Diagnosis System

1. Check the DLC3.
   1. The vehicle's ECM conforms to ISO 9141-2 for communication protocol. The terminals arrangement of the DLC3 complies with SAE J1962 and meets the ISO 9141-2 format.
      Fig 1: Identifying DLC3 Connector Terminals

      Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      DLC3 CONNECTOR TERMINALS REFERENCE CHART
      
      

      Terminal No.	Connection Voltage or Resistance	Condition
      7	Bus + Line/Pulse generation	During Transmission
      4	Chassis Ground - Body Ground/Below 1 Ω	Always
      16	Battery Positive - Body Ground/10 to 14 V	Always

      HINT:

      If the display shows UNABLE TO CONNECT TO VEHICLE when connecting the cable of the hand-held tester to the DLC3, turning the ignition switch to the ON position and operating the hand-held tester, there is a problem on the vehicle side or tool side.

• If communication is normal when the tool is connected to another vehicle, inspect the DLC3 on the original vehicle.
• If communication is still not possible when the tool is connected to another vehicle, the problem is probably in the tool itself. Consult the Service Department listed in the tool's instruction manual.

HINT:

The most difficult case in troubleshooting is when no symptoms occur. In such cases, a thorough customer problem analysis must be carried out. Then the same or similar conditions and environment in which the problem occurred in the customer's vehicle should be simulated. No matter how experienced or skilled a technician may be, if he proceeds to troubleshoot without confirming the problem symptoms, he will likely overlook something important and make a wrong guess at some points in the repair operation.

This leads to a standstill in troubleshooting.

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 to the ON position).

   1. Slightly vibrate the part of the sensor considered to be the problem cause 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: Repeat turning the ignition switch from the LOCK to ON position 50 times in a row (LOCK to ON to LOCK should be counted as 1 time).

   HINT:

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

   Fig 2: Identifying Vibration Method

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

1. Primary check.
   1. Turn the ignition switch to the LOCK position. After 2 seconds or more, turn the ignition switch to the ON position. The SRS warning light comes on for approximately 6 seconds and the diagnosis of the SRS airbag system (including the seat belt pretensioner and front passenger occupant classification system) is performed.

      HINT:

      If a trouble is detected during the primary check, the SRS warning light remains on or blinks even after the primary check period (for approximately 6 seconds) has elapsed.

2. Constant check.
   1. After the primary check, the airbag sensor assy center takes effect the SRS airbag system and monitors it for trouble constantly.

   HINT:

   If trouble is detected during the constant check, the airbag sensor assy center functions as follows.

   • The SRS warning light comes on or blinks.
   • The SRS warning light comes on, and then goes off. This blinking pattern indicates the source voltage drop. The SRS warning light goes off 10 seconds after the source voltage returns to normal.
3. Review.
   1. When the airbag system is normal;

      The SRS warning light comes on only for the primary check period (for approximately 6 seconds after the ignition switch is turned to the ON position).

   2. When the airbag system has trouble;
      • The SRS warning light remains on or blinks even after the primary check period has elapsed.
      • The SRS warning light goes off after the primary check, but comes on or blinks again during the constant check.
      • The SRS warning light does not come on when turning the ignition switch from the LOCK to ON position.

   HINT:

   The airbag sensor assy center keeps the SRS warning light ON if the airbag has been deployed.

1. (3) Turn the ignition switch to the ON position, and check that the SRS warning light comes on for approximately 6 seconds (primary check).
2. (4) Check that the SRS warning light goes off approximately 6 seconds after the ignition switch is turned to the ON position (constant check).

HINT:

When any of the following symptom occurs, refer to the PROBLEM SYMPTOMS TABLE  .

• When the SRS warning light comes on occasionally even after the primary check period has elapsed, an open or short in the SRS warning light circuit is suspected.
• When the SRS warning light comes on even when the ignition switch is in the LOCK position, trouble in the power source or combination meter assy is suspected.
• When the ignition switch is turned from the LOCK to ON position, the SRS warning light does not come on.
  Fig 3: Checking SRS Warning Light

  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

1. Initial check.
   1. Turn the ignition switch to the ON position.
   2. The passenger airbag ON/OFF indicator comes on for approximately 4 seconds, then goes off for approximately 2 seconds.
   3. Approximately 6 seconds after the ignition switch is turned to the ON position, the passenger airbag ON/OFF indicator will be ON/OFF depending on the conditions listed below.
      Fig 4: Identifying Function Of Passenger Airbag On/Off Indicator

      Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      Fig 5: Passenger Airbag Reference

      Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

HINT:

• The passenger airbag ON/OFF indicator is based on the timing chart below in order to check the indicator light circuit.
  Fig 6: Timing Chart - Indicator Light Circuit

  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
• When the front passenger occupant classification system has trouble, both the SRS warning light and the passenger airbag ON/OFF indicator comes on. In this case, check the DTCs in the supplemental restraint system first. Then troubleshoot the front passenger occupant classification system if DTC B1150/23 is indicated and troubleshoot the passenger airbag ON/OFF indicator if DTC B1152/28 is detected.

1. The activation prevention mechanism is built into the connector for the squib circuit of the SRS. As explained later, during troubleshooting, insert a piece of paper with the same thickness as the male terminal between the terminal and the short spring to release it.