P2627
O2 Sensor Pumping Current Trim Circuit Low Bank 1 Sensor 1
On a wide-band (broadband) O2 sensor, the trim resistor circuit that calibrates the pumping current is reading low on bank 1 sensor 1. Air-fuel feedback gain is wrong, causing rich or lean offsets.
- Check engine light: Yes
- Emissions related: Yes
- Repair difficulty: medium
Symptoms
- Check engine light on
- Increased fuel consumption
- Possible rough idle or hesitation
- Failed emissions test
Common causes
Ordered by how often each turns out to be the cause.
- Short in the calibration trim resistorCommon
- Water intrusion in the sensor connectorPossible
- Connector pins corroded - high contact resistanceLess likely
Parts involved
- Oxygen Sensor Wideband B1s1
- Sensor Calibration Resistor
- Wiring Harness
P2627 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.