B1790

SUPPLEMENTAL RESTRAINT SYSTEM: 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 see 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 cause a problem, such as seat rail deformation. Hold the seat only as necessary.

PROCEDURE

1. CHECK 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 Reading and Clearing Diagnostic Trouble Codes.

(d) Turn the engine switch off.

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

(f) Check 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 Diagnosis System
NG -- Continue to next step.

2. CHECK CONNECTION OF CONNECTORS

(a) Turn the engine 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 assembly.

OK:

The connectors are properly connected.

NG -- CONNECT CONNECTORS PROPERLY, THEN GO TO STEP 1
OK -- Continue to next step.

3. CHECK CONNECTORS

(a) Disconnect the connectors from the center airbag sensor assembly and the occupant classification ECU.

(b) Check that the connectors (on the center airbag sensor assembly side and occupant classification ECU side) are not damaged.

OK:

The connectors are not deformed or damaged.

NG -- REPAIR OR REPLACE WIRE HARNESS
OK -- Continue to next step.

4. CHECK OCCUPANT CLASSIFICATION SYSTEM CIRCUIT (SHORT TO B+)

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

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

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

Standard voltage:

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

5. CHECK OCCUPANT CLASSIFICATION SYSTEM CIRCUIT (OPEN)

(a) Turn the engine switch off.

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

(c) Using a service wire, connect terminals 16 (FSR+) and 24 (FSR-) of connector B.

NOTICE:
Do not forcibly insert a service wire into the terminals of the connector when connecting the wire.

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

Standard resistance:

NG -- CHECK FLOOR WIRE NO. 2 (OPEN)
OK -- Continue to next step.

6. CHECK OCCUPANT CLASSIFICATION SYSTEM CIRCUIT (SHORT)

(a) Disconnect the service wire from connector B.

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

Standard resistance:

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

7. 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 NO. 2 (SHORT TO GROUND)
OK -- Continue to next step.

8. RECHECK DTC

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

(b) Connect Techstream to the DLC3.

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

(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 Reading and Clearing Diagnostic Trouble Codes.

(g) Turn the engine switch off.

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

(i) Using Techstream, check 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 Diagnosis System
NG -- Continue to next step.

9. REPLACE OCCUPANT CLASSIFICATION ECU

(a) Connect Techstream to the DLC3.

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

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

(d) Turn the engine switch off.

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

(f) Replace the occupant classification ECU Removal.

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

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

(i) Using 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.

10. 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 Reading and Clearing Diagnostic Trouble Codes.

(d) Turn the engine switch off.

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

(f) Using Techstream, check 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.

11. REPLACE CENTER AIRBAG SENSOR ASSEMBLY

(a) Turn the engine switch off.

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

(c) Replace the center airbag sensor assembly Removal.

NEXT -- Continue to next step.

12. PERFORM SENSITIVITY CHECK

(a) Perform the sensitivity check Initialization.

NEXT -- END

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

(a) Turn the engine 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 No. 2.

(d) Connect the negative (-) terminal cable to the battery, 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:

NG -- REPAIR OR REPLACE FLOOR WIRE NO. 2

OK -- REPAIR OR REPLACE FRONT SEAT WIRE RH

14. CHECK FLOOR WIRE NO. 2 (OPEN)

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

HINT
The service wire has already been inserted into connector B.

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

Standard resistance:

NG -- REPAIR OR REPLACE FLOOR WIRE NO. 2

OK -- REPAIR OR REPLACE FRONT SEAT WIRE RH

15. CHECK FLOOR WIRE NO. 2 (SHORT)

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

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

Standard resistance:

NG -- REPAIR OR REPLACE FLOOR WIRE NO. 2

OK -- REPAIR OR REPLACE FRONT SEAT WIRE RH

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

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

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

Standard resistance:

NG -- REPAIR OR REPLACE FLOOR WIRE NO. 2

OK -- REPAIR OR REPLACE FRONT SEAT WIRE RH