Toyota Tundra. Manual — part 2642

ASSEMBLY (for Column Shift Type) )

C: REPLACE CENTER AIRBAG SENSOR ASSEMBLY (See CENTER AIRBAG SENSOR
ASSEMBLY (for Floor Shift Type) )

A: END

DTC B1793: OCCUPANT CLASSIFICATION SENSOR POWER SUPPLY CIRCUIT
MALFUNCTION

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 TROUBLE DETECTION CONDITION TABLE

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

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

2009 Toyota Tundra

2009 RESTRAINTS Supplemental Restraint System - Tundra

Fig. 223: Identifying Occupant Classification Sensor Power Supply Circuit Malfunction - Wiring
Diagram
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

INSPECTION PROCEDURE

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.

1. CHECK FOR DTC

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

NOTE:

After the ignition switch is turned OFF, the navigation system requires
approximately 90 seconds to record various types of memory and settings. As a
result, after turning the ignition switch OFF, wait 90 seconds or more before
disconnecting the cable from the negative (-) battery terminal.

2009 Toyota Tundra

2009 RESTRAINTS Supplemental Restraint System - Tundra

b. Clear any DTCs stored in the memory (see DTC CHECK/CLEAR ).

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 ON, and wait for at least 60 seconds.

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

CHECK/CLEAR ).

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.

NG: Go to step 2

OK: USE SIMULATION METHOD TO CHECK (See DIAGNOSIS SYSTEM )

2. CHECK CONNECTION OF CONNECTOR

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 CONNECTOR

OK: Go to next step

3. CHECK CONNECTOR

a. Check that the connectors (on the occupant classification ECU side and the occupant detection

sensors side) are not damaged (see ELECTRONIC CIRCUIT INSPECTION PROCEDURE ).

OK: Connectors are not deformed or damaged.

NG: REPLACE FRONT SEAT WIRE RH

OK: Go to next step

2009 Toyota Tundra

2009 RESTRAINTS Supplemental Restraint System - Tundra

4. CHECK FRONT SEAT WIRE RH

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

sensors.

Fig. 224: Identifying Front Seat Wire RH
Courtesy of TOYOTA MOTOR SALES, U.S.A., INC.

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

c. Turn the ignition switch 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 SPECIFIED CONDITION TABLE

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

Standard Resistance

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

2009 Toyota Tundra

2009 RESTRAINTS Supplemental Restraint System - Tundra