Toyota CH-R Service Manual: Front Occupant Classification Sensor LH Circuit Malfunction (B1780)

Toyota CH-R Service Manual / Supplemental Restraint Systems / Occupant Classification System / Front Occupant Classification Sensor LH Circuit Malfunction (B1780)

DESCRIPTION

The front occupant classification sensor LH circuit consists of the occupant detection ECU and front in weight detection sensor sub-assembly.

DTC B1780 is stored when a malfunction is detected in the front in weight detection sensor sub-assembly circuit.

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

B1780

Front Occupant Classification Sensor LH Circuit Malfunction

Any of the following conditions is met:

  • The occupant detection ECU detects a line short in the front in weight detection sensor sub-assembly circuit.
  • The occupant detection ECU detects a line short to ground in the front in weight detection sensor sub-assembly circuit.
  • The occupant detection ECU detects a line short to B+ in the front in weight detection sensor sub-assembly circuit.
  • The occupant detection ECU detects a line open in the front in weight detection sensor sub-assembly circuit.
  • Front in weight detection sensor sub-assembly malfunction
  • Occupant detection ECU malfunction
  • Front seat wire RH
  • Front in weight detection sensor sub-assembly (Front seat adjuster assembly RH)*
  • Occupant detection ECU
  • *: The front in weight detection sensor sub-assembly is built into the front seat adjuster assembly RH.
DTC Detection Conditions
 

Vehicle Condition

Pattern 1

Pattern 2

Pattern 3

Pattern 4

Pattern 5

Pattern 6

Diagnosis Condition

Ignition switch ON

○

○

○

○

○

○

Malfunction Status

The occupant detection ECU detects a line short in the front in weight detection sensor sub-assembly circuit.

○

-

-

-

-

-

The occupant detection ECU detects a line short to ground in the front in weight detection sensor sub-assembly circuit.

-

○

-

-

-

-

The occupant detection ECU detects a line short to B+ in the front in weight detection sensor sub-assembly circuit.

-

-

○

-

-

-

The occupant detection ECU detects a line open in the front in weight detection sensor sub-assembly circuit.

-

-

-

○

-

-

Front in weight detection sensor sub-assembly malfunction

-

-

-

-

○

-

Occupant detection ECU malfunction

-

-

-

-

-

○

Detection Time

-

-

-

-

-

-

Number of Trips

1 trip

1 trip

1 trip

1 trip

1 trip

1 trip

HINT:

DTC will be output when conditions for either of the patterns in the table above are met.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

After turning the ignition switch off, waiting time may be required before disconnecting the cable from the negative (-) battery terminal. Therefore, make sure to read the disconnecting the cable from the negative (-) battery terminal notices before proceeding with work.

Click here

HINT:

  • When DTC B1650/32 is stored as a result of troubleshooting for the airbag system, check the DTCs stored in the occupant detection ECU. When DTC B1780 is output, perform troubleshooting for this DTC first.
  • If it is difficult to perform troubleshooting (wire harness inspection), remove the front passenger seat installation bolts to see under the seat cushion.
  • In the above case, lift and hold the seat so that it does not fall down. Hold the seat only as necessary because holding the seat for a long period of time may cause seat rail deformation.

PROCEDURE

1.

CHECK CONNECTORS

(a) Turn the ignition switch off.

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

(c) Check that the connectors are properly connected to the occupant detection ECU and front in weight detection sensor sub-assembly.

OK:

The connectors are properly connected.

HINT:

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

(d) Disconnect the connectors from the occupant detection ECU and front in weight detection sensor sub-assembly.

(e) Check that the terminals of the connectors are not deformed or damaged.

OK:

The terminals are not deformed or damaged.

NG

REPLACE FRONT SEAT WIRE RH
OK

2.

CHECK FRONT SEAT WIRE RH (SHORT TO B+)

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

*1

Front In Weight Detection Sensor Sub-assembly

*2

Occupant Detection ECU

*3

Front Seat Wire RH

*a

Front view of wire harness connector

(to Occupant Detection ECU)

(b) Turn the ignition switch to ON.

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

Standard Voltage:

Tester Connection

Switch Condition

Specified Condition

Y5-1 (SVC1) - Body ground

Ignition switch ON

Below 1 V

Y5-3 (SIG1) - Body ground

Ignition switch ON

Below 1 V

Y5-5 (SGD1) - Body ground

Ignition switch ON

Below 1 V

(d) Turn the ignition switch off.

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

NG

GO TO STEP 12

OK

3.

CHECK FRONT SEAT WIRE RH (OPEN)

(a) Using service wires, connect terminals 1 (SVC) and 3 (SGD), and terminals 2 (SIG) and 3 (SGD) of connector C.

