P2255 indicates the powertrain control module (PCM) has detected a voltage signal below the expected range in the negative current control circuit for the Bank 2 Sensor 1 oxygen (air-fuel ratio) sensor. This circuit regulates the pump current that maintains the sensor's internal reference voltage, and a low signal typically points to an open circuit, high resistance, or sensor internal failure.
Internal open or high resistance in the sensor's negative current control circuit is the most common cause.
Open circuit, corrosion, damaged pins, or chafed wires between the PCM and sensor connector.
A blown fuse supplying voltage to the sensor's heater or control circuits can create a low-signal condition.
An upstream leak can allow outside air to reach the sensor, skewing its operation and triggering circuit codes.
Internal PCM fault in the negative current driver is possible but rare; verify wiring and sensor first.
No. PCM failure is uncommon; the sensor itself or its wiring is responsible in the vast majority of cases.
Yes. A leak upstream of Bank 2 Sensor 1 can affect sensor operation and set circuit-related codes.
Not required. Replace only the sensor indicated by the code unless diagnostics show both are degraded.
Clearing only turns off the light. The code will return if the underlying circuit or sensor fault is not repaired.