B1776

SUPPLEMENTAL RESTRAINT SYSTEM: OCCUPANT CLASSIFICATION SYSTEM:

DTC B1773 - Belt Tension Sensor Circuit Malfunction

DTC 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.
DTCs 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 DTCs B1773 and B1776 are output, perform troubleshooting for the DTCs.

WIRING DIAGRAM

INSPECTION PROCEDURE
HINT:
- If troubleshooting (wire harness inspection) is difficult to perform, remove the passenger seat installation bolts to see the undersurface 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 cause a problem, such as seat rail deformation. Hold the seat only as necessary.

PROCEDURE

1. CHECK FOR DTC
(a) Turn the ignition switch to ON.
(b) Clear the DTCs stored in the occupant classification ECU Reading and Clearing Diagnostic Trouble Codes.
(c) Clear the DTCs stored in the center airbag sensor DTC Check / Clear.
(d) Turn the ignition switch to OFF.
(e) Turn the ignition switch to ON.
(f) Check for the DTCs Reading and Clearing Diagnostic Trouble Codes.
OK:
DTCs B1773 and B1776 are not output.
HINT: Codes other than DTCs B1773 and B1776 may be output at this time, but they are not related to this check.

NG -- CHECK CONNECTION OF CONNECTOR
OK -- USE SIMULATION METHOD TO CHECK
2. CHECK CONNECTION OF CONNECTOR
(a) Turn the ignition switch to OFF.
(b) Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.
(c) Check that the connectors are properly connected to the occupant classification ECU and the seat belt tension sensor.
OK:
Connectors are properly connected.
NG -- CONNECT CONNECTORS PROPERLY
OK -- Continue to next step.
3. CHECK CONNECTOR
(a) Disconnect the connectors from the occupant classification ECU and the belt tension sensor.
(b) Check that the connectors (on the occupant classification ECU side and seat belt tension sensor side) are not damaged.
OK:
Connectors are not deformed or damaged.
HINT: If the connectors are not connected securely, reconnect the connectors and proceed to the next inspection.

NG -- REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.
4. CHECK SEAT BELT TENSION SENSOR CIRCUIT

(a) Connect the negative (-) terminal cable to the battery.
(b) Turn the ignition switch to ON.
(c) Measure the voltage according to the value(s) in the table below.
Standard voltage:

(d) Turn the ignition switch to OFF.
(e) Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.
(f) Using 2 service wires, connect terminals 3 (BT) and 1 (GBT), and connect terminals 2 (VBT) and 1 (GBT) of connector E.
NOTICE: Do not forcibly insert the service wires into the terminals of the connector when connecting the wire.
(g) Measure the resistance according to the value(s) in the table below.
Standard resistance:

(h) Disconnect the service wires from connector E.
(i) Measure the resistance according to the value(s) in the table below.
Standard resistance:

NG -- CHECK NO. 2 FLOOR WIRE
OK -- Continue to next step.
5. CHECK FOR DTC
(a) Connect the connectors to the occupant classification ECU and the seat belt tension sensor.
(b) Connect the negative (-) terminal cable to the battery.
(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 DTC Check / Clear.
(f) Turn the ignition switch to OFF.
(g) Turn the ignition switch to ON.
(h) Check for the DTCs Reading and Clearing Diagnostic Trouble Codes.
OK:
DTCs B1773 and B1776 are not output.
HINT: Codes other than DTCs B1773 and B1776 may be output at this time, but they are not related to this check.

NG -- REPLACE FRONT SEAT OUTER BELT ASSEMBLY RH (SEAT BELT TENSION SENSOR)
OK -- USE SIMULATION METHOD TO CHECK
6. REPLACE FRONT SEAT OUTER BELT ASSEMBLY RH (SEAT BELT TENSION SENSOR)
(a) Turn the ignition switch to OFF.
(b) Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.
(c) Replace the front seat outer belt Removal.
HINT: Perform the inspection using parts from a normal vehicle if possible.
(d) Connect the negative (-) terminal cable to the battery.
NEXT -- Continue to next step.
7. CHECK FOR DTC
(a) Turn the ignition switch to ON.
(b) Clear the DTCs stored in the occupant classification ECU Reading and Clearing Diagnostic Trouble Codes.
(c) Clear the DTCs stored in the center airbag sensor DTC Check / Clear.
(d) Turn the ignition switch to OFF.
(e) Turn the ignition switch to ON.
(f) Check for the DTCs Reading and Clearing Diagnostic Trouble Codes.
OK:
DTCs B1773 and B1776 are not output.
HINT: Codes other than DTCs B1773 and B1776 may be output at this time, but they are not related to this check.

NG -- PERFORM REGISTRATION BEFORE ECU EXCHANGE
OK -- END
8. PERFORM REGISTRATION BEFORE ECU EXCHANGE
(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 which was installed on the vehicle Registration.
NEXT -- Continue to next step.
9. REPLACE OCCUPANT CLASSIFICATION ECU
(a) Turn the ignition switch to OFF.
(b) Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.
(c) Replace the occupant classification ECU Removal.
(d) Connect the negative (-) terminal cable to the battery.
NEXT -- Continue to next step.
10. PERFORM REGISTRATION AFTER ECU EXCHANGE
(a) Turn the ignition switch to ON.
(b) Using the Techstream, load the previous ECU data stored in the tester into the new ECU Registration.
NEXT -- Continue to next step.
11. PERFORM ZERO POINT CALIBRATION
(a) Using the Techstream, perform zero point calibration Initialization.
NEXT -- Continue to next step.
12. CHECK FOR DTC
HINT: Check that the zero point calibration is completed normally. If one of the following conditions is met, DTC B1797 will be output (refer to INITIALIZATION Initialization):
- Zero point calibration is performed when the conditions for the calibration are not satisfied.
- Zero point calibration has failed.
(a) Clear the DTCs stored in the occupant classification ECU Reading and Clearing Diagnostic Trouble Codes.
(b) Clear the DTCs stored in the center airbag sensor DTC Check / Clear.
(c) Turn the ignition switch to OFF.
(d) Turn the ignition switch to ON.
(e) Check for the DTCs Reading and Clearing Diagnostic Trouble Codes.
OK:
DTC B1797 is not output.
NG -- GO TO DTC B1797
OK -- Continue to next step.
13. PERFORM SENSITIVITY CHECK
(a) Perform the sensitivity check Initialization.
NEXT -- END
14. CHECK NO. 2 FLOOR WIRE

(a) Disconnect the front seat wire RH connector from the No. 2 floor wire.
(b) Connect the negative (-) terminal cable to the battery.
(c) Turn the ignition switch to ON.
(d) Measure the voltage according to the value(s) in the table below.
Standard voltage:

(e) Turn the ignition switch to OFF.
(f) Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.
(g) Using 2 service wires, connect terminals 3 (BT) and 1 (GBT), and connect terminals 2 (VBT) and 1 (GBT) of connector E.
NOTICE: Do not forcibly insert the service wires into the terminals of the connector when connecting the wire.
(h) Measure the resistance according to the value(s) in the table below.
Standard resistance:

(i) Disconnect the service wires from connector E.
(j) Measure the resistance according to the value(s) in the table below.
Standard resistance:

NG -- REPLACE NO. 2 FLOOR WIRE
OK -- REPLACE FRONT SEAT WIRE RH