P0064 is set when the PCM detects a higher‑than‑expected voltage in the heater control circuit of the heated oxygen sensor located after the catalytic converter on Bank 2 (sensor 3). This usually means the heater is staying on or is being forced to a high‑voltage state, which can affect fuel‑mixture control and increase emissions. The malfunction indicator lamp (MIL) will illuminate and the vehicle may run slightly richer or exhibit poorer fuel economy.
The heater inside the sensor can short internally, causing the PCM to see a high voltage condition in the control circuit.
Chafed, melted, or corroded wires can create a short to battery voltage or an open ground, leading to an abnormal voltage reading.
If the fuse that supplies power to the heater element blows, the circuit may exhibit abnormal voltage levels, triggering the code.
Oxidation at the ground pin can cause the circuit to read high voltage because the ground reference is lost.
In very few cases the PCM itself may malfunction and incorrectly command the heater circuit, but this should be ruled out after checking the sensor and wiring.
No. The most common cause is a failed heater inside the oxygen sensor or a wiring problem. PCM replacement is rarely needed and should only be considered after all other potential causes have been eliminated.
The vehicle can still be driven, but you may notice higher emissions and reduced fuel economy. In regions with emissions testing, a P0064 will usually cause a failure.
Using a multimeter, measure the resistance between the heater pins on the sensor. A reading that is far outside the specification (usually a few ohms) or an open circuit indicates a faulty heater.
Yes. If the fuse that protects the heater circuit is blown, the PCM may see an abnormal voltage condition. Always check the fuse and relay before replacing the sensor.