Center Airbag Sensor Assembly Communication Circuit Malfunction (B1790)

DESCRIPTION

The center airbag sensor assembly communication circuit consists of the occupant classification ECU and center airbag sensor assembly.

DTC B1790 is recorded when a malfunction is detected in the center airbag sensor assembly communication circuit.

DTC No.	DTC Detecting Condition	Trouble Area
B1790	The occupant classification ECU receives a line short circuit signal, an open circuit signal, a short circuit to ground signal or a short circuit to B+ signal in the center airbag sensor assembly communication circuit. Occupant classification ECU malfunction Center airbag sensor assembly malfunction	Occupant classification ECU Center airbag sensor assembly Front seat wire RH (for Power seat) Floor wire No. 2 Junction connector

WIRING DIAGRAM
CAUTION / NOTICE / HINT

HINT:

• If troubleshooting (wire harness inspection) is difficult to perform, remove the front passenger seat installation bolts to see the under surface of 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 CONNECTORS

(a) Turn the ignition switch off.

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

(c) for Power seat:

Check that the connectors are properly connected to the center airbag sensor assembly and occupant classification ECU. Also check that the connectors that link the front seat wire RH and No. 2 floor wire are properly connected.

(d) for Manual seat:

Check that the connectors are properly connected to the center airbag sensor assembly and occupant classification ECU.

OK:

The connectors are properly connected.

HINT:

If the connectors are not connected securely, reconnect the connectors and proceed to the next inspection.

(e) for Power seat:

Disconnect the connectors from the center airbag sensor assembly and occupant classification ECU. Also disconnect the connectors that link the front seat wire RH and No. 2 floor wire.

(f) for Manual seat:

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

(g) Check that the connector terminals are not damaged.

OK:

The terminals are not deformed or damaged.

Result

Result	Proceed to
OK	A
NG (for Power seat)	B
NG (for Manual seat)	C

B

REPLACE WIRE HARNESS

C

REPLACE NO. 2 FLOOR WIRE

A

1. CHECK VEHICLE CONDITION

(a) Check the passenger seat type.

A

for Manual seat

B

for Power seat

B

GO TO STEP 12

A

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

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

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

(c) Turn the ignition switch to ON.

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

Standard Voltage:

Tester Connection	Switch Condition	Specified Condition
M14-8 (FSR+) - Body ground	Ignition switch ON	Below 1 V
M14-4 (FSR-) - Body ground	Ignition switch ON	Below 1 V

Text in Illustration

*1	Occupant Classification ECU
*2	Center Airbag Sensor Assembly
*3	No. 2 Floor Wire
*4	Front view of wire harness connector (to Occupant Classification ECU)
*5	Connector C

NG

REPLACE NO. 2 FLOOR WIRE

OK

1. CHECK NO. 2 FLOOR WIRE (OPEN)

(a) Turn the ignition switch off.

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

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

NOTICE:

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

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
M14-8 (FSR+) - M14-4 (FSR-)	Always	Below 1 Ω

Text in Illustration

*1	Occupant Classification ECU	*2	Center Airbag Sensor Assembly
*3	No. 2 Floor Wire	*4	Front view of wire harness connector (to Center Airbag Sensor Assembly)
*5	Front view of wire harness connector (to Occupant Classification ECU)	*6	Connector B
*7	Connector C	-	-

NG

REPLACE NO. 2 FLOOR WIRE

OK

1. CHECK NO. 2 FLOOR WIRE (SHORT)

(a) Disconnect SST from connector B.

