The P0051 code indicates that the engine control module has detected a low-voltage or low-resistance condition in the heating circuit of the oxygen sensor located on Bank 2, Sensor 1. This heater is designed to bring the sensor up to operating temperature quickly to ensure accurate emissions readings during cold starts.
The internal heating element within the oxygen sensor has suffered an internal short or failure.
The heater circuit wires are frayed, melted, or shorted to the chassis or another wire.
Moisture or contaminants in the sensor connector have caused high resistance or a short circuit.
A fuse protecting the oxygen sensor heater circuit has blown, interrupting power delivery.
An internal failure in the engine control module's heater driver circuit.
Not necessarily. The sensing element may still function, but the heater element has failed, which prevents the sensor from working correctly until it is naturally heated by exhaust gases.
It is highly unlikely that the PCM is the cause. P0051 is almost always caused by the sensor itself or the associated wiring; replacing the PCM without first verifying the sensor and harness is generally incorrect.
Yes, the vehicle will remain drivable, but it will operate in open-loop mode longer than intended, increasing emissions and reducing efficiency until the sensor reaches operating temperature.