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 certification ECU (smart key ECU assembly) to detect when the key is inside the vehicle, the signal from the certification ECU (smart key ECU assembly) requesting a response from the key 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.	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*1).	Harness or connector Electrical key wire harness No. 1 Indoor electrical key antenna assembly (front floor) Certification ECU (smart key ECU assembly)	Any time*2

*1: Only output while a malfunction is present.
*2: Only when the vehicle is stopped.

Vehicle Condition and Fail-safe Operation when Malfunction Detected
Vehicle Condition when Malfunction Detected	Fail-safe Operation when Malfunction Detected
When key is in front seat area: Power source mode does not change when power switch pressed Key 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

Note

When using the GTS with the vehicle power switch off, connect the GTS to the vehicle 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 the 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.
The push-button start system uses multiplex communication. First perform the inspections in "How to Proceed with Troubleshooting" to confirm that there are no communication malfunctions before proceeding with troubleshooting Click here.
Before replacing the certification ECU (smart key ECU assembly), refer to the push-button start system precaution Click here.
After repair, confirm DTC does not reoccur by performing the "DTC Output Confirmation Operation".
No. 1 indoor electrical key antenna assembly (front floor) has an antenna coil between ANTE5 and CLGB terminals.

PROCEDURE

CHECK CONNECTOR CONNECTION CONDITION
1. Turn the power switch off.
2. Check that the connectors are properly connected to the certification ECU (smart key ECU assembly) and the No. 1 indoor electrical key antenna assembly (front floor).
  
  OK
  
  Connectors are properly connected.
NG
CONNECT CONNECTORS PROPERLY

OK

OK
Connectors are properly connected.

INSPECT ELECTRICAL KEY WIRE HARNESS

Remove the electrical key wire harness.

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

Standard Resistance

for LHD
Tester Connection	Condition	Specified Condition
FF2-5 - FF2-1	Always	Below 1 Ω
FF2-4 - FF2-2	Always	Below 1 Ω

for RHD
Tester Connection	Condition	Specified Condition
FF1-5 - FF1-1	Always	Below 1 Ω
FF1-4 - FF1-2	Always	Below 1 Ω

Reinstall the electrical key wire harness.

REPLACE ELECTRICAL KEY WIRE HARNESS

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

Disconnect the F86 and F88 certification ECU (smart key ECU assembly) connectors.
Disconnect the F45 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
F86-3 (CLG5) - F45-1 (ANTE5)	Always	Below 1 Ω
F86-2 (CG5B) - F45-2 (CLGB)	Always	Below 1 Ω
F88-11 (E) - Body ground	Always	Below 1 Ω
F86-3 (CLG5) - Body ground	Always	10 kΩ or higher
F86-2 (CG5B) - Body ground	Always	10 kΩ or higher

REPAIR OR REPLACE HARNESS OR CONNECTOR

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

Text in Illustration
*a	Component with harness connected (Certification ECU (smart key ECU assembly))	*b	Waveform
*c	Door open	*d	After approximately 30 seconds from when the door is closed

Reconnect the F86 and F88 certification ECU (smart key ECU assembly) connectors.
Reconnect the F45 No. 1 indoor electrical key antenna assembly (front floor) connector.

Using an oscilloscope, check the waveform.

Tech Tips

Check that the entry cancel function, which is one of the customizing settings of the push-button start system, is not set Click here.

Tester Connection

Switch Condition

Tool Setting

Specified Condition

F86-3 (CLG5) - F88-11 (E)

Procedure:

Power 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)

F86-2 (CG5B) - F88-11 (E)

Procedure:

Power 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 normally functioning one Click here.
NEXT
CHECK DTC OUTPUT
1. Clear the DTCs Click here.
2. Recheck for DTCs Click here.
  
  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)