2001 Toyota PriusFACTORY OEM SERVICE PROCEDURE

HV Battery Control System: Pre-Check

  1. Precaution 
    1. To distinguish a trouble and replace a defective part, take necessary preventive measures against an electric shock. See GENERAL INFORMATION .
    2. Some portions of the wiring harness in the THS vehicle have the circuits, to which a high voltage is applied. To prevent an electrical shock, be sure to observe the following:
      1. Wear insulated gloves during inspection.
      2. Remove a service plug and do not start any repair operation before 5 minutes have passed, then confirm that the voltage at the output terminals has dropped down to 12 V or less.
      3. Use insulated tools during inspection.
      4. When disengaging wiring connectors, hold the connector bodies to avoid pulling the wires. When engaging wiring connectors, be sure to engage them securely.
    3. Do not leave tools or parts (bolts, nuts, etc.) inside the cabin.
    4. Do not carry metallic objects such as mechanical pencils or scales.
    Fig 1: Identifying Warning Lights
    G02805571Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  2. Diagnosis System 
    1. Description
      • The HV Battery ECU has a self-diagnosis system by which malfunction in the computer itself or in Hybrid System is detected and the master warning light in the combination meter and the Hybrid system warning light in the multi-information display lights up.
        Fig 2: Connecting Toyota Hand-Held Tester To Data Link Connector 3 (DLC3) On Vehicle
        G02805572Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      • To check the Diagnostic Trouble Codes (DTC), connect the TOYOTA hand-held tester to the Data Link Connector 3 (DLC3) on the vehicle. The TOYOTA hand-held tester also enables you to erase the DTC and check freeze frame data and various forms of THS data.
      • Freeze frame data:

        Freeze frame data records the battery condition when a malfunction is detected.

        When troubleshooting, this is useful for knowing the battery condition.

        Fig 3: Identifying DLC3 Connector Terminals
        G02805573Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      2. NOTE: If your display shows UNABLE TO CONNECT TO VEHICLE when you have connected the cable of the TOYOTA hand-held tester to the DLC3, turned the motor switch ON and operated the tester, there is a problem in the vehicle or tool.
      • 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, so consult the Service Department.
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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.

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