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B1790





SUPPLEMENTAL RESTRAINT SYSTEMS: OCCUPANT CLASSIFICATION SYSTEM: B1790: Center Airbag Sensor Assembly Communication Circuit Malfunction
B1790 - Center Airbag Sensor Assembly Communication Circuit Malfunction

DESCRIPTION

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

DTC B1790 is recorded 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 airbag system, check the DTCs stored in the occupant classification ECU. When DTC B1790 is output, perform troubleshooting for the DTC.

WIRING DIAGRAM





INSPECTION PROCEDURE

HINT
* If troubleshooting (wire harness inspection) is difficult to perform, remove the front passenger seat installation bolts to access 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 damage the seat or deform the seat rails. Hold the seat only as necessary.

PROCEDURE

1. CHECK CONNECTORS

(a) Turn the engine switch off.

(b) Disconnect the cable from the negative (-) battery terminal, 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. Also check that the connectors that link the front seat wire RH and floor wire are properly connected.

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 center airbag sensor assembly and the occupant classification ECU. Also disconnect the connectors that link the front seat wire RH and floor wire.

(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 OCCUPANT CLASSIFICATION SYSTEM CIRCUIT (SHORT TO B+)

(a) Connect the connectors that link the front seat wire RH and floor wire.





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

(c) Turn the engine switch on (IG).

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

Standard Voltage:





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

3. CHECK OCCUPANT CLASSIFICATION SYSTEM CIRCUIT (OPEN)

(a) Turn the engine switch off.





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

(c) Using SST, connect terminals 12 (FSP+) and 13 (FSP-) of connector B.

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 FLOOR WIRE (OPEN)
OK -- Continue to next step.

4. CHECK OCCUPANT CLASSIFICATION SYSTEM CIRCUIT (SHORT)

(a) Disconnect SST from connector B.





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

Standard Resistance:





NG -- CHECK FLOOR WIRE (SHORT)
OK -- Continue to next step.

5. CHECK OCCUPANT CLASSIFICATION SYSTEM CIRCUIT (SHORT TO GROUND)

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





Standard Resistance:





NG -- CHECK FLOOR WIRE (SHORT TO GROUND)
OK -- Continue to next step.

6. RECHECK DTC

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

(b) Connect the Techstream to the DLC3.

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

(d) Turn the engine switch on (IG).

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

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

(g) Turn the engine switch off.

(h) Turn the engine switch on (IG).

(i) Using the Techstream, check for DTCs of the occupant classification ECU Reading and Clearing Diagnostic Trouble Codes.

OK:

DTC B1790 is not output.

HINT
Codes other than DTC B1790 may be output at this time, but they are not related to this check.

NG -- REPLACE OCCUPANT CLASSIFICATION ECU

OK -- USE SIMULATION METHOD TO CHECK Diagnosis System

7. REPLACE OCCUPANT CLASSIFICATION ECU

(a) Connect the Techstream to the DLC3.

(b) Turn the engine switch on (IG).

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

(d) Turn the engine 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 engine switch on (IG).

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

(j) Turn the engine switch off.

(k) Turn the engine switch on (IG).

(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.

8. RECHECK DTC

(a) Turn the engine switch on (IG).

(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 assembly DTC Check / Clear.

(d) Turn the engine switch off.

(e) Turn the engine switch on (IG).

(f) Using the Techstream, check for DTCs of the occupant classification ECU Reading and Clearing Diagnostic Trouble Codes.

OK:

DTC B1790 is not output.

HINT
Codes other than DTC B1790 may be output at this time, but they are not related to this check.

NG -- REPLACE CENTER AIRBAG SENSOR ASSEMBLY
OK -- Continue to next step.

9. PERFORM SENSITIVITY CHECK

(a) Perform the sensitivity check Initialization.

NEXT -- END

10. REPLACE CENTER AIRBAG SENSOR ASSEMBLY

(a) Turn the engine switch off.

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

(c) Replace the center airbag sensor assembly Removal.

NEXT -- Continue to next step.

11. PERFORM SENSITIVITY CHECK

(a) Perform the sensitivity check Initialization.

NEXT -- END

12. CHECK FLOOR WIRE (SHORT TO B+)

(a) Turn the engine switch off.





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

(c) Disconnect the front seat wire RH connector from the floor wire.

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

(e) Turn the engine switch on (IG).

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

Standard Voltage:





NG -- REPLACE FLOOR WIRE

OK -- REPLACE FRONT SEAT WIRE RH

13. CHECK FLOOR WIRE (OPEN)

(a) Disconnect the front seat wire RH connector from the floor wire.





HINT
SST has already been inserted into connector B.

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

Standard Resistance:





NG -- REPLACE FLOOR WIRE

OK -- REPLACE FRONT SEAT WIRE RH

14. CHECK FLOOR WIRE (SHORT)

(a) Disconnect the front seat wire RH connector from the floor wire.





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

Standard Resistance:





NG -- REPLACE FLOOR WIRE

OK -- REPLACE FRONT SEAT WIRE RH

15. CHECK FLOOR WIRE (SHORT TO GROUND)

(a) Disconnect the front seat wire RH connector from the floor wire.





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

Standard Resistance:





NG -- REPLACE FLOOR WIRE

OK -- REPLACE FRONT SEAT WIRE RH
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