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
M14-8 (FSR+) - M14-4 (FSR-)	Always	1 MΩ or higher

Text in Illustration

*1	Occupant Classification ECU
*2	Center Airbag Sensor Assembly
*3	No. 2 Floor Wire
*4	Front view of wire harness connector (to Occupant Classification ECU)
*5	Connector C

NG

REPLACE NO. 2 FLOOR WIRE

OK

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

(a) Measure the resistance according to the value(s) in the table below. Standard Resistance: Tester Connection Condition Specified Condition M14-8 (FSR+) - Body ground Always 1 MΩ or higher M14-4 (FSR-) - Body ground Always 1 MΩ or higher Text in Illustration *1 Occupant Classification ECU *2 Center Airbag Sensor Assembly *3 No. 2 Floor Wire *4 Front view of wire harness connector (to Occupant Classification ECU) *5 Connector C

NG

REPLACE NO. 2 FLOOR WIRE

OK

1. RECHECK DTC

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

(b) Connect the Techstream to the DLC3.

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

(d) Turn the ignition switch to ON.

(e) Clear the DTCs stored in the occupant classification ECU (See page ).

(f) Clear the DTCs stored in the center airbag sensor assembly (See page ).

(g) Turn the ignition switch off.

(h) Turn the ignition switch to ON.

(i) Using the Techstream, check the DTCs of the occupant classification ECU (See page ).

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

OK

1. REPLACE OCCUPANT CLASSIFICATION ECU

(a) Turn the ignition switch off.

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

(c) Replace the occupant classification ECU (See page ).

HINT:

Perform the inspection using parts from a normal vehicle if possible.

NEXT

1. PERFORM ZERO POINT CALIBRATION

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

(b) Connect the Techstream to the DLC3.

(c) Turn the ignition switch to ON.

(d) Using the Techstream, perform Zero Point Calibration (See page ).

OK:

"Zero Point Calibration is complete." is displayed.

NEXT

1. PERFORM SENSITIVITY CHECK

(a) Using the Techstream, perform Sensitivity Check (See page ).

Standard:

27 to 33 kg (59.52 to 72.8 lb)

NEXT

1. RECHECK DTC

(a) Turn the ignition switch to ON.

(b) Clear the DTCs stored in the occupant classification ECU (See page ).

(c) Clear the DTCs stored in the center airbag sensor assembly (See page ).

(d) Turn the ignition switch off.

(e) Turn the ignition switch to ON.

(f) Using the Techstream, check the DTCs of the occupant classification ECU (See page ).

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

END

NG

REPLACE CENTER AIRBAG SENSOR ASSEMBLY

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

(a) Connect the connectors that link the front seat wire RH and No. 2 floor wire.

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

(c) Turn the ignition switch to ON.

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

Standard Voltage:

Tester Connection	Switch Condition	Specified Condition
S12-8 (FSR+) - Body ground	Ignition switch ON	Below 1 V
S12-4 (FSR-) - Body ground	Ignition switch ON	Below 1 V

Text in Illustration

*1	Occupant Classification ECU
*2	Center Airbag Sensor Assembly
*3	Junction Connector
*4	Front view of wire harness connector (to Occupant Classification ECU)
*5	Connector E

NG

GO TO STEP 21

OK

1. CHECK OCCUPANT CLASSIFICATION SYSTEM CIRCUIT (OPEN)

(a) Turn the ignition switch off.

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

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

NOTICE:

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

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
S12-8 (FSR+) - S12-4 (FSR-)	Always	Below 1 Ω

Text in Illustration

*1	Occupant Classification ECU	*2	Center Airbag Sensor Assembly
*3	Junction Connector	*4	Front view of wire harness connector (to Center Airbag Sensor Assembly)
*5	Front view of wire harness connector (to Occupant Classification ECU)	*6	Connector B
*7	Connector E	-	-

NG

GO TO STEP 23

OK

1. 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:

Tester Connection	Condition	Specified Condition
S12-8 (FSR+) - S12-4 (FSR-)	Always	1 MΩ or higher

Text in Illustration

*1	Occupant Classification ECU
*2	Center Airbag Sensor Assembly
*3	Junction Connector
*4	Front view of wire harness connector (to Occupant Classification ECU)
*5	Connector E

