B1776

SUPPLEMENTAL RESTRAINT SYSTEMS: OCCUPANT CLASSIFICATION SYSTEM: B1773,B1776: Belt Tension Sensor Circuit Malfunction
B1776 - Seat Belt Tension Sensor Power Source Circuit Malfunction

DESCRIPTION

The seat belt tension sensor circuit consists of the occupant classification ECU and the seat belt tension sensor.

The seat belt tension sensor sends the seat belt tension signal to the occupant classification ECU.

DTC B1773 and B1776 are recorded when a malfunction is detected in the seat belt tension sensor circuit.





HINT
When DTC B1650/32 is detected as a result of troubleshooting for the airbag system, check the DTCs stored in the occupant classification ECU. When DTC B1773 and B1776 are output, perform troubleshooting for those DTCs.

WIRING DIAGRAM





INSPECTION PROCEDURE

HINT
- If troubleshooting (wire harness inspection) is difficult to perform, remove the passenger seat installation bolts to access the underside of the seat cushion.
- In the above case, hold the seat so that it does not fall down. Holding the seat for a long period of time may damage the seat or deform the seat rails. Hold the seat only as necessary.

PROCEDURE

1. CHECK CONNECTORS

(a) Turn the ignition switch off.

(b) Disconnect the cable from the negative (-) battery terminal.

(c) Check that the connectors are properly connected to the occupant classification ECU and the seat belt tension sensor.

OK:

The connectors are properly connected.

HINT
If the connectors are not connected securely, reconnect the connectors and proceed to the next inspection.

(d) Disconnect the connectors from the occupant classification ECU and the seat belt tension sensor.

(e) Check that the terminals of the connectors are not damaged.

OK:

The terminals are not deformed or damaged.

NG -- REPLACE WIRE HARNESS
OK -- Continue to next step.

2. CHECK SEAT BELT TENSION SENSOR CIRCUIT (SHORT TO B+)

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





(b) Turn the ignition switch to ON.

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

Standard Voltage:





NG -- CHECK FRONT SEAT WIRE RH (SHORT TO B+)
OK -- Continue to next step.

3. CHECK SEAT BELT TENSION SENSOR CIRCUIT (OPEN)

(a) Turn the ignition switch off.





(b) Disconnect the cable from the negative (-) battery terminal.

(c) Using SST, connect terminals 1 (GBT) and 3 (BT), and connect terminals 2 (VBT) and 3 (BT) of connector E.

NOTICE:
Do not forcibly insert SST into the terminals of the connector when connecting the wire.

SST : 09843-18040

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

Standard Resistance:





NG -- CHECK FRONT SEAT WIRE RH (OPEN)
OK -- Continue to next step.

4. CHECK SEAT BELT TENSION SENSOR CIRCUIT (SHORT TO GROUND)

(a) Disconnect SST from connector E.





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

Standard Resistance:





NG -- CHECK FRONT SEAT WIRE RH (SHORT TO GROUND)
OK -- Continue to next step.

5. CHECK SEAT BELT TENSION SENSOR CIRCUIT (SHORT)

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





Standard Resistance:





NG -- CHECK FRONT SEAT WIRE RH (SHORT)
OK -- Continue to next step.

6. CHECK FOR DTC

(a) Connect the connectors to the occupant classification ECU and the seat belt tension sensor.

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

(c) Turn the ignition switch to ON.

(d) Clear the DTCs stored in the occupant classification ECU Reading and Clearing Diagnostic Trouble Codes.

(e) Clear the DTCs stored in the center airbag sensor assembly DTC Check / Clear.

(f) Turn the ignition switch off.

(g) Turn the ignition switch to ON.

(h) Check for DTCs Reading and Clearing Diagnostic Trouble Codes.

OK:

DTC B1773 and B1776 are not output.

HINT
Codes other than B1773 and B1776 may be output at this time, but they are not related to this check.

NG -- INSPECT FRONT SEAT OUTER BELT ASSEMBLY RH

OK -- USE SIMULATION METHOD TO CHECK Diagnosis System

7. INSPECT FRONT SEAT OUTER BELT ASSEMBLY RH

(a) Turn the ignition switch off.

(b) Disconnect the cable from the negative (-) battery terminal.

(c) Replace the front seat outer belt assembly RH with a known good part Reading and Clearing Diagnostic Trouble Codes.

HINT
Perform an inspection using known good parts from another vehicle if possible.

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

(e) Turn the ignition switch to ON.

(f) Clear the DTCs stored in the occupant classification ECU Reading and Clearing Diagnostic Trouble Codes.

(g) Clear the DTCs stored in the center airbag sensor assembly DTC Check / Clear.

(h) Turn the ignition switch off.

(i) Turn the ignition switch to ON.

(j) Check the DTCs Reading and Clearing Diagnostic Trouble Codes.

OK:

DTC B1773 and B1776 are not output.

HINT
Codes other than B1773 and B1776 may be output at this time, but they are not related to this check.

NG -- REPLACE OCCUPANT CLASSIFICATION ECU

OK -- END

8. REPLACE OCCUPANT CLASSIFICATION ECU

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch to ON.

(c) Using the Techstream, save the ECU data from the ECU currently installed on the vehicle Registration.

(d) Turn the ignition switch off.

(e) Disconnect the cable from the negative (-) battery terminal.

(f) Replace the occupant classification ECU Removal.

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

(h) Turn the ignition switch to ON.

(i) Using the Techstream, load the previous ECU data stored into the new ECU Registration.

(j) Turn the ignition switch off.

(k) Turn the ignition switch to ON.

(l) Clear the DTCs stored in the memory Reading and Clearing Diagnostic Trouble Codes.

HINT
If the DTCs are not cleared at this time, past DTCs will remain.

NEXT -- Continue to next step.

9. PERFORM SENSITIVITY CHECK

(a) Perform the sensitivity check Initialization.

NEXT -- END

10. CHECK FRONT SEAT WIRE RH (SHORT TO B+)

(a) Turn the ignition switch off.





(b) Disconnect the cable from the negative (-) battery terminal.

(c) Disconnect the No. 2 floor wire connector from the front seat wire RH.

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

(e) Turn the ignition switch to ON.

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

Standard Voltage:





NG -- REPLACE FRONT SEAT WIRE RH

OK -- REPLACE NO. 2 FLOOR WIRE

11. CHECK FRONT SEAT WIRE RH (OPEN)

(a) Disconnect the No. 2 floor wire connector from the front seat wire RH.





(b) Using SST, connect terminals 4 (BT) and 8 (GBT), and connect terminals 4 (BT) and 9 (VBT) of connector C.

NOTICE:
Do not forcibly insert SST into the terminals of the connector when connecting the wire.

SST : 09843-18040

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

Standard Resistance:





NG -- REPLACE FRONT SEAT WIRE RH

OK -- REPLACE NO. 2 FLOOR WIRE

12. CHECK FRONT SEAT WIRE RH (SHORT TO GROUND)

(a) Disconnect the No. 2 floor wire connector from the front seat wire RH.





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

Standard Resistance:





NG -- REPLACE FRONT SEAT WIRE RH

OK -- REPLACE NO. 2 FLOOR WIRE

13. CHECK FRONT SEAT WIRE RH (SHORT)

(a) Disconnect the No. 2 floor wire connector from the front seat wire RH.





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

Standard Resistance:





NG -- REPLACE FRONT SEAT WIRE RH

OK -- REPLACE NO. 2 FLOOR WIRE