Lexus NX: Open in Driver Side Electrical Antenna Circuit (B27A1)

Lexus NX Service Manual / Vehicle Interior / Theft Deterrent / Keyless Entry / Smart Access System With Push-button Start (for Entry Function) / Open in Driver Side Electrical Antenna Circuit (B27A1)

DESCRIPTION

The certification ECU (smart key ECU assembly) generates a request signal and transmits the signal to the front door outside handle assembly (for driver door) (electrical key antenna) at intervals of 0.25 seconds. For the front door outside handle assembly (for driver door) (electrical key antenna) to detect when the electrical key transmitter sub-assembly is brought close to the vehicle, a signal requesting a response from the electrical key transmitter sub-assembly is transmitted within approximately 1 m (3.28 ft.) of the driver door at intervals of 0.25 seconds. DTC B27A1 is stored by the certification ECU (smart key ECU assembly) when an open circuit is detected between the certification ECU (smart key ECU assembly) and front door outside handle assembly (for driver door) (electrical key antenna) (between terminals CLG1 and ANT1, or terminals CG1B and ANT2).

DTC No.	Detection Item	DTC Detection Condition	Trouble Area	Note
B27A1	Open in Driver Side Electrical Antenna Circuit	An open circuit is detected in the circuit between the certification ECU (smart key ECU assembly) and front door outside handle assembly (for driver door) (CLG1 - ANT1, CG1B - ANT2) (This is detected by the malfunction detection circuit in the certification ECU (smart key ECU assembly)) (1 trip detection logic*).	Certification ECU (smart key ECU assembly) Front door outside handle assembly (for driver door) Harness or connector	Any time

*: 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
Entry lock/unlock operation cannot be performed for driver door	-

Related Data List and Active Test

DTC No.	Data List and Active Test
B27A1	Key diagnostic mode can be used to perform troubleshooting

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.
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When using the Techstream with the power 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 smart access system with push-button start (for Entry Function) Precaution.
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After repair, confirm that no DTCs are output by performing "DTC Output Confirmation Operation".

PROCEDURE

1.	CHECK CONNECTOR CONNECTION

(a) Check that the connectors are properly connected to the certification ECU (smart key ECU assembly) and front door outside handle assembly (for driver door).

OK:

Connectors are properly connected.

CONNECT CONNECTORS PROPERLY

2.	CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) - FRONT DOOR OUTSIDE HANDLE ASSEMBLY (FOR DRIVER DOOR))

(a) Disconnect the I53 certification ECU (smart key ECU assembly) connector.

(b) Disconnect the M4 front door outside handle assembly (for driver door) connector.

Standard Resistance:

Tester Connection	Condition	Specified Condition
I53-4 (CLG1) - M4-4 (ANT1)	Always	Below 1 Ω
I53-3 (CG1B) - M4-5 (ANT2)	Always	Below 1 Ω
I53-11 (E) - Body ground	Always	Below 1 Ω
I53-4 (CLG1) or M4-4 (ANT1) - Body ground	Always	10 kΩ or higher
I53-3 (CG1B) or M4-5 (ANT2) - Body ground	Always	10 kΩ or higher

(d) Reconnect the I53 certification ECU (smart key ECU assembly) connector.

REPAIR OR REPLACE HARNESS OR CONNECTOR

3.	CHECK CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) (OUTPUT TO FRONT DOOR OUTSIDE HANDLE ASSEMBLY (FOR DRIVER DOOR))

Component with harness connected

(Certification ECU (Smart Key ECU Assembly))

Waveform 1

Waveform 2

Waveform 3

Waveform 4

(a) Using an oscilloscope, check the waveform.

OK:

Tester Connection	Condition	Tool Setting	Specified Condition
I53-4 (CLG1) - I53-11 (E)	Procedure: Power switch off All doors closed Electrical key transmitter sub-assembly not inside vehicle All doors locked through wireless operation (electrical key transmitter sub-assembly brought inside detection area*)	5 V/DIV., 500 ms/DIV.	Pulse generation (See waveform 1)
I53-4 (CLG1) - I53-11 (E)	Procedure: Power switch off All doors closed Electrical key transmitter sub-assembly not inside vehicle All doors locked through wireless operation (electrical key transmitter sub-assembly brought outside detection area*)	5 V/DIV., 100 ms/DIV.	Pulse generation (See waveform 2)
I53-3 (CG1B) - I53-11 (E)	Procedure: Power switch off All doors closed Electrical key transmitter sub-assembly not inside vehicle All doors locked through wireless operation (electrical key transmitter sub-assembly brought inside detection area*)	5 V/DIV., 500 ms/DIV.	Pulse generation (See waveform 3)
I53-3 (CG1B) - I53-11 (E)	Procedure: Power switch off All doors closed Electrical key transmitter sub-assembly not inside vehicle All doors locked through wireless operation (electrical key transmitter sub-assembly brought outside detection area*)	5 V/DIV., 100 ms/DIV.	Pulse generation (See waveform 4)

*: For details about the entry function detection area, refer to Operation Check.
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REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

4.	REPLACE FRONT DOOR OUTSIDE HANDLE ASSEMBLY (FOR DRIVER DOOR)

(a) Replace the front door outside handle assembly (for driver door) with a new one or the front door outside handle assembly (for front passenger door) if it is functioning properly.

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CLEAR DTC

(a) Clear the DTCs.

Body Electrical > Smart Access > Clear DTCs

6.	CHECK FOR DTC

(a) Check for DTCs.

Body Electrical > Smart Access > Trouble Codes

OK:

DTC B27A1 is not output.

END (FRONT DOOR OUTSIDE HANDLE ASSEMBLY (FOR DRIVER DOOR) WAS DEFECTIVE)

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

SEE MORE:

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Installation

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Lexus NX: Open in Driver Side Electrical Antenna Circuit (B27A1)

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