Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual: Antenna Coil Open / Short (B2784)

Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual / Vehicle Interior / Theft Deterrent / Keyless Entry / Immobiliser System / Antenna Coil Open / Short (B2784)

DESCRIPTION

When an open or short circuit is detected in the transponder key amplifier coil built into the engine switch, the certification ECU (smart key ECU assembly) stores this DTC. This DTC is also stored as a history DTC.

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

Note

B2784

Antenna Coil Open / Short

The transponder key amplifier coil built into the engine switch is open (see below) or shorted (determined by communication with certification ECU (smart key ECU assembly)). (1 trip detection logic*)

  • Terminal AGND, VC5, TXCT or CODE circuit is open (including disconnection of the engine switch).
  • The transponder key amplifier coil built into the engine switch is open.
  • Engine switch
  • Certification ECU (smart key ECU assembly)
  • Wire harness or connector

DTC output confirmation operation:

  • With the shift lever in P and the electrical key transmitter sub-assembly held near the engine switch, an engine start operation is performed by pressing and holding the engine switch when the transmitter battery is depleted.
  • *: Only output while a malfunction is present.
Vehicle Condition and Fail-safe Operation when Malfunction Detected

Vehicle Condition when Malfunction Detected

Fail-safe Operation when Malfunction Detected

Engine cannot be started when transmitter battery is depleted by holding electrical key transmitter sub-assembly near engine switch and pressing and holding engine switch with shift lever in P

-
Related Data List and Active Test

DTC No.

Data List and Active Test

B2784

-

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.
  • Before replacing the certification ECU (smart key ECU assembly), refer to Registration.

    Click here

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

PROCEDURE

1.

CLEAR DTC

(a) Clear the DTCs.

Body Electrical > Smart Access > Clear DTCs
NEXT

2.

CHECK FOR DTC

(a) Perform "DTC Output Confirmation Operation" procedure.

(b) Check for DTCs.

Body Electrical > Smart Access > Trouble Codes

OK:

DTC B2784 is not output.

OK

USE SIMULATION METHOD TO CHECK

NG

3.

CHECK ENGINE SWITCH (OUTPUT)

(a) Using an oscilloscope, check the waveform.

*a

Component with harness connected

(Engine Switch)

*b

Waveform

*c

Waveform (detail)

-

-

Measurement Condition:

Tester Connection

Condition

Tool Setting

Specified Condition

J14-8 (CODE) - J14-6 (AGND)

Engine switch off, engine switch pressed with electrical key transmitter sub-assembly held near engine switch*

1 V/DIV., 20 ms./DIV.

Pulse generation

(See waveform)

2 V/DIV., 100 μs./DIV.

Pulse generation

(See waveform (detail))
  • *: Remove the transmitter battery before performing this inspection.

OK:

The waveform is similar to that shown in the illustration

NG

REPLACE ENGINE SWITCH

OK

4.

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

(a) Replace the certification ECU (smart key ECU assembly) with a new one.

Click here

NEXT

5.

REGISTER ECU COMMUNICATION ID

(a) Register the ECU communication ID code.

Click here

NEXT

6.

CLEAR DTC

(a) Clear the DTCs.

Body Electrical > Smart Access > Clear DTCs
NEXT

7.

CHECK FOR DTC

(a) Perform "DTC Output Confirmation Operation" procedure.

(b) Check for DTCs.

Body Electrical > Smart Access > Trouble Codes

OK:

DTC B2784 is not output.

OK

END (CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) WAS DEFECTIVE)
NG

REPLACE ENGINE SWITCH

    Short to GND in Immobiliser System Power Source Circuit (B278A)
    DESCRIPTION When there is a short to GND in the power supply for the transponder key amplifier of the engine switch, the certification ECU (smart key ECU assembly) stores this DTC. DTC No. Detect ...

    ID BOX EEPROM Malfunction (B2790)
    DESCRIPTION When an internal malfunction occurs in the ID code box (immobiliser code ECU), the certification ECU (smart key ECU assembly) stores this DTC. DTC No. Detection Item DTC Detection C ...

    Other materials:

    Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual > Lighting System (w/ Automatic Headlight Beam Level Control System): How To Proceed With Troubleshooting
    CAUTION / NOTICE / HINT HINT: Use the following procedure to troubleshoot the lighting system. *: Use the Techstream. PROCEDURE 1. VEHICLE BROUGHT TO WORKSHOP NEXT 2. CUSTOMER PROBLEM ANALYSIS HINT: In troubleshooting, confirm that the problem symptoms h ...

    Lexus RX (RX 350L, RX450h) 2016-2025 Repair Manual > Power Steering System: Dtc Check / Clear
    DTC CHECK / CLEAR CHECK DTCs (USING TECHSTREAM) (a) Turn the engine switch off. (b) Connect the Techstream to the DLC3. (c) Turn the engine switch on (IG). (d) Turn the Techstream on. (e) Enter the following menus: Chassis / EMPS / Trouble Codes. Chassis > EMPS > Trouble Codes (f) Check the de ...

    Lexus RX (RX 350L, RX450h) 2016-{YEAR} Owners Manual

    Lexus RX (RX 350L, RX450h) 2016-{YEAR} Repair Manual

    © 2025 Copyright www.lexusrx.net
    0.0107