B1791

SUPPLEMENTAL RESTRAINT SYSTEM: OCCUPANT CLASSIFICATION SYSTEM (for Bench Seat Type): B1791: Collision Detection Signal Line Malfunction
B1791 - Collision Detection Signal Line Malfunction

DESCRIPTION

The center airbag sensor assembly communication circuit consists of the occupant classification ECU and the center airbag sensor assembly.

DTC B1791 is set when a malfunction is detected in the center airbag sensor assembly communication circuit.





HINT
* When DTC B1650/32 is detected as a result of troubleshooting for the supplemental restraint system, check the DTCs stored in the occupant classification ECU, and perform troubleshooting for those DTCs first.
* Use the Techstream to check for DTCs of the occupant classification ECU, otherwise the DTC cannot be read.

WIRING DIAGRAM





INSPECTION PROCEDURE

CAUTION:
In order to prevent unexpected airbag deployment, disconnect the following connectors before inspecting parts such as wire harnesses, if the application of the Techstream probes to the center airbag sensor assembly connector is necessary.

* (a) Turn the ignition switch to the LOCK position.

* (b) Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.

* (c) Disconnect the connectors from the center airbag sensor assembly.

* (d) Disconnect the connectors from the steering pad assembly.

* (e) Disconnect the connector from the front passenger airbag assembly.

* (f) Disconnect the connector from the front seat outer belt assembly LH.

* (g) Disconnect the connector from the front seat outer belt assembly RH.

HINT
Skip the following steps if side and curtain shield airbags are not fitted.

* (h) Disconnect the connector from the front seat side airbag assembly LH.

* (i) Disconnect the connector from the front seat side airbag assembly RH.

* (j) Disconnect the connector from the curtain shield airbag assembly LH.

* (k) Disconnect the connector from the curtain shield airbag assembly RH.

HINT
* If troubleshooting (wire harness inspection) is difficult to perform, remove the front RH seat assembly installation bolts to see the under surface of the seat cushion.
* In the above case, hold the seat so that it does not tip over. Holding the seat up for a long period of time may cause problems, such as seat rail deformation. Hold the seat up only for as long as necessary.

PROCEDURE

1. CHECK DTC

(a) Turn the ignition switch to the ON position.

(b) Clear any DTCs stored in the memory Occupant Classification System (for Bench Seat Type).

HINT
First clear DTCs stored in the occupant classification ECU and then in the center airbag sensor assembly.

(c) Turn the ignition switch to the LOCK position.

(d) Turn the ignition switch to the ON position.

(e) Check the DTCs Occupant Classification System (for Bench Seat Type).

OK:

DTC B1791 is not output.

HINT
DTCs other than B1791 may be output at this time, but they are not related to this check.

OK -- USE SIMULATION METHOD TO CHECK
NG -- Continue to next step.

2. CHECK CONNECTORS

(a) Turn the ignition switch to the LOCK position.

(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 center airbag sensor assembly.

OK:

The connectors are properly connected.

(d) Disconnect the connectors from the occupant classification ECU and center airbag sensor assembly.

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

OK:

The terminals are not deformed or damaged.

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

NG -- REPAIR OR REPLACE WIRE HARNESS OR CONNECTORS
OK -- Continue to next step.

3. CHECK CENTER AIRBAG SENSOR ASSEMBLY COMMUNICATION CIRCUIT (TO B+)

(a) Disconnect the connectors from the occupant classification ECU and center airbag sensor assembly.





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

(c) Turn the ignition switch to the ON position.

(d) Measure the voltage.

Standard voltage:





NG -- CHECK CENTER AIRBAG SENSOR ASSEMBLY COMMUNICATION CIRCUIT (TO B+)
OK -- Continue to next step.

4. CHECK CENTER AIRBAG SENSOR ASSEMBLY COMMUNICATION CIRCUIT (FOR OPEN)

(a) Turn the ignition switch to the LOCK position.





(b) Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.

(c) Measure the resistance.

Standard resistance:





NG -- CHECK CENTER AIRBAG SENSOR ASSEMBLY COMMUNICATION CIRCUIT (FOR OPEN)
OK -- Continue to next step.

5. CHECK CENTER AIRBAG SENSOR ASSEMBLY COMMUNICATION CIRCUIT (TO GROUND)





(a) Measure the resistance.

Standard resistance:





NG -- CHECK CENTER AIRBAG SENSOR ASSEMBLY COMMUNICATION CIRCUIT (TO GROUND)
OK -- Continue to next step.

6. CHECK DTC

(a) Connect the connectors to the occupant classification ECU and the center airbag sensor assembly.

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

(c) Turn the ignition switch to the ON position.

(d) Clear any DTCs stored in the memory Occupant Classification System (for Bench Seat Type).

HINT
First clear DTCs stored in the occupant classification ECU and then in the center airbag sensor assembly.

(e) Turn the ignition switch to the LOCK position.

