Toyota Tacoma manuals

Toyota Tacoma (2015-2018) Service Manual: Front Occupant Classification Sensor RH Circuit Malfunction (B1781)

Toyota Tacoma (2015-2018) Service Manual / Supplemental Restraint Systems / Occupant Classification System / Front Occupant Classification Sensor RH Circuit Malfunction (B1781)

DESCRIPTION

The front occupant classification sensor RH circuit consists of the occupant detection ECU and the front occupant classification sensor RH.

DTC B1781 is set when a malfunction is detected in the front occupant classification sensor RH circuit.

DTC No.

DTC Detecting Conditions

Trouble Areas

B1781
  • The occupant detection 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 front occupant classification sensor RH circuit for 2 seconds
  • Occupant classification sensor front RH malfunction
  • Occupant detection ECU malfunction
  • Front seat with adjuster frame assembly RH (Front occupant classification sensor RH)
  • No. 1 seat wire
  • Occupant detection ECU

HINT:

  • When DTC B1650/32 is detected as a result of troubleshooting the supplemental restraint system, perform troubleshooting for DTC B1781 of the occupant classification system.
  • Use the Techstream to check for DTCs of the occupant detection ECU, otherwise the DTC cannot be read.

WIRING DIAGRAM

CAUTION / NOTICE / HINT

CAUTION / NOTICE / HINT

HINT:

  • If troubleshooting (wire harness inspection) is difficult to perform, remove the front RH seat assembly installation bolts to see the under surface 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 problems, such as seat rail deformation. Hold the seat up only for as long as necessary.

PROCEDURE

1.

CHECK DTC

(a) Turn the ignition switch to the ON position.

(b) Clear any DTCs stored in the memory (See page ).

HINT:

  • First clear DTCs stored in the occupant detection ECU and then in the airbag sensor assembly.
  • Use the Techstream to clear the DTCs of the occupant detection ECU, otherwise the DTCs cannot be cleared.

(c) Turn the ignition switch to the LOCK position.

(d) Turn the ignition switch to the ON position.

(e) Using the Techstream, check for DTCs of the occupant detection ECU (See page OK: ).

OK:

DTC B1781 is not output.

HINT:

DTCs other than B1781 may be output at this time, but they are not related to this check.

OK

USE SIMULATION METHOD TO CHECK
NG

2.

CHECK CONNECTION OF CONNECTORS

(a) Turn the ignition switch to the LOCK position.

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

(c) Check that the connectors are properly connected to the occupant detection ECU and the front occupant classification sensor RH.

OK:

The connectors are properly connected.

NG

OTHERS CONNECTORS
OK

3.

CHECK CONNECTORS

(a) Check that the connectors (on the occupant detection ECU side and front occupant classification sensor RH side) are not damaged (See page OK: ).

OK:

The connectors are not deformed or damaged.

NG

REPAIR OR REPLACE WIRE HARNESS
OK

4.

CHECK NO. 1 SEAT WIRE (TO B+)

(a) Disconnect the connectors from the occupant detection ECU and the front occupant classification sensor RH.

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

(c) Turn the ignition switch to the ON position.

(d) Measure the voltage.

Standard voltage:

Tester Connection

Condition

Specified Condition

O4-2 (SGD2) - Body ground

Ignition switch ON

Below 1 V

O4-8 (SIG2) - Body ground

Ignition switch ON

Below 1 V

O4-12 (SVC2) - Body ground

Ignition switch ON

Below 1 V
NG

REPAIR OR REPLACE NO. 1 SEAT WIRE
OK

5.

CHECK NO. 1 SEAT WIRE (FOR OPEN)

(a) Turn the ignition switch to the LOCK position.

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

(c) Using service wires, connect O7-1 (SVC2) and O7-3 (SGD2), and connect O7-2 (SIG2) and O7-3 (SGD2) of connector C.

NOTICE:

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

(d) Measure the resistance.

Standard resistance:

Tester Connection

Condition

Specified Condition

O4-8 (SIG2) - O4-2 (SGD2)

Always

Below 1 Ω

O4-12 (SVC2) - O4-2 (SGD2)

Always

Below 1 Ω
NG

REPAIR OR REPLACE NO. 1 SEAT WIRE
OK

6.

CHECK NO. 1 SEAT WIRE (FOR SHORT)

(a) Disconnect the service wires from connector C.

(b) Measure the resistance.

Standard resistance:

Tester Connection

Condition

Specified Condition

O4-8 (SIG2) - O4-2 (SGD2)

Always

1 MΩ or higher

O4-12 (SVC2) - O4-2 (SGD2)

Always

1 MΩ or higher

O4-8 (SIG2) - O4-12 (SVC2)

Always

1 MΩ or higher
NG

REPAIR OR REPLACE NO. 1 SEAT WIRE
OK

7.

CHECK NO. 1 SEAT WIRE (TO GROUND)

(a) Measure the resistance.

