DTC B1771: Passenger Side Buckle Switch Circuit Malfunction: Procedure

CHECK CONNECTORS
1. Turn the power switch off.
2. Disconnect the cable from the negative (-) auxiliary battery terminal.
3. Check that the connectors are properly connected to the occupant detection ECU and front seat inner belt assembly RH.
  OK
  
  The connectors are properly connected.
  
  HINT:
  
  If the connectors are not connected securely, reconnect the connectors and proceed to the next inspection.
4. Disconnect the connectors from the occupant detection ECU and front seat inner belt assembly RH.
5. Check that the terminals of the connectors are not damaged.
  OK
  
  The terminals are not deformed or damaged.
NG → REPLACE FRONT SEAT WIRE RH

OK: Go to next step

CHECK FRONT SEAT WIRE RH (SHORT TO B+)

Connect the cable to the negative (-) auxiliary battery terminal.

Fig 1: Identifying W4 Connector Terminals
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
Turn the power switch on (IG).

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

Standard Voltage

Tester Connection	Switch Condition	Specified Condition
W4-9 (BSW) - Body ground	Power switch on (IG)	Below 1 V
W4-5 (BGND) - Body ground	Power switch on (IG)	Below 1 V

TEXT IN ILLUSTRATION

*1	Front Seat Inner Belt Assembly RH
*2	Occupant Detection ECU
*3	Front Seat Wire RH
*4	Connector B
*a	Front view of wire harness connector (to Occupant Detection ECU)

NG → REPLACE FRONT SEAT WIRE RH

OK: Go to next step

CHECK FRONT SEAT WIRE RH (OPEN)

Turn the power switch off.

Fig 2: Identifying W4 And W5 Connector Terminals
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
Disconnect the cable from the negative (-) auxiliary battery terminal.
Using SST, connect terminals 1 (BSW) and 2 (BGND) of connector C.
NOTE:
Do not forcibly insert SST into the terminals of the connector when connecting.
- SST: 09843-18040

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

Standard Resistance

Tester Connection	Condition	Specified Condition
W4-9 (BSW) - W4-5 (BGND)	Always	Below 1 Ω

TEXT IN ILLUSTRATION

*1	Front Seat Inner Belt Assembly RH	*2	Occupant Detection ECU
*3	Front Seat Wire RH	*4	Connector B
*5	Connector C	-	-
*a	Front view of wire harness connector (to Occupant Detection ECU)	*b	Front view of wire harness connector (to Front Seat Inner Belt Assembly RH)

NG → REPLACE FRONT SEAT WIRE RH

OK: Go to next step

CHECK FRONT SEAT WIRE RH (SHORT)

Disconnect SST from connector C.

Fig 3: Identifying W4 Connector Terminals
Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

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

Standard Resistance

Tester Connection	Condition	Specified Condition
W4-9 (BSW) - W4-5 (BGND)	Always	1 MΩ or higher

TEXT IN ILLUSTRATION

*1	Front Seat Inner Belt Assembly RH
*2	Occupant Detection ECU
*3	Front Seat Wire RH
*4	Connector B
*a	Front view of wire harness connector (to Occupant Detection ECU)

NG → REPLACE FRONT SEAT WIRE RH

OK: Go to next step

CHECK FRONT SEAT WIRE RH (SHORT TO GROUND)

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

Fig 4: Identifying W4 Connector Terminals

Standard Resistance

Tester Connection	Condition	Specified Condition
W4-9 (BSW) - Body ground	Always	1 MΩ or higher
W4-5 (BGND) - Body ground	Always	1 MΩ or higher

TEXT IN ILLUSTRATION

*1	Front Seat Inner Belt Assembly RH
*2	Occupant Detection ECU
*3	Front Seat Wire RH
*4	Connector B
*a	Front view of wire harness connector (to Occupant Detection ECU)

NG → REPLACE FRONT SEAT WIRE RH

OK: Go to next step

CHECK DTC
1. Connect the connectors to the occupant detection ECU and front seat inner belt assembly RH.
2. Connect the cable to the negative (-) auxiliary battery terminal.
3. Turn the power switch on (IG).
4. Clear the DTCs stored in the occupant detection ECU. Refer to DTC CHECK / CLEAR [08/2012 - ] .
5. Clear the DTCs stored in the airbag sensor assembly. Refer to DTC CHECK / CLEAR [08/2012 - ] .
6. Turn the power switch off.
7. Turn the power switch on (IG).
8. Check for DTCs. Refer to DTC CHECK / CLEAR [08/2012 - ] .
  OK
  
  DTC B1771 is not output.
  
  HINT:
  
  Codes other than DTC B1771 may be output at this time, but they are not related to this check.
NG → See step 7

OK → See step 11
CHECK FRONT SEAT INNER BELT ASSEMBLY RH
1. Turn the power switch off.
2. Disconnect the cable from the negative (-) auxiliary battery terminal.
3. Replace the front seat inner belt assembly RH with a known good one. Refer to REMOVAL [08/2012 - ] for Manual seat. Refer to REMOVAL [08/2012 - ] for Power seat).
  HINT:
  
  Perform the following inspection using known good parts from another vehicle if possible.
4. Connect the cable to the negative (-) auxiliary battery terminal.
5. Turn the power switch on (IG).
6. Clear the DTCs stored in the occupant detection ECU. Refer to DTC CHECK / CLEAR [08/2012 - ] .
7. Clear the DTCs stored in the airbag sensor assembly. Refer to DTC CHECK / CLEAR [08/2012 - ] .
8. Turn the power switch off.
9. Turn the power switch on (IG).
10. Check for DTCs. Refer to DTC CHECK / CLEAR [08/2012 - ] .
  OK
  
  DTC B1771 is not output.
  
  HINT:
  
  Codes other than DTC B1771 may be output at this time, but they are not related to this check.
NG → See step 8

OK → END
REPLACE OCCUPANT DETECTION ECU
1. Turn the power switch off.
2. Disconnect the cable from the negative (-) auxiliary battery terminal.
3. Replace the occupant detection ECU. Refer to REMOVAL [08/2012 - ] .
NEXT: Go to next step
PERFORM ZERO POINT CALIBRATION
1. Connect the cable to the negative (-) auxiliary battery terminal.
2. Turn the power switch on (IG).
3. Using the Techstream, perform Zero Point Calibration. Refer to INITIALIZATION [08/2012 - ] .
NEXT: Go to next step
PERFORM SENSITIVITY CHECK
1. Using the Techstream, perform Sensitivity Check. Refer to INITIALIZATION [08/2012 - ] .
NEXT → END
USE SIMULATION METHOD TO CHECK. Refer to HOW TO PROCEED WITH TROUBLESHOOTING [08/2012 - ]