P2250 means the powertrain control module has detected a higher-than-expected voltage on the reference voltage circuit for the upstream oxygen sensor on bank 2. This reference voltage is used by the PCM to bias or monitor the oxygen sensor signal, so a 'high' reading indicates an electrical fault rather than a simple rich exhaust condition. The problem is usually a short to voltage in the wiring, a failed sensor, or a connector issue.
The reference voltage wire may be chafed, pinched, or melted and touching a battery-voltage source, pulling the circuit high. This is the most common cause of a 'circuit high' oxygen sensor code.
An internal short or failure inside the upstream oxygen sensor can pull the reference voltage high. If the harness tests good, the sensor itself should be suspected.
Moisture, corrosion, bent pins, or poor terminal tension in the O2 sensor connector can create stray voltage paths or high resistance that raises the reference circuit voltage.
If the wiring, connector, and sensor are all verified good and the PCM still outputs or reads a high reference voltage, the control module may be at fault. This is uncommon.
Short trips are usually possible, but the code can hurt fuel economy and emissions control. It should be diagnosed promptly to avoid added stress on the catalytic converter or a failed emissions test.
No. The PCM is rarely the cause. Most P2250 codes are due to wiring shorts, connector problems, or a failed oxygen sensor. Consider the PCM only after the circuit and sensor are proven good.
Bank 2 Sensor 1 is the upstream, pre-catalytic converter oxygen sensor on the cylinder bank that does not contain cylinder number one.
A faulty oxygen sensor can cause P2250 if it has an internal short that pulls the reference voltage high. Wiring shorts are at least as common, so both the harness and the sensor should be tested.