Electronic Circuit Inspection Procedure

BASIC INSPECTION
1. RESISTANCE MEASURING CONDITION OF ELECTRONIC PARTS
  1. Unless stated, all resistance is measured at an ambient temperature of 20°C (68°F). Because the resistance may be outside the specifications if measured at high temperatures immediately after the vehicle has been running, measurements should be made when the engine has cooled down.
    
    Fig 1: Identifying Correct And Wrong Position For Connecting Connectors
    Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
2. HANDLING OF CONNECTOR
  1. When removing the connector with a lock, press the connector toward the engagement and remove the lock by making the lock claw movable easily.
  2. When removing the connector, do not hold the harness, but hold the connector.
  3. Before connecting the connector, check that there are no deformation, damage and missing of the terminals.
  4. Connection of the connector with a lock should be securely done until it makes a click sound.
  5. In case of checking the connector with a Toyota electrical tester, perform it at the back side (harness side) of the connector using a mini test lead.
  NOTE:
  - As a water proof connector cannot be checked from its back side, check by connecting the sub-harness.
  - Do not damage the terminals by moving the inserted tester needle.
3. CONNECTOR CHECKING POINTS
  1. Checking when the connector is connected: By holding the connector, check the inserted condition and locking efficiency (engaged condition).
  2. Checking when the connector is removed: Check by pulling the wire harness lightly (missing terminal, terminal crimping condition, core wire break).
    Check visually if there is any rust, metal tip, water and bend of terminal (rust, mixing of foreign object, terminal deformation).
    
    NOTE: When testing a gold-plated female terminal, always use a gold-plated male terminal.
    
    Fig 2: Checking Connectors
    Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  3. Checking of the contact pressure of the terminal: Prepare the same terminal as a male terminal.
    By inserting it to a female terminal, check the engaged condition and sliding load.
    
    Fig 3: Inserting Male Terminal Into Female Terminal
    Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
4. REPAIR METHOD OF CONNECTOR TERMINAL
  1. In case that there is any soil at the contact point, clean the contact point using an air gun or shop rag. At this time, never polish the contact point using a sand paper as the plating may come off.
  2. In case of abnormal contact pressure, replace the female terminal. At this time, if a male terminal is gold-plated (gold color), use gold-plated female terminals and if it is silver-plated (silver color), use silver-plated female terminals.
5. HANDLING OF WIRE HARNESS
  
  Fig 4: Identifying Correct And Wrong Procedure While Repairing Connector
  Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  1. In case of removing the wire harness, check the wiring and clamping condition before the work so as to restore it correctly.
  2. Never twist, pull or slack off the wire harness more than necessary.
  3. Never make the wire harness come into contact with a high-temperature part, rotating, moving, vibrating or acute-angled part (edge of the panel, tip of the screw, etc.).
  4. When installing parts, never sandwich the wire harness between them.
  5. Never cut or break the cover of the wire harness. If it is cut or broken, replace it or securely repair it with a vinyl tape.
    
    Fig 5: Identifying Wrong Position Of Wire Harness
    Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
CHECK OPEN CIRCUIT
CHECK SHORT CIRCUIT
CHECK AND REPLACE ECU
NOTE:
- Start an inspection of the connector from the backside of the connector at the wire harness side with the connector connected to the ECU.
- When no measuring condition is specified, perform the inspection with the engine stopped and also the ignition switched ON.
1. First check the ECU ground circuit. If it is faulty, repair it. If it is normal, the ECU could be faulty. So, replace the ECU with a normal functioning one and check if the symptoms appear.
  1. Measure the resistance between the ECU ground terminal and body ground.
    Resistance: 1 Ω or less
    
    Fig 6: Measuring Resistance Between ECU Ground Terminal And Body Ground
    Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  2. Disconnect the ECU connector, check the ground terminals on the ECU side and wire harness side for bend and check the contact pressure.
    
    Fig 7: Disconnecting ECU Connectors
    Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002