Lexus NX manuals

Lexus NX: Open in Front Floor Electrical Key Oscillator Circuit (B27A5)

Lexus NX Service Manual / Vehicle Interior / Theft Deterrent / Keyless Entry / Smart Access System With Push-button Start (for Entry Function) / Open in Front Floor Electrical Key Oscillator Circuit (B27A5)

DESCRIPTION

The certification ECU (smart key ECU assembly) generates a request signal and transmits the signal to the No. 1 indoor electrical key antenna assembly (front floor). For the No. 1 indoor electrical key antenna assembly (front floor) to detect when the electrical key transmitter sub-assembly is in the cabin, the signal from the certification ECU (smart key ECU assembly) requesting a response from the electrical key transmitter sub-assembly is transmitted inside the vehicle. DTC B27A5 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 No. 1 indoor electrical key antenna assembly (front floor) (between terminals CLG5 and ANTE5, or terminals CG5B and CLGB).

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

Note

B27A5

Open in Front Floor Electrical Key Oscillator Circuit

An open circuit is detected in the circuit between the certification ECU (smart key ECU assembly) and No. 1 indoor electrical key antenna assembly (front floor) (CLG5 - ANTE5, CG5B - CLGB) (1 trip detection logic*).
  • Certification ECU (smart key ECU assembly)
  • No. 1 indoor electrical key antenna assembly (front floor)
  • 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

When electrical key transmitter sub-assembly is in front seat area:

  • Power source mode does not change when power switch pressed
  • Electrical key transmitter sub-assembly locked inside vehicle

-
Related Data List and Active Test

DTC No.

Data List and Active Test

B27A5

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.

    Click here

  • 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.

    Click here

  • 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 No. 1 indoor electrical key antenna assembly (front floor).

OK:

Connectors are properly connected.

NG

CONNECT CONNECTORS PROPERLY
OK

2.

CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) - NO. 1 INDOOR ELECTRICAL KEY ANTENNA ASSEMBLY (FRONT FLOOR))

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

(b) Disconnect the I27 No. 1 indoor electrical key antenna assembly (front floor) connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

I53-21 (CLG5) - I27-1 (ANTE5)

Always

Below 1 Ω

I53-20 (CG5B) - I27-3 (CLGB)

Always

Below 1 Ω

I53-11 (E) - Body ground

Always

Below 1 Ω

I53-21 (CLG5) or I27-1 (ANTE5) - Body ground

Always

10 kΩ or higher

I53-20 (CG5B) or I27-3 (CLGB) - Body ground

Always

10 kΩ or higher

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

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

3.

CHECK CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) (OUTPUT TO NO. 1 INDOOR ELECTRICAL KEY ANTENNA ASSEMBLY (FRONT FLOOR))

*a

Component with harness connected

(Certification ECU (Smart Key ECU Assembly))

*b

Waveform 1

*c

For 30 seconds after closing any door using the door outside handle

*d

30 seconds or more have elapsed after closing any door using the door outside handle

(a) Using an oscilloscope, check the waveform.

OK:

Tester Connection

Condition

Tool Setting

Specified Condition

I53-21 (CLG5) - I53-11 (E)

Procedure:

  1. Power switch off
  2. Electrical key transmitter sub-assembly not inside vehicle
  3. Within 30 seconds of closing any door using the door outside handle

2 V/DIV., 500 ms/DIV.

Pulse generation

(See waveform 1)

I53-20 (CG5B) - I53-11 (E)

Procedure:

  1. Power switch off
  2. Electrical key transmitter sub-assembly not inside vehicle
  3. Within 30 seconds of closing any door using the door outside handle

2 V/DIV., 500 ms/DIV.

Pulse generation

(See waveform 1)
NG

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

OK

4.

REPLACE NO. 1 INDOOR ELECTRICAL KEY ANTENNA ASSEMBLY (FRONT FLOOR)

(a) Temporarily replace the No. 1 indoor electrical key antenna assembly (front floor) with a new one.

Click here

NEXT

5.

CLEAR DTC

(a) Clear the DTCs.

Body Electrical > Smart Access > Clear DTCs
NEXT

6.

CHECK FOR DTC

(a) Check for DTCs.

Body Electrical > Smart Access > Trouble Codes

OK:

DTC B27A5 is not output.

OK

END (NO. 1 INDOOR ELECTRICAL KEY ANTENNA ASSEMBLY (FRONT FLOOR) WAS DEFECTIVE)
NG

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

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