Toyota Tundra Service Manual: Diagnosis System

DIAGNOSIS SYSTEM

1. SYMPTOM SIMULATION

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.

(a) 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.

(b) 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.

2. FUNCTION OF PASSENGER AIRBAG ON/OFF INDICATOR

(a) Initial check

(1) Turn the ignition switch to ON.

(2) The passenger airbag ON/OFF indicator comes on for approximately 4 seconds, and then goes off for approximately 2 seconds.

(3) Approximately 6 seconds after the ignition switch is turned to ON, the passenger airbag ON/OFF indicator will indicate ON/OFF depending on the following conditions.

Indicator Operation

Front Passenger Seat Condition

Passenger Airbag ON/OFF Indicator

SRS Warning Light

ON Indicator

OFF Indicator

Vacant

Off

On

Off

Adult*1 is seated

On

Off

Off

Child*2 is seated

On or Off*2

Off or On*2

Off

Child restraint system is installed

Off

On

Off

Occupant classification system failure

Off

On

On

  • *1: The system judges a person of average adult weight or more as an adult. If a smaller adult sits in the front passenger seat, the system may not recognize them as an adult depending on their physique and posture.
  • *2: The system may not recognize a child or a child in a child restrain system as a child depending on factors such as the positioning of the child restraint system or the child's physique or posture.

HINT:

  • The timing chart below shows the operation of the passenger airbag ON/OFF indicator. Use the chart to check the indicator light circuit.
  • When the occupant classification system has trouble, both the SRS warning light and passenger airbag ON/OFF indicator ("OFF") come on. In this case, check for DTCs for "Airbag System" first. Then troubleshoot the occupant classification system if DTC B1650 is output, and troubleshoot the passenger airbag ON/OFF indicator if DTC B1660 is output.

3. CHECK PASSENGER AIRBAG ON/OFF INDICATOR

(a) Turn the ignition switch to ON.

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

HINT:

In order to check the operation of the passenger airbag ON/OFF indicator when approximately 6 seconds have elapsed after turning the ignition switch to ON, refer to the table in the previous step.

    Data List / Active Test

    Diagnostic Trouble Code Chart

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