NG

GO TO STEP 25

OK

1. CHECK OCCUPANT CLASSIFICATION SYSTEM CIRCUIT (SHORT TO GROUND)

(a) Measure the resistance according to the value(s) in the table below. Standard Resistance: Tester Connection Condition Specified Condition S12-8 (FSR+) - Body ground Always 1 MΩ or higher S12-4 (FSR-) - Body ground Always 1 MΩ or higher Text in Illustration *1 Occupant Classification ECU *2 Center Airbag Sensor Assembly *3 Junction Connector *4 Front view of wire harness connector (to Occupant Classification ECU) *5 Connector E

NG

GO TO STEP 27

OK

1. RECHECK DTC

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

(b) Connect the Techstream to the DLC3.

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

(d) Turn the ignition switch to ON.

(e) Clear the DTCs stored in the occupant classification ECU (See page ).

(f) Clear the DTCs stored in the center airbag sensor assembly (See page ).

(g) Turn the ignition switch off.

(h) Turn the ignition switch to ON.

(i) Using the Techstream, check the DTCs of the occupant classification ECU (See page ).

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

1. REPLACE OCCUPANT CLASSIFICATION ECU

(a) Turn the ignition switch off.

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

(c) Replace the occupant classification ECU (See page ).

HINT:

Perform the inspection using parts from a normal vehicle if possible.

NEXT

1. PERFORM ZERO POINT CALIBRATION

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

(b) Connect the Techstream to the DLC3.

(c) Turn the ignition switch to ON.

(d) Using the Techstream, perform Zero Point Calibration (See page ).

OK:

"Zero Point Calibration is complete." is displayed.

NEXT

1. PERFORM SENSITIVITY CHECK

(a) Using the Techstream, perform Sensitivity Check (See page ).

Standard:

27 to 33 kg (59.5 to 72.8 lb)

NEXT

1. RECHECK DTC

(a) Turn the ignition switch to ON.

(b) Clear the DTCs stored in the occupant classification ECU (See page ).

(c) Clear the DTCs stored in the center airbag sensor assembly (See page ).

(d) Turn the ignition switch off.

(e) Turn the ignition switch to ON.

(f) Using the Techstream, check the DTCs of the occupant classification ECU (See page ).

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

END

NG

REPLACE CENTER AIRBAG SENSOR ASSEMBLY

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

(a) Turn the ignition switch off.

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

(c) Disconnect the junction connector from the No. 2 floor wire.

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

(e) Turn the ignition switch to ON.

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

Standard Voltage:

Tester Connection	Switch Condition	Specified Condition
M26-13 (FSR+) - Body ground	Ignition switch ON	Below 1 V
M26-14 (FSR-) - Body ground	Ignition switch ON	Below 1 V

Text in Illustration

*1	Occupant Classification ECU
*2	Center Airbag Sensor Assembly
*3	Front Seat Wire RH
*4	Junction Connector
*5	No. 2 Floor Wire
*6	Front view of wire harness connector (to Junction Connector)
*7	Connector C

NG

REPLACE NO. 2 FLOOR WIRE

OK

1. CHECK FRONT SEAT WIRE RH (SHORT TO B+)

(a) Turn the ignition 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 junction connector.

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

(e) Turn the ignition switch to ON.

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

Standard Voltage:

Tester Connection	Switch Condition	Specified Condition
S14-14 (FSR+) - Body ground	Ignition switch ON	Below 1 V
S14-13 (FSR-) - Body ground	Ignition switch ON	Below 1 V

Text in Illustration

*1	Occupant Classification ECU
*2	Center Airbag Sensor Assembly
*3	Front Seat Wire RH
*4	Junction Connector
*5	No. 2 Floor Wire
*6	Front view of wire harness connector (to Junction Connector)
*7	Connector D

OK

REPLACE JUNCTION CONNECTOR

NG

REPLACE FRONT SEAT WIRE RH

1. CHECK NO. 2 FLOOR WIRE (OPEN)

(a) Disconnect the junction 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:

