Diagnosis System

HINT:

The most difficult case in troubleshooting is when no problem symptoms occur. In such a case, a thorough problem analysis must be carried out. A simulation of the same or similar conditions and environment in which the problem occurred in the customer's vehicle should be carried out. No matter how much skill or experience a technician has, troubleshooting without confirming the problem symptoms will lead to important repairs being overlooked and mistakes or delays.

1. Vibration method: When vibration seems to be the major cause.

   HINT:

   Perform the simulation method only during the primary check period (for approximately 6 seconds after the ignition switch is turned ON).

   1. Slightly vibrate the part of the sensor considered to be the cause of the problem with your fingers and check whether the malfunction occurs.

      HINT:

      Shaking the relays too strongly may result in open relays.

   2. Slightly shake the connector vertically and horizontally.
   3. Slightly shake the wire harness vertically and horizontally.

      The connector joint and fulcrum of the vibration are the major areas to be checked thoroughly.

2. Simulation method for DTC B1795: Turn the ignition switch from OFF to ON, hold it for 10 seconds, and then turn it back to OFF. Repeat this procedure 50 times in a row.

   HINT:

   DTC B1795 is output if the occupant classification ECU receives the ignition switch lock-on-lock signal 50 times in a row when a malfunction occurs in the power circuit for the occupant classification system.

   Fig 1: Identifying Vibration Method

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

1. Initial check
   1. Turn the ignition switch ON.
   2. The passenger airbag ON/OFF indicator (ON and OFF) comes on for approximately 4 seconds, then goes off for approximately 2 seconds.
   3. Approximately 6 seconds after the ignition switch is turned ON, the passenger airbag ON/ OFF indicator will be ON/OFF depending on the conditions listed below.

      except Double Cab: 

      INDICATOR CONDITION TABLE
      
      

      Front Seat Passenger	ON Indicator	OFF Indicator	SRS Warning Light
      Adult seated	ON	OFF	OFF
      Child seated/Child restraint system set	OFF	ON	OFF
      Vacant	OFF	OFF	OFF
      Passenger occupant classification system failure	OFF	ON	ON

      for Double Cab: 

      PASSENGER AIRBAG CUTOFF SWITCH POSITION TABLE
      
      

      Front Seat Passenger	Passenger Airbag Cutoff Switch Position	ON Indicator	OFF Indicator	SRS Warning Light
      Adult seated	ON	ON	OFF	OFF
      	OFF	OFF	ON	OFF
      	Passenger airbag cut-off switch system failure	OFF	ON	ON
      Child seated/Child restraint system set	ON	OFF	ON	OFF
      	OFF	OFF	ON	OFF
      	Passenger airbag cut-off switch system failure	OFF	ON	ON
      Vacant	ON	OFF	OFF	OFF
      	OFF	OFF	ON	OFF
      	Passenger airbag cut-off switch system failure	OFF	ON	ON
      Passenger occupant classification system failure	ON	OFF	ON	ON
      	OFF	OFF	ON	ON
      	Passenger airbag cut-off switch system failure	OFF	ON	ON

      HINT:

      • The passenger airbag ON/OFF indicator operates based on the timing table below in order to check the indicator light circuit.
        Fig 2: Identifying Passenger Airbag ON/OFF Indicator Flash-Pattern

        Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      • When the occupant classification system has trouble, both the SRS warning light and the passenger airbag ON/OFF indicator (OFF) come on. In this case, check the DTCs in the airbag system first.

1. Turn the ignition switch ON.
2. Check that the passenger airbag ON/OFF indicator (ON and OFF) comes on for approximately 4 seconds, then goes off for approximately 2 seconds.

   HINT:

   Refer to the table in the previous step regarding the passenger airbag ON/OFF indicator when approximately 6 seconds have elapsed after the ignition switch is turned ON.