Code P2628 indicates that the powertrain control module (PCM) has detected a high voltage condition in the pumping current trim circuit of the upstream oxygen sensor (Bank 1, Sensor 1). This sensor is typically a wideband or air-fuel ratio sensor that uses a pumping current to accurately measure exhaust oxygen content. A high circuit reading usually points to an electrical fault within the sensor, its wiring, or the connected circuit.
The air-fuel ratio sensor itself has internally failed or shorted, causing the pumping current circuit to report a high voltage condition. This is the most common cause.
The wiring leading to the sensor may be chafed, melted, or shorted to voltage. Corroded or bent pins in the sensor connector can also disrupt the circuit.
A break in the specific wire carrying the pumping current signal between the oxygen sensor and the PCM, or a short to another wire, can trigger this code.
A poor or missing ground for the oxygen sensor circuit can cause electrical resistance to spike, leading to false high-voltage readings at the PCM.
The internal driver circuit inside the engine computer that monitors the pumping current has failed. This is extremely rare and should only be considered after all other components and wiring are verified.
The vehicle may still be drivable, but it can experience poor fuel economy, rough running, and will likely fail an emissions test. It is best to diagnose and repair the issue promptly to avoid potential catalyst damage.
No. Replacing the PCM is almost never the correct fix for this code. The oxygen sensor itself or a damaged wiring harness is the true cause in the vast majority of cases. The PCM should only be suspected after exhaustive electrical testing.
It is an electrical current used by wideband or air-fuel ratio sensors to precisely measure the exact amount of oxygen in the exhaust. Traditional sensors only toggle between rich and lean, while pumping current allows the sensor to provide an exact air-fuel ratio measurement.
Exhaust leaks usually cause codes related to sensor signal being stuck lean or slow response. Because P2628 specifies a 'circuit high' condition, it is primarily an electrical issue rather than an exhaust leak issue.