B1790

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

DTC B1790 - Center Airbag Sensor Assembly Communication Circuit Malfunction

DESCRIPTION

The center airbag sensor communication circuit consists of the occupant classification ECU and the center airbag sensor.
DTC B1790 is recorded when a malfunction is detected in the center airbag sensor communication circuit.






WIRING DIAGRAM





INSPECTION PROCEDURE
HINT:
- If troubleshooting (wire harness inspection) is difficult to perform, remove the front passenger seat installation bolts to see the undersurface of the seat cushion.
- In the above case, hold the seat so that it does not tip over. Holding the seat for a long period of time may cause a problem, such as seat rail deformation. Hold the seat up only for as long as necessary.

PROCEDURE

1. CHECK FOR DTC
(a) Turn the power switch ON (IG).
(b) Clear the DTCs Reading and Clearing Diagnostic Trouble Codes.
HINT: First clear DTCs stored in the occupant classification ECU and then in the center airbag sensor.
(c) Turn the power switch OFF.
(d) Turn the power switch ON (IG).
(e) Check the DTCs Reading and Clearing Diagnostic Trouble Codes.
OK:
DTC B1790 is not output.
HINT: DTCs other than DTC B1790 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 CONNECTION OF CONNECTOR
(a) Turn the power 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.
OK:
The connectors are properly connected.
NG -- CONNECT CONNECTOR
OK -- Continue to next step.

3. CHECK FLOOR WIRE NO. 2 (TO B+)




(a) Disconnect the connectors from the occupant classification ECU and the center airbag sensor.
(b) Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.
(c) Turn the power switch ON (IG).
(d) Measure the voltage of the wire harness side connector.
Standard voltage:






NG -- REPAIR OR REPLACE FLOOR WIRE NO. 2
OK -- Continue to next step.

4. CHECK FLOOR WIRE NO. 2 (OPEN)




(a) Turn the power switch OFF.
(b) Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
(c) Using a service wire, connect terminals A19-16 (FSP+) and A19-24 (FSP-) of connector B.
NOTE: Do not forcibly insert a service wire into the terminals of the connector when connecting them.
(d) Measure the resistance of the wire harness side connector.
Standard resistance:






NG -- REPAIR OR REPLACE FLOOR WIRE NO. 2
OK -- Continue to next step.

5. CHECK FLOOR WIRE NO. 2 (SHORT)




(a) Disconnect the service wire from connector B.
(b) Measure the resistance of the wire harness side connector.
Standard resistance:






NG -- REPAIR OR REPLACE FLOOR WIRE NO. 2
OK -- Continue to next step.

6. CHECK FLOOR WIRE NO. 2 (TO GROUND)




(a) Measure the resistance of the wire harness side connector.
Standard resistance:






NG -- REPAIR OR REPLACE FLOOR WIRE NO. 2
OK -- Continue to next step.

7. CHECK FOR DTC
(a) Connect the connectors to the occupant classification ECU and the center airbag sensor.
(b) Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.
(c) Turn the power switch ON (IG).
(d) Clear the DTCs Reading and Clearing Diagnostic Trouble Codes.
HINT: First clear DTCs stored in the occupant classification ECU and then in the center airbag sensor.
(e) Turn the power switch OFF.
(f) Turn the power switch ON (IG).
(g) Check the DTCs Reading and Clearing Diagnostic Trouble Codes.
OK:
DTC B1790 is not output.
HINT: DTCs other than DTC B1790 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.

8. REPLACE OCCUPANT CLASSIFICATION ECU
(a) Turn the power switch OFF.
(b) Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
(c) Replace the occupant classification ECU.
HINT: Perform the inspection using parts from a normal vehicle if possible.

NEXT -- Continue to next step.

9. PERFORM ZERO POINT CALIBRATION
(a) Connect the cable to the negative (-) terminal battery, and wait for at least 2 seconds.
(b) Connect the Techstream to the DLC3.
(c) Turn the power switch ON (IG).
(d) Using the Techstream, perform the zero point calibration Programming and Relearning.
OK:
"Zero Point Calibration is complete." is displayed.
NEXT -- Continue to next step.

10. PERFORM SENSITIVITY CHECK
(a) Using the Techstream, perform the sensitivity check Programming and Relearning.
Standard values:
27 to 33 kg (59.52 to 72.75 lb)
NEXT -- Continue to next step.

11. CHECK FOR DTC
(a) Turn the power switch ON (IG).
(b) Clear the DTCs Reading and Clearing Diagnostic Trouble Codes.
HINT: First clear DTCs stored in the occupant classification ECU and then in the center airbag sensor.
(c) Turn the power switch OFF.
(d) Turn the power switch ON (IG).
(e) Check the DTCs Reading and Clearing Diagnostic Trouble Codes.
OK:
DTC B1790 is not output.
HINT: DTCs 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 -- END