Standard resistance:

Tester Connection

Condition

Specified Condition

O4-2 (SGD2) - Body ground

Always

1 MΩ or higher

O4-8 (SIG2) - Body ground

Always

1 MΩ or higher

O4-12 (SVC2) - Body ground

Always

1 MΩ or higher
NG

REPAIR OR REPLACE NO. 1 SEAT WIRE
OK

8.

CHECK DTC

(a) Connect the connectors to the occupant detection ECU and the front occupant classification sensor RH.

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

(c) Turn the ignition switch to the ON position.

(d) Clear any DTCs stored in the memory (See page ).

HINT:

  • First clear DTCs stored in the occupant detection ECU and then in the airbag sensor assembly.
  • Use the Techstream to clear the DTCs of the occupant detection ECU, otherwise the DTCs cannot be cleared.

(e) Turn the ignition switch to the LOCK position.

(f) Turn the ignition switch to the ON position.

(g) Using the Techstream, check for DTCs of the occupant detection ECU (See page OK: ).

OK:

DTC B1781 is not output.

HINT:

DTCs other than B1781 may be output at this time, but they are not related to this check.

OK

USE SIMULATION METHOD TO CHECK
NG

9.

REPLACE OCCUPANT DETECTION ECU

(a) Turn the ignition switch to the LOCK position.

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

(c) Replace the occupant detection ECU (See page HINT: HINT: ).

HINT:

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

NEXT

10.

PERFORM ZERO POINT CALIBRATION

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

(b) Connect the Techstream to the DLC3.

(c) Turn the ignition switch to the ON position.

(d) Using the Techstream, perform the zero point calibration (See page OK: ).

OK:

"Zero Point Calibration is complete." is displayed on the Techstream.

NG

GO TO STEP 13

OK

11.

PERFORM SENSITIVITY CHECK

(a) Using the Techstream, perform the sensitivity check (See page Standard value: ).

Standard value:

27 to 33 kg (59.52 to 72.75 lb)

NG

GO TO STEP 13

OK

12.

CHECK DTC

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

(b) Turn the ignition switch to the ON position.

(c) Clear any DTCs stored in the memory (See page ).

HINT:

  • First clear DTCs stored in the occupant detection ECU and then in the airbag sensor assembly.
  • Use the Techstream to clear the DTCs of the occupant detection ECU, otherwise the DTCs cannot be cleared.

(d) Turn the ignition switch to the LOCK position.

(e) Turn the ignition switch to the ON position.

(f) Using the Techstream, check for DTCs of the occupant detection ECU (See page OK: ).

OK:

DTC B1781 is not output.

HINT:

DTCs other than B1781 may be output at this time, but they are not related to this check.

OK

USE SIMULATION METHOD TO CHECK
NG

13.

REPLACE FRONT SEAT WITH ADJUSTER FRAME ASSEMBLY RH

(a) Turn the ignition switch to the LOCK position.

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

(c) Replace the front seat with adjuster frame assembly RH (See page ).

NEXT

14.

PERFORM ZERO POINT CALIBRATION

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

(b) Connect the Techstream to the DLC3.

(c) Turn the ignition switch to the ON position.

(d) Using the Techstream, perform the zero point calibration (See page OK: ).

OK:

"Zero Point Calibration is complete." is displayed on the Techstream.

NEXT

15.

PERFORM SENSITIVITY CHECK

(a) Using the Techstream, perform the sensitivity check (See page Standard value: ).

Standard value:

27 to 33 kg (59.52 to 72.75 lb)

NEXT

USE SIMULATION METHOD TO CHECK
Passenger Side Buckle Switch Circuit Malfunction (B1771)
DESCRIPTION The passenger side buckle switch circuit consists of the occupant detection ECU and the front seat inner belt assembly RH. DTC B1771 is recorded when a malfunction is detected in the p ...

Front Occupant Classification Sensor LH Circuit Malfunction (B1780)
DESCRIPTION The occupant classification sensor front LH circuit consists of the occupant detection ECU and the occupant classification sensor front LH. DTC B1780 is set when a malfunction is detec ...

Other materials:

Fail-safe Chart
FAIL-SAFE CHART If there is a problem with sensor signals or actuator systems, the skid control ECU prohibits power supply to the brake actuator assembly and informs the ECM of a VSC system malfunction. The brake actuator assembly turns off the solenoids and the ECM stops its ...

Center Differential Lock Position Switch (C1282)
DESCRIPTION DTC C1282 is stored only in test mode. DTC Code DTC Detection Condition Trouble Area C1282 Stored during test mode. Harness or connector Transfer system Skid control ECU (master cylinder sole ...

Parking brake
Lever type ● Sets the parking brake Fully set the parking brake while depressing the brake pedal. At this time, the indicator will come on. ● Release the parking brake Press the button Turn the lever clockwise Press it in completely Pedal type Sets the parking brake*. ...

© 2011-2026 Copyright www.ttguide.net