(f) Turn the ignition switch to the ON position.

(g) Check the DTCs Occupant Classification System (for Bench Seat Type).

OK:

DTC B1791 is not output.

HINT
DTCs other than B1791 may be output at this time, but they are not related to this check.

OK -- USE SIMULATION METHOD TO CHECK
NG -- Continue to next step.

7. REPLACE OCCUPANT CLASSIFICATION ECU

(a) Connect the Techstream to the DLC3.

(b) Turn the ignition switch to the ON position.

(c) Store the occupant classification ECU data into the Techstream Registration.

HINT
If the ECU data cannot be stored in the Techstream, replace the front seat cushion assembly (with occupant classification ECU and occupant classification sensor).

(d) Turn the ignition switch to the LOCK position.

(e) Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.

(f) Replace the occupant classification ECU Removal.

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

(h) Turn the ignition switch to the ON position.

(i) Load the data from the previous ECU stored in the Techstream, into the newly installed ECU Registration.

(j) Turn the ignition switch to the LOCK position.

(k) Turn the ignition switch to the ON position.

(l) Clear the DTCs stored in the memory Occupant Classification System (for Bench Seat Type).

HINT
If DTC is not cleared at this time, past DTC will remain.

NEXT -- Continue to next step.

8. CHECK DTC

(a) Turn the ignition switch to the ON position.

(b) Clear the DTCs stored in the memory Occupant Classification System (for Bench Seat Type).

HINT
First clear DTCs stored in the occupant classification ECU and then in the center airbag sensor assembly.

(c) Turn the ignition switch to the LOCK position.

(d) Turn the ignition switch to the ON position.

(e) Check the DTCs Occupant Classification System (for Bench Seat Type).

OK:

DTC B1791 is not output.

HINT
DTCs other than B1791 may be output at this time, but they are not related to this check.

OK -- PERFORM SENSITIVITY CHECK
NG -- Continue to next step.

9. REPLACE CENTER AIRBAG SENSOR ASSEMBLY

(a) Turn the ignition switch to the LOCK position.

(b) Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.

(c) Replace the center airbag sensor assembly Removal.

NEXT -- Continue to next step.

10. PERFORM SENSITIVITY CHECK

(a) Perform the sensitivity check Initialization.

NEXT -- END

11. CHECK CENTER AIRBAG SENSOR ASSEMBLY COMMUNICATION CIRCUIT (TO B+)

(a) Turn the ignition switch to the LOCK position.





(b) Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.

(c) Disconnect the No. 1 seat wire connector from the floor wire.

(d) Connect the negative (-) terminal cable to the battery and wait for at least 2 seconds.

(e) Turn the ignition switch to the ON position.

(f) Measure the voltage.

Standard voltage:





NG -- CHECK INSTRUMENT PANEL WIRE (TO B+)

OK -- REPLACE NO. 1 SEAT WIRE

12. CHECK CENTER AIRBAG SENSOR ASSEMBLY COMMUNICATION CIRCUIT (FOR OPEN)

(a) Disconnect the No. 1 seat wire connector from the floor wire.





(b) Measure the resistance.

Standard resistance:





NG -- CHECK INSTRUMENT PANEL WIRE (FOR OPEN)

OK -- REPLACE NO. 1 SEAT WIRE

13. CHECK CENTER AIRBAG SENSOR ASSEMBLY COMMUNICATION CIRCUIT (TO GROUND)

(a) Disconnect the No. 1 seat wire connector from the floor wire.





(b) Measure the resistance.

Standard resistance:





NG -- CHECK INSTRUMENT PANEL WIRE (TO GROUND)

OK -- REPLACE NO. 1 SEAT WIRE

14. CHECK INSTRUMENT PANEL WIRE (TO B+)

(a) Turn the ignition switch to the LOCK position.





(b) Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.

(c) Disconnect the floor wire connector from the instrument panel wire.

(d) Connect the negative (-) terminal cable to the battery and wait for at least 2 seconds.

(e) Turn the ignition switch to the ON position.

(f) Measure the voltage.

Standard voltage:





NG -- REPAIR OR REPLACE INSTRUMENT PANEL WIRE

OK -- REPAIR OR REPLACE FLOOR WIRE

15. CHECK INSTRUMENT PANEL WIRE (FOR OPEN)

(a) Disconnect the floor wire connector from the instrument panel wire.





(b) Measure the resistance.

Standard resistance:





NG -- REPAIR OR REPLACE INSTRUMENT PANEL WIRE

OK -- REPAIR OR REPLACE FLOOR WIRE

16. CHECK INSTRUMENT PANEL WIRE (TO GROUND)

(a) Disconnect the floor wire connector from the instrument panel wire.





(b) Measure the resistance.

Standard resistance:





NG -- REPAIR OR REPLACE INSTRUMENT PANEL WIRE

OK -- REPAIR OR REPLACE FLOOR WIRE