What it means
The oxygen sensor pumping current trim circuit for bank 1 sensor 1 is above the expected level.
At a glance
- Usually lights the check-engine light
- Affects emissions; the car can fail an emissions test
How it works
The pumping-current trim circuit belongs to the upstream air-fuel sensor on bank 1, sensor 1, ahead of the catalytic converter on the cylinder 1 side. P2628 indicates that the module sees this trim circuit above its expected range; an open trim element or a wire contacting battery voltage can cause that condition. The affected sensor helps the module control bank 1 fueling.
Common causes
Most likely first.
- Open calibration trim resistor
- Corroded sensor connector
- Supply wire pinched against B+ source
Symptoms
- Check engine light on
- Increased fuel consumption
- Possible rough idle or hesitation
- Failed emissions test
How to diagnose it
- Review freeze-frame data and bank 1 sensor 1 readings to see whether the high trim-circuit fault coincides with abnormal fuel correction.
- Inspect the bank 1 sensor 1 connector and harness for corrosion, loose terminals, pinched insulation, or contact with a powered wire.
- Confirm the connector pins are seated and examine the sensor-side connection for corrosion that could interrupt the circuit.
- Use the wiring diagram to test the trim wire for a short to battery voltage and check continuity through the harness.
- Test the sensor's internal trim element according to the manufacturer's procedure for an open circuit.
- After repair, clear the fault and confirm the sensor data and fuel trims respond as expected.
Common fixes
- Repair a pinched trim wire that is contacting a powered source.
- Restore secure contact by repairing corroded or loose connector terminals.
- Replace damaged harness sections and secure them away from hot or powered components.
- Replace bank 1 sensor 1 if its internal trim element is open.
Can I keep driving?
You can usually drive gently if the engine remains smooth, but fuel economy and emissions may worsen and hesitation can develop. Limit unnecessary driving and address the fault before an emissions inspection.
A code shows where the control module detected a fault, not always which part failed. Check the causes in order and confirm with a test before replacing parts. Have several codes? Check them together
This is a generic code: it means the same on every make. The car’s maker may add more detail in its own service information.