PUSH-BUTTON START, Diagnostic DTC:B27A5

DTC Code	DTC Name
B27A5	Open in Front Floor Electrical Key Oscillator Circuit

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 inside the vehicle, 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 Code	DTC Detection Condition	Trouble Area	DTC Output Confirmation Operation
B27A5	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*).	Harness or connector No. 1 indoor electrical key antenna assembly (front floor) Certification ECU (smart key ECU assembly)	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 engine switch pressed Electrical key transmitter sub-assembly locked inside vehicle	-

Related Data List and Active Test
DTC Code	Data List and Active Test
B27A5	Key diagnostic mode can be used to perform troubleshooting

WIRING DIAGRAM

INSPECTION PROCEDURE

Note

The push-button start uses a multiplex communication system (LIN communication system and the CAN communication system). Inspect the communication function by following How to Proceed with Troubleshooting Click here. Troubleshoot the push-button start after confirming that the communication systems are functioning properly.
When using the GTS with the engine switch off, connect the GTS to the DLC3 and turn a courtesy light switch on and off at intervals of 1.5 seconds or less until communication between the GTS and the vehicle begins. Then select Model Code "KEY REGIST" under manual mode and enter the following menus: Body Electrical /Entry&Start(CAN). While using the GTS, periodically turn a courtesy light switch on and off at intervals of 1.5 seconds or less to maintain communication between the GTS and the vehicle.
Before replacing the certification ECU (smart key ECU assembly), refer to the push-button start precaution Click here.
After repair, confirm that no DTCs are output by performing the "DTC Output Confirmation Operation".
The No. 1 indoor electrical key antenna assembly (front floor) has an antenna coil between ANTE5 and CLGB terminals.

PROCEDURE

CHECK CONNECTOR CONNECTION
1. Turn the engine switch off.
2. 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

OK
Connectors are properly connected.

CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU - NO. 1 INDOOR ELECTRICAL KEY ANTENNA ASSEMBLY AND BODY GROUND)

Disconnect the A34 and N93 certification ECU (smart key ECU assembly) connectors.
Disconnect the N53 No. 1 indoor electrical key antenna assembly (front floor) connector.

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

Standard Resistance

Tester Connection	Condition	Specified Condition
N93-3 (CLG5) - N53-1 (ANTE5)	Always	Below 1 Ω
N93-2 (CG5B) - N53-3 (CLGB)	Always	Below 1 Ω
A34-11 (E) - Body ground	Always	Below 1 Ω
N93-3 (CLG5) or N53-1 (ANTE5) - Body ground	Always	10 kΩ or higher
N93-2 (CG5B) or N53-3 (CLGB) - Body ground	Always	10 kΩ or higher

REPAIR OR REPLACE HARNESS OR CONNECTOR

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

Connect the A34 and N93 certification ECU (smart key ECU assembly) connectors.

Text in Illustration
*1	Waveform	-	-
*a	Component with harness connected (Certification ECU (Smart Key ECU Assembly))	*b	Within approximately 30 seconds from when the door is closed
*c	After approximately 30 seconds from when the door is closed	-	-

Connect the N53 No. 1 indoor electrical key antenna assembly (front floor) connector.

Using an oscilloscope, check the waveform.

Tester Connection

Switch Condition

Tool Setting

Specified Condition

N93-3 (CLG5) - A34-11 (E)

Procedure:

Engine switch off
Electrical key transmitter sub-assembly not inside vehicle
Door is open
Door is closed
Within 30 seconds

2 V/DIV., 500 ms/DIV.

Pulse generation (See waveform)

N93-2 (CG5B) - A34-11 (E)

Procedure:

Engine switch off
Electrical key transmitter sub-assembly not inside vehicle
Door is open
Door is closed
Within 30 seconds

2 V/DIV., 500 ms/DIV.

Pulse generation (See waveform)

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

REPLACE NO. 1 INDOOR ELECTRICAL KEY ANTENNA ASSEMBLY (FRONT FLOOR)
1. Temporarily replace the No. 1 indoor electrical key antenna assembly (front floor) with a new or known good one Click here.
NEXT
CLEAR DTC
1. Clear the DTCs Click here.
NEXT
CHECK FOR DTC
1. Check for DTCs Click here.
  
  OK
  
  DTC B27A5 is not output.
NG
REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

OK

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