the same way as engine switch 1.
Body Electrical > Power Source Control > Data List

Tester Display

Start Switch1

Start Switch2

OK:

The Techstream display changes correctly in response to the engine switch operation.

NG

GO TO STEP 3

OK

2.

READ VALUE USING TECHSTREAM (START SWITCH1, START SWITCH2)

(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) According to the display on the Techstream, read the Data List while wiggling the wire harness.

Body Electrical > Power Source Control > Data List

Tester Display

Measurement Item

Range

Normal Condition

Diagnostic Note

Start Switch1

Engine switch 1 status

OFF or ON

OFF: Engine switch not pressed

ON: Engine switch pressed
  • If the engine switch is pressed for a short time, the display may not change.
  • Use this item to determine if the engine switch input signal is malfunctioning.

Start Switch2

Engine switch 2 status

OFF or ON

OFF: Engine switch not pressed

ON: Engine switch pressed
  • Backup for engine switch 1. However, when the engine switch is pressed and held, the power source mode can only be changed when both engine switch 1 and 2 are normal.
  • Behaves the same way as engine switch 1.
Body Electrical > Power Source Control > Data List

Tester Display

Start Switch1

Start Switch2

OK:

The Techstream display changes correctly in response to the engine switch operation.

OK

USE SIMULATION METHOD TO CHECK

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

3.

CHECK HARNESS AND CONNECTOR (POWER SOURCE)

Click here

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

4.

CHECK HARNESS AND CONNECTOR (GROUND)

Click here

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

5.

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

(a) Disconnect the J14 engine switch connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

J41-23 (SSW1) - J14-5 (SS1)

Always

Below 1 Ω

J41-21 (SSW2) - J14-1 (SS2)

Always

Below 1 Ω

J41-11 (AGND) - J14-6 (AGND)

Always

Below 1 Ω

J41-23 (SSW1) or J14-5 (SS1) - Body ground

Always

10 kΩ or higher

J41-21 (SSW2) or J14-1 (SS2) - Body ground

Always

10 kΩ or higher

J41-11 (AGND) or J14-6 (AGND) - Body ground

Always

10 kΩ or higher
NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

6.

INSPECT ENGINE SWITCH

(a) Remove the engine switch.

Click here

(b) Inspect the engine switch.

Click here

OK

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

NG

REPLACE ENGINE SWITCH

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