Tester Connection	Condition	Specified Condition
M26-13 (FSR+) - M26-14 (FSR-)	Always	Below 1 Ω

Text in Illustration

*1	Occupant Classification ECU	*2	Center Airbag Sensor Assembly
*3	Front Seat Wire RH	*4	Junction Connector
*5	No. 2 Floor Wire	*6	Front view of wire harness connector (to Center Airbag Sensor Assembly)
*7	Front view of wire harness connector (to Junction Connector)	*8	Connector B
*9	Connector C	-	-

NG

REPLACE NO. 2 FLOOR WIRE

OK

1. CHECK FRONT SEAT WIRE RH (OPEN)

(a) Disconnect the front seat wire RH connector from the junction connector.

(b) Using SST, connect terminals 8 (FSR+) and 4 (FSR-) of connector E.

NOTICE:

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

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
S14-14 (FSR+) - S14-13 (FSR-)	Always	Below 1 Ω

Text in Illustration

*1	Occupant Classification ECU	*2	Center Airbag Sensor Assembly
*3	Front Seat Wire RH	*4	Junction Connector
*5	No. 2 Floor Wire	*6	Front view of wire harness connector (to Junction Connector)
*7	Front view of wire harness connector (to Occupant Classification ECU)	*8	Connector D
*9	Connector E	-	-

OK

REPLACE JUNCTION CONNECTOR

NG

REPLACE FRONT SEAT WIRE RH

1. CHECK NO. 2 FLOOR WIRE (SHORT)

(a) Disconnect the junction connector from the No. 2 floor wire.

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
M26-13 (FSR+) - M26-14 (FSR-)	Always	1 MΩ or higher

Text in Illustration

*1	Occupant Classification ECU
*2	Center Airbag Sensor Assembly
*3	Front Seat Wire RH
*4	Junction Connector
*5	No. 2 Floor Wire
*6	Front view of wire harness connector (to Junction Connector)
*7	Connector C

NG

REPLACE NO. 2 FLOOR WIRE

OK

1. CHECK FRONT SEAT WIRE RH (SHORT)

(a) Disconnect the front seat wire RH connector from the junction connector.

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
S14-14 (FSR+) - S14-13 (FSR-)	Always	1 MΩ or higher

Text in Illustration

*1	Occupant Classification ECU
*2	Center Airbag Sensor Assembly
*3	Front Seat Wire RH
*4	Junction Connector
*5	No. 2 Floor Wire
*6	Front view of wire harness connector (to Junction Connector)
*7	Connector D

OK

REPLACE JUNCTION CONNECTOR

NG

REPLACE FRONT SEAT WIRE RH

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

(a) Disconnect the junction connector from the No. 2 floor wire.

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
M26-13 (FSR+) - Body ground	Always	1 MΩ or higher
M26-14 (FSR-) - Body ground	Always	1 MΩ or higher

Text in Illustration

*1	Occupant Classification ECU
*2	Center Airbag Sensor Assembly
*3	Front Seat Wire RH
*4	Junction Connector
*5	No. 2 Floor Wire
*6	Front view of wire harness connector (to Junction Connector)
*7	Connector C

NG

REPLACE NO. 2 FLOOR WIRE

OK

1. CHECK FRONT SEAT WIRE RH (SHORT TO GROUND)

(a) Disconnect the front seat wire RH connector from the junction connector.

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
S14-14 (FSR+) - Body ground	Always	1 MΩ or higher
S14-13 (FSR-) - Body ground	Always	1 MΩ or higher

Text in Illustration

*1	Occupant Classification ECU
*2	Center Airbag Sensor Assembly
*3	Front Seat Wire RH
*4	Junction Connector
*5	No. 2 Floor Wire
*6	Front view of wire harness connector (to Junction Connector)
*7	Connector D

OK

REPLACE JUNCTION CONNECTOR

NG

REPLACE FRONT SEAT WIRE RH