P0EF9Battery Charger A Input Voltage Sensor B Circuit Low
- Generic OBD-II code · Powertrain
- How the car detects it
- P0EF9 means the signal of input voltage sensor B in charger A has fallen below its valid range. No manufacturer documents P0EF9 publicly. GM's 2019 plug-in hybrid summary fails the matching sensor A code P0D3F when the duty cycle is 8 % or less but above zero, or stuck at 100 %, in at least 30 samples out of a window of 40 (Type B); a short to ground or a missing sensor supply produce that picture. Note that low refers to the measurement signal and not to a weak mains supply, which manufacturers report with input voltage too low codes such as P0D27. Because the charger cannot verify the incoming voltage, it does not begin AC charging. The high-side counterpart is P0EFA, the general circuit code P0EF7.
- What you may notice
- AC charging refused
- Charging fault message right after plugging in
- DC fast charging usually still possible
- Likely causes
- LikelyInternal fault of the charger measuring stage
- PossibleSensor signal shorted to ground
- PossibleMissing supply voltage of the sensing circuit
- Repair
- Workshop only · Usually a job for a workshop.Typical cost: €80 – €2,500
- Related codes
Explanation from obdex (CC0), exactly as the app shows it. Guidance only; confirm with a workshop.