DTC B27A5: Open in Front Floor Electrical Key Oscillator Circuit: Procedure

1. Turn the power 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: Go to next step 

1. Disconnect the H1 certification ECU (smart key ECU assembly) connector.
2. Disconnect the H74 No. 1 indoor electrical key antenna assembly (front floor) connector.
3. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   H1-7 (CLG5) - H74-1 (CLG3)	Always	Below 1 Ω
   H1-8 (CG5B) - H74-3 (CLGB)	Always	Below 1 Ω
   H1-15 (E) - Body ground	Always	Below 1 Ω
   H1-7 (CLG5) or H74-1 (CLG3) - Body ground	Always	10 kΩ or higher
   H1-8 (CG5B) or H74-3 (CLGB) - Body ground	Always	10 kΩ or higher

NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

OK: Go to next step 

1. Connect the H1 certification ECU (smart key ECU assembly) connector.
   Fig 1: Identifying H1 Certification ECU (Smart Key ECU Assembly) Connector Terminals And Waveform 1 & 2

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
   TEXT IN ILLUSTRATION
   
   

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

2. Connect the H74 No. 1 indoor electrical key antenna assembly (front floor) connector.
3. Using an oscilloscope, check the waveform.

   OK

   Tester Connection	Switch Condition	Tool Setting	Specified Condition
   H1-7 (CLG5) - H1-15 (E)	Procedure: Power switch off Key not inside vehicle Door is open Door is closed 30 seconds elapse	2 V/DIV., 500 ms/DIV.	Pulse generation (See waveformFigure)
   H1-8 (CG5B) - H1-15 (E)	Procedure: Power switch off Key not inside vehicle Door is open Door is closed 30 seconds elapse	2 V/DIV., 500 ms/DIV.	Pulse generation (See waveformFigure)

NG → See step   7 

OK: Go to next step 

1. Temporarily replace the No. 1 indoor electrical key antenna assembly (front floor) with a new or normally functioning one. Refer to REMOVAL .

NEXT: Go to next step 

1. Clear the DTCs. Refer to DTC CHECK / CLEAR .

NEXT: Go to next step 

1. Check for DTCs. Refer to DTC CHECK / CLEAR .

   OK

   DTC B27A5 is not output.

NG → See step   7 

OK → END (NO. 1 INDOOR ELECTRICAL KEY ANTENNA ASSEMBLY WAS DEFECTIVE)