P0EF9 code meaning
Battery Charger A Input Voltage Sensor B Circuit Low
What P0EF9 means
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.
P0EF9 at a glance
- Check engine lightUsually not
- Emissions testNot an emissions code
- Limp modeNot expected
- Repair difficultyWorkshop only
- