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(a) To distinguish a trouble and replace a defective part, take necessary preventive measures against an electric shock (See page IN-4).

(b) 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:

Wear insulated gloves during inspection. 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. Use insulated tools during inspection. When disengaging wiring connectors, hold the connector bodies to avoid pulling the wires. When engaging wiring connectors, be sure to engage them securely.

(c) Do not leave tools or parts (bolts, nuts, etc.) inside the cabin.

(d) Do not carry metallic objects such as mechanical pencils or scales.

Toyota Prius Master Warning Light


(a) 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.

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.

Precheck 2003 Toyota PriusCorolla E11 Data Link

The HV control ECU conforms to ISO 14230 for communication.

The terminal arrangement of the DLC3 complies with SAEJ1962 and matches the ISO 14230 format.

Terminal No.

Connection/Voltage or Resistance



Bus ® Line/Pulse generation

During transmission


Chassis Ground ^ Body Ground/1 Q or less



Signal Ground ^ Body Ground/1 Q or less



Battery Positive ^ Body Ground/10 - 15 V

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.

3. INSPECT DIAGNOSIS (a) Check the auxiliary battery.

(1) Measure the voltage of the auxiliary battery. Voltage: 10 - 15 V

Precheck 2003 Toyota Prius

(2) Inspect the auxiliary battery, fuses, fusible links, wiring harness, connectors and ground. (b) Check the master warning light.

(1) Turn the ignition switch ON and confirm that the master warning light comes on.


If the master warning light does not come on, suspect a burnt fuse, burnt bulb, or open in wiring harness.

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