NOTICE:

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

*1

Front In Weight Detection Sensor Sub-assembly

*2

Occupant Detection ECU

*3

Front Seat Wire RH

*4

Service Wire

*a

Front view of wire harness connector

(to Occupant Detection ECU)

*b

Front view of wire harness connector

(to Front In Weight Detection Sensor Sub-assembly)

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

Y5-1 (SVC1) - Y5-5 (SGD1)

Always

Below 1 Ω

Y5-3 (SIG1) - Y5-5 (SGD1)

Always

Below 1 Ω

(c) Disconnect the service wires from connector C.

NG

REPLACE FRONT SEAT WIRE RH
OK

4.

CHECK FRONT SEAT WIRE RH (SHORT)

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

Y5-1 (SVC1) - Y5-5 (SGD1)

Always

1 MΩ or higher

Y5-3 (SIG1) - Y5-5 (SGD1)

Always

1 MΩ or higher

Y5-1 (SVC1) - Y5-3 (SIG1)

Always

1 MΩ or higher

*1

Front In Weight Detection Sensor Sub-assembly

*2

Occupant Detection ECU

*3

Front Seat Wire RH

*a

Front view of wire harness connector

(to Occupant Detection ECU)
NG

REPLACE FRONT SEAT WIRE RH
OK

5.

CHECK FRONT SEAT WIRE RH (SHORT TO GROUND)

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

Y5-1 (SVC1) - Body ground

Always

1 MΩ or higher

Y5-3 (SIG1) - Body ground

Always

1 MΩ or higher

Y5-5 (SGD1) - Body ground

Always

1 MΩ or higher

*1

Front In Weight Detection Sensor Sub-assembly

*2

Occupant Detection ECU

*3

Front Seat Wire RH

*a

Front view of wire harness connector

(to Occupant Detection ECU)
NG

REPLACE FRONT SEAT WIRE RH
OK

6.

CHECK DTC

(a) Connect the connectors to the occupant detection ECU and front in weight detection sensor sub-assembly.

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

(c) Clear the DTCs stored in the occupant detection ECU.

Click here

Body Electrical > Occupant Detection > Clear DTCs

(d) Clear the DTCs stored in the airbag sensor assembly.

Click here

Body Electrical > SRS Airbag > Clear DTCs

(e) Turn the ignition switch off.

(f) Turn the ignition switch to ON, and wait for at least 10 seconds.

(g) Check for DTCs.

Click here

Body Electrical > Occupant Detection > Trouble Codes

OK:

DTC B1780 is not output.

HINT:

Codes other than DTC B1780 may be output at this time, but they are not related to this check.

(h) Turn the ignition switch off.

OK

USE SIMULATION METHOD TO CHECK

NG

7.

CHECK OCCUPANT DETECTION ECU

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

(b) Replace the occupant detection ECU with a known good one.

Click here

HINT:

Perform the following inspection using known good parts from another vehicle if possible.

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

(d) Clear the DTCs stored in the occupant detection ECU.

Click here

Body Electrical > Occupant Detection > Clear DTCs

(e) Clear the DTCs stored in the airbag sensor assembly.

Click here

Body Electrical > SRS Airbag > Clear DTCs

(f) Turn the ignition switch off.

(g) Turn the ignition switch to ON, and wait for at least 10 seconds.

(h) Check for DTCs.

Click here

Body Electrical > Occupant Detection > Trouble Codes

OK:

DTC B1780 is not output.

HINT:

Codes other than DTC B1780 may be output at this time, but they are not related to this check.

(i) Turn the ignition switch off.

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

(k) Restore the occupant detection ECU that was installed for testing to its original location.

Click here

NG

GO TO STEP 10

OK

8.

REPLACE OCCUPANT DETECTION ECU

(a) Turn the ignition switch off.

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

(c) Replace the occupant detection ECU with a new one.

Click here

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

NEXT

9.

PERFORM ZERO POINT CALIBRATION

(a) Using the Techstream, perform Zero Point Calibration.

Click here

Body Electrical > Occupant Detection > Utility

Tester Display

Zero Point Calibration
NEXT

END

10.

REPLACE FRONT SEAT ADJUSTER ASSEMBLY RH

(a) Turn the ignition switch off.

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

(c) Replace the front seat adjuster assembly RH.

Click here

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

NEXT

11.

PERFORM ZERO POINT CALIBRATION

(a) Using the Techstream, perform Zero Point Calibration.

Click here

Body Electrical > Occupant Detection > Utility

Tester Display

Zero Point Calibration
NEXT

END

12.

REPLACE FRONT SEAT ADJUSTER ASSEMBLY RH

(a) Replace the front seat adjuster assembly RH.

Click here

NOTICE:

Replace the front seat wire RH at the same time.

HINT:

When the front seat wire RH has a short to B+, the front in weight detection sensor sub-assembly will be damaged. Therefore, replace the front seat wire RH and the front seat adjuster assembly RH, which includes the front in weight detection sensor sub-assembly.

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

NEXT

13.

PERFORM ZERO POINT CALIBRATION

(a) Using the Techstream, perform Zero Point Calibration.

Click here

Body Electrical > Occupant Detection > Utility

Tester Display

Zero Point Calibration
NEXT

END
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