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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.





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 see the undersurface of the seat cushion.

PROCEDURE

1. CHECK FOR DTC
(a) Turn the ignition switch ON.
(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 Removal.
(d) Turn the ignition switch OFF.
(e) Turn the ignition switch ON.
(f) Check for the 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.

OK -- USE SIMULATION METHOD TO CHECK
NG -- Continue to next step.
2. CHECK CONNECTION OF CONNECTOR
(a) Turn the ignition switch OFF.
(b) Disconnect the negative (-) terminal cable from the battery.
(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 -- REPAIR OR REPLACE WIRE HARNESS
OK -- Continue to next step.
4. CHECK OCCUPANT CLASSIFICATION SYSTEM CIRCUIT




(a) Connect the negative (-) terminal cable to the battery.
(b) Turn the ignition switch ON.
(c) Measure the voltage according to the value(s) in the table below.
Standard voltage:





(d) Turn the ignition switch OFF.
(e) Disconnect the negative (-) terminal cable from the battery.
(f) Using a service wire, connect terminals 16 (FSR+) and 24 (FSR-) of connector B.
NOTE:
Do not forcibly insert the service wire into the terminals of the connector when connecting the 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 FLOOR WIRE
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 negative (-) terminal cable to the battery.
(d) Turn the ignition switch ON.
(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 Reading and Clearing Diagnostic Trouble Codes.
(g) Turn the ignition switch OFF.
(h) Turn the ignition switch ON.
(i) Using the Techstream, check for the 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.

OK -- USE SIMULATION METHOD TO CHECK
NG -- Continue to next step.
6. REPLACE OCCUPANT CLASSIFICATION ECU
(a) Connect the Techstream to the DLC3.
(b) Turn the ignition switch ON.
(c) Using the Techstream, save the ECU data from the ECU which has been installed on the vehicle Registration.
(d) Turn the ignition switch OFF.
(e) Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.
(f) Replace the occupant classification ECU Disassembly.
(g) Connect the negative (-) terminal cable to the battery.
(h) Turn the ignition switch ON.
(i) Using the Techstream, load the previous ECU data stored into the new ECU Registration.
(j) Turn the ignition switch OFF.
(k) Turn the ignition switch ON.
(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. CHECK FOR DTC
(a) Turn the ignition switch ON.
(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 Reading and Clearing Diagnostic Trouble Codes.
(d) Turn the ignition switch OFF.
(e) Turn the ignition switch ON.
(f) Using the Techstream, check for the 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.

OK -- PERFORM SENSITIVITY CHECK
NG -- Continue to next step.
8. REPLACE CENTER AIRBAG SENSOR ASSEMBLY
(a) Turn the ignition switch OFF.
(b) Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.
(c) Replace the center airbag sensor Removal.
NEXT -- Continue to next step.
9. PERFORM SENSITIVITY CHECK
(a) Perform the sensitivity check Initialization.
NEXT -- END
10. CHECK FLOOR WIRE




(a) Turn the ignition switch OFF.
(b) Disconnect the negative (-) terminal cable from the battery, and wait for at least 90 seconds.
(c) Disconnect the front seat wire RH 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 ON.
(f) Measure the voltage according to the value(s) in the table below.
Standard voltage:





(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 -- REPAIR OR REPLACE FLOOR WIRE
OK -- REPAIR OR REPLACE FRONT SEAT WIRE RH
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