P2627: O2 Sensor Pumping Current Trim Circuit Low Bank 1 Sensor 1
What to do
The car will generally drive normally with slightly worse fuel consumption, and the emissions monitors will not complete.
Ask for the whole sensor loom to be inspected rather than just the one circuit. These sensors carry several wires together from a hot exhaust component, so damage that affects one has usually affected its neighbours — and repairing a single conductor in a loom that has chafed means the fault returns in a different form. The warnings at P2626 about testing and about connector repairs apply here too.
What this code means
The pumping current trim circuit reads below its valid range on the bank 1 upstream sensor — normally a short to ground. What the trim circuit does, and why an uncalibrated wideband sensor is worse than no sensor, is at P2626.
A short to ground on this circuit is worth checking against the sensor's other conductors rather than in isolation. These sensors carry several wires in one small loom — pump cell, reference, trim and a heater drawing real current — running from a hot exhaust component to the module. A chafe that grounds the trim line has almost certainly damaged its neighbours, and the heater conductor is the one that matters, because a heater fault produces its own codes and its own consequences. Repairing one conductor in a loom that has rubbed through is a repair that comes back.
Likely causes
Start here
- Wiring shorted to ground · moderate
- Damaged wiring harness · moderate
- Faulty oxygen sensor · moderate
Less common
- Heat damage to sensor or wiring · moderate
- Corroded or loose connector · easy
Symptoms
Components involved
Information, not instruction
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Have anything you intend to act on checked by a trained person against the manufacturer's own procedure for your vehicle. Nothing here replaces that procedure.
Community experience
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