Toyota Tundra Service Manual: Occupant Classification Sensor Power Supply Circuit Malfunction (B1793)

Toyota Tundra Service Manual / Vehicle Interior / Supplemental Restraint Systems / Occupant Classification System / Occupant Classification Sensor Power Supply Circuit Malfunction (B1793)

DESCRIPTION

The occupant detection sensor power supply circuit consists of the occupant classification ECU and the occupant detection sensors.

DTC B1793 is set when a malfunction is detected in the occupant detection sensor power supply circuit.

DTC Code

DTC Detection Condition

Trouble Area

B1793

One of following conditions is met:

  • Occupant classification ECU receives line short circuit signal, open circuit signal, short circuit to ground signal or short circuit to +B signal in occupant detection sensor power supply circuit for 2 seconds
  • Open circuit in occupant detection sensor wire harness
  • Occupant classification ECU malfunction
  • Front seat frame with adjuster RH (Occupant detection sensors)
  • Front seat wire RH
  • Occupant classification ECU

HINT:

  • When DTC B1650/32 is detected as a result of troubleshooting the airbag system, perform troubleshooting for DTC B1793 of the occupant classification system.
  • Use the Techstream to check for DTCs of the occupant classification ECU, otherwise the DTCs cannot be read.

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 (See page ).
  • When disconnecting the cable from the negative (-) battery terminal while performing repairs, some systems need to be initialized after the cable is reconnected (See page ).

HINT:

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

PROCEDURE

1.

CHECK FOR DTC

(a) Turn the ignition switch to ON, and wait for at least 60 seconds.

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

HINT:

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

(c) Turn the ignition switch off.

(d) Turn the ignition switch to ON, and wait for at least 60 seconds.

(e) Using the Techstream, check for DTCs of the occupant classification ECU (see page ).

OK:

DTC B1793 is not output.

HINT:

DTCs other than DTC B1793 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 off.

(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 classification ECU and the occupant detection sensors.

OK:

Connectors are properly connected.

NG

CONNECT CONNECTORS

OK

3.

CHECK CONNECTORS

(a) Check that the connectors (on the occupant classification ECU side and the occupant detection sensors side) are not damaged (see page ).

OK:

Connectors are not deformed or damaged.

NG

REPLACE FRONT SEAT WIRE RH

OK

4.

CHECK FRONT SEAT WIRE RH

(a) Disconnect the connectors from the occupant classification ECU and the 4 occupant detection sensors.

(b) Connect the negative (-) terminal cable to the battery, and wait for at least 2 seconds.

(c) Turn the ignition switch to ON, and wait for at least 60 seconds.

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

Standard voltage:

Tester Connection

Switch Condition

Specified Condition

Y1-11 (SVC1) - Body ground

Ignition switch ON

Below 1 V

Y1-12 (SVC2) - Body ground

Y1-5 (SVC3) - Body ground

Y1-6 (SVC4) - Body ground

(e) Turn the ignition switch off.

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

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

Standard resistance:

Tester Connection

Switch Condition

Specified Condition

Y1-11 (SVC1) - Y4-1 (SVC)

Always

Below 1 Ω

Y1-12 (SVC2) - Y5-1 (SVC)

Y1-5 (SVC3) - Y6-1 (SVC)

Y1-6 (SVC4) - Y7-1 (SVC)

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

Standard resistance:

Tester Connection

Condition

Specified Condition

Y1-11 (SVC1) - Body ground

Always

1 MΩ or higher

Y1-12 (SVC2) - Body ground

Y1-5 (SVC3) - Body ground

Y1-6 (SVC4) - Body ground

Y1-11 (SVC1) - Y1-12 (SVC)

Y1-11 (SVC1) - Y1-6 (SVC)

Y1-12 (SVC2) - Y1-5 (SVC)

Y1-12 (SVC2) - Y1-6 (SVC)

Y1-11 (SVC1) - Y1-5 (SVC)

Y1-5 (SVC3) - Y1-6 (SVC)

NG

REPLACE FRONT SEAT WIRE RH

OK

5.

CHECK FOR DTC

(a) Connect the connectors to the occupant classification ECU and the 4 occupant detection sensors.

(b) Connect the negative (-) terminal cable to the battery, and wait for at least 2 seconds.

(c) Turn the ignition switch to ON, and wait for at least 60 seconds.

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

HINT:

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

(e) Turn the ignition switch off.

(f) Turn the ignition switch to ON, and wait for at least 60 seconds.

(g) Using the Techstream, check for DTCs of the occupant classification ECU (see page ).

OK:

DTC B1793 is not output.

HINT:

DTCs other than DTC B1793 may be output at this time, but they are not related to this check.

OK

USE SIMULATION METHOD TO CHECK

NG

6.

REPLACE OCCUPANT CLASSIFICATION ECU

(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 occupant classification ECU.

  • for Manual Seat (see page )
  • for Power Seat (see page )

HINT:

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

NEXT

7.

PERFORM ZERO POINT CALIBRATION

(a) Connect the negative (-) terminal cable to the battery, and wait for at least 2 seconds.

(b) Connect the Techstream to the DLC3.

(c) Turn the ignition switch to ON, and wait for at least 60 seconds.

(d) Using the Techstream, perform the zero point calibration (see page ).

NEXT

8.

PERFORM SENSITIVITY CHECK

(a) Using the Techstream, perform the sensitivity check (see page ).

Standard range:

27 to 33 kg (59.5 to 72.8 lb)

NEXT

END

    Center Airbag Sensor Assembly Communication Circuit Malfunction (B1790)

    Open in Occupant Classification ECU Battery Positive Line (B1794)

    See More:

    Toyota Tundra Service Manual > Forward Recognition Camera System: Power Source Circuit
    DESCRIPTION This circuit provides power to operate the forward recognition camera. WIRING DIAGRAM CAUTION / NOTICE / HINT NOTICE: Inspect the fuses for circuits related to this system before performing the following inspection procedure. PROCEDURE 1. CHECK HARNESS AND CONNECTOR (POWER SOURCE VOLTAGE ...

    Toyota Tundra Owners Manual

    Toyota Tundra Service Manual

    © 2024 Copyright www.ttundra.com
    0.0129