Toyota Tundra Service Manual: Front Occupant Classification Sensor LH Collision Detection (B1785)

Toyota Tundra Service Manual / Vehicle Interior / Supplemental Restraint Systems / Occupant Classification System / Front Occupant Classification Sensor LH Collision Detection (B1785)

DESCRIPTION

DTC B1785 is set when the occupant classification ECU receives a collision detection signal, which is sent by the front occupant detection sensor LH when an accident occurs.

DTC B1785 is also set when the front seat frame with adjuster RH is subjected to a strong impact, even if an actual accident has not occurred.

However, when the occupant classification ECU outputs a collision detection signal, even if the vehicle is not in a collision, DTC B1785 can be cleared by conducting the zero point calibration and sensitivity check.

Therefore, if DTC B1785 is set, first perform the zero point calibration and sensitivity check.

DTC Code

DTC Detection Condition

Trouble Area

B1785

Either of following conditions is met:

  • Occupant classification ECU receives collision detection signal, which is sent by front occupant detection sensor LH when accident occurs
  • Front seat frame with adjuster RH is subjected to strong impact, even if actual accident has not occurred
  • Front seat frame with adjuster RH (Front occupant detection sensor LH)
  • Occupant classification ECU

HINT:

  • When DTC B1650/32 is set as a result of troubleshooting the airbag system, perform troubleshooting for DTC B1785 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 ).

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 center airbag sensor (see page ).

(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 B1785 is not output.

HINT:

DTCs other than DTC B1785 may be output at this time, but they are not related to this check.

OK

USE SIMULATION METHOD TO CHECK

NG

2.

PERFORM ZERO POINT CALIBRATION

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

NG

GO TO STEP 5

OK

3.

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)

NG

GO TO STEP 5

OK

4.

CHECK FOR DTC

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

(b) Clear any DTCs stored in the center airbag sensor (see page ).

(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 B1785 is not output.

HINT:

DTCs other than DTC B1785 may be output at this time, but they are not related to this check.

OK

END

NG

5.

REPLACE FRONT SEAT FRAME WITH ADJUSTER ASSEMBLY RH

(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 front seat frame with adjuster RH (see page ).

HINT:

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

NEXT

6.

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 ).

NG

GO TO STEP 9

OK

7.

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)

NG

GO TO STEP 9

OK

8.

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 B1785 is not output.

HINT:

DTCs other than DTC B1785 may be output at this time, but they are not related to this check.

OK

END

NG

9.

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

10.

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

11.

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

    Rear Occupant Classification Sensor RH Circuit Malfunction (B1783)

    Front Occupant Classification Sensor RH Collision Detection (B1786)

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