OBDII Code List

P0031 2005 TOYOTA PRIUS - Oxygen Sensor Heater Control Circuit Low Bank 1 Sensor 1

Repair Importance Level: 2/3
Repair Difficulty Level: 2/3   
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Possible causes

  • Faulty Air-Fuel Ratio (A/F) Sensor Bank 1 Sensor 1
  • Air-Fuel Ratio (A/F) Sensor Bank 1 Sensor 1 harness is open shorted to ground
  • Air-Fuel Ratio (A/F) Sensor Bank 1 Sensor 1 circuit poor electrical connection
  • EFI relay (integration relay)
  • Faulty Engine Control Module (ECM)
  • Tech notes

    Check EFI relay (integration relay) before checking or replacing the oxygen sensor.

    When is the code detected?

    The P0031 is set when the ECM detects an excessively low voltage through the heated oxygen sensor heater circuit

    Possible symptoms

  • Engine Light ON (or Service Engine Soon Warning Light)
  • P0031 2005 Toyota Prius Description

    Air-Fuel Ratio (A/F)sensor need to reach a minimum operating temperature of 1200 degrees F to produce an accurate voltage signal. The faster the air-fuel ratio sensor reaches that temperature the faster the sensor will start sending an accurate signal to the Engine Control Module (ECM).

    In order to achieve the require temperature, a heater element is included inside the air-fuel ratio sensor. The ECM controls the air-fuel ratio sensor heater element based on signals from the engine coolant temperature and engine load. The ECM controls the heater element circuit by allowing current flow to ground.

    The ECM monitors the voltage signal received through the heater element circuit and determines the state of the circuit by comparing the voltage detected with the factory specifications.

    OBDII Code P0031 2005 Toyota Prius - Oxygen Sensor Heater Control Circuit Low Bank 1 Sensor 1 -

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