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B1790








SUPPLEMENTAL RESTRAINT SYSTEMS: 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 stored when a malfunction is detected in the center airbag sensor communication circuit.





HINT: When DTC B1650 is stored 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 it first.

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 fall down.

PROCEDURE

1. CHECK FOR 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. DTC Check / Clear
(d) Turn the engine switch off.
(e) Turn the engine 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 -- CHECK CONNECTION OF CONNECTOR
OK -- USE SIMULATION METHOD TO CHECK
2. CHECK CONNECTION OF CONNECTOR
(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.
OK:
Connectors are properly connected.
NG -- CONNECT CONNECTORS PROPERLY
OK -- Continue to next step.
3. CHECK CONNECTOR
(a) Disconnect the connectors from the center airbag sensor and the occupant classification ECU.
(b) Check that the connectors (on the center airbag sensor side and occupant classification ECU side) are not damaged.
OK:
Connectors are not deformed or damaged.
NG -- REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.
4. CHECK OCCUPANT CLASSIFICATION SYSTEM CIRCUIT





(a) Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.
(b) Turn the engine switch on (IG).
(c) Measure the voltage according to the value(s) in the table below.
Standard Voltage:





(d) Turn the engine switch off.
(e) Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
(f) Using a service wire, connect terminals 16 (FSR+) and 22 (FSR-) of connector B.
NOTE: Do not forcibly insert the service wire into the terminals of the connector when connecting a service wire.
(g) Measure the resistance according to the value(s) in the table below.
Standard Resistance:





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






NG -- CHECK NO. 2 FLOOR WIRE (CENTER AIRBAG SENSOR - FRONT SEAT WIRE RH)
OK -- Continue to next step.
5. CHECK FOR DTC
(a) Connect the connectors to the occupant classification ECU and the center airbag sensor.
(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. 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 NO. 1 SEAT CUSHION ASSEMBLY (OCCUPANT CLASSIFICATION ECU)
OK -- USE SIMULATION METHOD TO CHECK
6. REPLACE NO. 1 SEAT CUSHION ASSEMBLY (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 which is installed in the vehicle. Registration
(d) Turn the engine switch off.
(e) Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
(f) Replace the No. 1 seat cushion (occupant classification ECU).
(g) Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.
(h) Turn the engine switch on (IG).
(i) Using the Techstream, load the previous ECU data stored in the Techstream 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.
7. PERFORM ZERO POINT CALIBRATION
(a) Connect the Techstream to the DLC3.
(b) Turn the engine switch on (IG).
(c) Using the Techstream, perform zero point calibration. Initialization
(d) Turn the engine switch off.
(e) Turn the engine switch on (IG).
(f) Clear the DTCs stored in the occupant classification ECU. 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. CHECK FOR 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. 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.
NEXT -- Continue to next step.
11. PERFORM SENSITIVITY CHECK
(a) Perform the sensitivity check. Initialization
NEXT -- END
12. CHECK NO. 2 FLOOR WIRE (CENTER AIRBAG SENSOR - FRONT SEAT WIRE RH)





(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 No. 2 floor wire.
(d) Connect the cable to the negative (-) battery terminal, and wait for at least 2 seconds.
(e) Turn the engine switch on (IG).
(f) Measure the voltage according to the value(s) in the table below.
Standard Voltage:





(g) Turn the engine switch off.
(h) Disconnect the cable from the negative (-) battery terminal, and wait for at least 90 seconds.
(i) Disconnect the front seat wire RH connector from the No. 2 floor wire.
(j) Using service wire, connect terminals 16 (FSR+) and 22 (FSR-) of connector B.
NOTE: Do not forcibly insert the service wire into the terminals of the connector when connecting a service wire.
(k) Measure the resistance according to the value(s) in the table below.
Standard Resistance:





(l) Disconnect the service wire from connector B.
(m) 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
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