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 airbag sensor assembly communication circuit consists of the occupant detection ECU and airbag sensor assembly.

DTC B1790 is stored when a malfunction is detected in the 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 detection ECU. When DTC B1790 is output, perform troubleshooting for the DTC.

WIRING DIAGRAM





INSPECTION PROCEDURE

NOTICE:
After turning the power switch off, waiting time may be required before disconnecting the cable from the negative (-) auxiliary battery terminal. Therefore, make sure to read the disconnecting the cable from the negative (-) auxiliary battery terminal notices before proceeding with work Service Precautions.

HINT
* If troubleshooting (wire harness inspection) is difficult to perform, remove the front passenger seat installation bolts to see under the seat cushion.
* In the above case, lift and hold the seat so that it does not fall down. Hold the seat only as necessary because holding the seat for a long period of time may cause seat rail deformation.

PROCEDURE

1. CHECK CONNECTORS

(a) Turn the power switch off.

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

CAUTION:
Wait at least 90 seconds after disconnecting the cable from the negative (-) auxiliary battery terminal to disable the SRS system.

(c) Check that the connectors are properly connected to the airbag sensor assembly and occupant detection ECU. Also check that the connectors that link the front seat wire RH and No. 2 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 airbag sensor assembly and occupant detection ECU. Also disconnect the connectors that link the front seat wire RH and No. 2 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 cable to the negative (-) auxiliary battery terminal.





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

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

Standard Voltage:





Text in Illustration





NG -- CHECK NO. 2 FLOOR WIRE (SHORT TO B+)
OK -- Continue to next step.

3. CHECK OCCUPANT CLASSIFICATION SYSTEM CIRCUIT (OPEN)

(a) Turn the power switch off.





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

CAUTION:
Wait at least 90 seconds after disconnecting the cable from the negative (-) auxiliary battery terminal to disable the SRS system.

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

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

SST : 09843-18040

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

Standard Resistance:





Text in Illustration





NG -- CHECK NO. 2 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:





Text in Illustration





NG -- CHECK NO. 2 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:





Text in Illustration





NG -- CHECK NO. 2 FLOOR WIRE (SHORT TO GROUND)
OK -- Continue to next step.

6. CHECK DTC

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

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

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

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

(e) Clear the DTCs stored in the airbag sensor assembly Reading and Clearing Diagnostic Trouble Codes.

(f) Turn the power switch off.

(g) Turn the power switch on (IG).

(h) Check for DTCs 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 DETECTION ECU

OK -- USE SIMULATION METHOD TO CHECK How To Proceed With Troubleshooting

7. REPLACE OCCUPANT DETECTION ECU

(a) Turn the power switch off.

(b) Disconnect the cable from the negative (-) auxiliary battery terminals.

CAUTION:
Wait at least 90 seconds after disconnecting the cable from the negative (-) auxiliary battery terminal to disable the SRS system.

(c) Replace the occupant detection ECU with a known good one Removal.

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

NEXT -- Continue to next step.

8. RECHECK DTC

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

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

(c) Clear the DTCs stored in the airbag sensor assembly Reading and Clearing Diagnostic Trouble Codes.

(d) Turn the power switch off.

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

(f) Check for DTCs 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 AIRBAG SENSOR ASSEMBLY Removal
OK -- Continue to next step.

9. PERFORM ZERO POINT CALIBRATION

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

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

(c) Using the Techstream, perform Zero Point Calibration Programming and Relearning.

NEXT -- Continue to next step.

10. PERFORM SENSITIVITY CHECK

(a) Using the Techstream, perform Sensitivity Check Programming and Relearning.

NEXT -- END

11. CHECK NO. 2 FLOOR WIRE (SHORT TO B+)

(a) Turn the power switch off.





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

CAUTION:
Wait at least 90 seconds after disconnecting the cable from the negative (-) auxiliary battery terminal to disable the SRS system.

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

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

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

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

Standard Voltage:





Text in Illustration





NG -- REPLACE NO. 2 FLOOR WIRE

OK -- REPLACE FRONT SEAT WIRE RH

12. CHECK NO. 2 FLOOR WIRE (OPEN)

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





Text in Illustration





NG -- REPLACE NO. 2 FLOOR WIRE

OK -- REPLACE FRONT SEAT WIRE RH

13. CHECK NO. 2 FLOOR WIRE (SHORT)

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





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

Standard Resistance:





Text in Illustration





NG -- REPLACE NO. 2 FLOOR WIRE

OK -- REPLACE FRONT SEAT WIRE RH

14. CHECK NO. 2 FLOOR WIRE (SHORT TO GROUND)

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





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

Standard Resistance:





Text in Illustration





NG -- REPLACE NO. 2 FLOOR WIRE

OK -- REPLACE FRONT SEAT WIRE RH