P0064 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2, Sensor 3)

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P0064 trouble code definition

Indicates that there is an abnormally high voltage or resistance present in the heater control circuit of oxygen sensor (bank 2 sensor 3). The oxygen sensor measurements only become accurate when the sensor reaches a temperature of 600 degrees or above.

The power control module (PCM) sends a voltage to the heater circuit of the oxygen sensor. The sensor will then turn most of that voltage into heat, but will also use the voltage as a way to communicate the air-fuel ratio to the power control module.

The voltages and resistances being produced by the oxygen sensor must be within a certain specification or the power control module will try to adjust the air-fuel ratio. The high voltage or resistance output of oxygen sensor usually indicates that there is a rich air-fuel ratio being detected.

What the P0064 code means

It will usually mean that a rich air-fuel ratio is being detected. The computer of the vehicle (PCM) will then attempt to correct the air-fuel ratio by decreasing the amount of fuel the engine receives.

The PCM will regulate the air-fuel ratio and attempt to keep it at or near the stoichiometric range of 14.7:1. The stoichiometric range is ideal because it regulates the consumption of fuel, and limits the amount of harmful pollutants that an engine will produce.

What causes the P0064 code?

  • A bad oxygen sensor
  • Excessive soot or carbon buildup on the oxygen sensor, restricting it from measuring an accurate reading
  • Contaminated electrical connections or wiring
  • Shorted or open circuit conditions
  • A dirty or faulty mass airflow sensor

What are the symptoms of the P0064 code?

  • Loss of engine power and performance
  • A service engine light or Check Engine Light soon becoming displayed
  • A darker than normal exhaust smoke
  • A rich smell of gas from the exhaust

How does a mechanic diagnose the P0064 code?

  • Measuring the resistance output and voltage signal of the oxygen sensor by the use of a scan tool or multimeter, then comparing it to the manufacture specifications

  • Inspecting the base of the oxygen sensor for excessive soot or carbon buildup

  • By checking the electrical terminals and wiring for damage, corrosion, and other contaminants

Common mistakes when diagnosing the P0064 code

  • Replacing the wrong sensor by misinterpreting the order of the two to five oxygen sensors

  • Failing to clean or check the condition of the mass air flow sensor

How serious is the P0064 code?

  • It is very harmful to the environment because the engine won’t be able to accurately limit the amount of pollutants it creates.

  • Running a rich air-fuel ratio will shorten the lifespan of the catalytic convertor.

  • This code will shorten the life of engine components, such as the spark plugs.

What repairs can fix the P0064 code?

Additional comments for consideration regarding the P0064 code?

Check the condition of the spark plugs when diagnosing this trouble code. The condition of the spark plugs will help determine if the vehicle is in fact running rich. When a engine runs rich the spark plugs will likely have excessive soot and carbon build up or a strong fuel odor.

Need help with a P0064 code?

YourMechanic offers certified mobile mechanics who will come to your home or office to diagnose and repair your vehicle. Get a quote and book an appointment online or speak to a service advisor at 1-800-701-6230.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

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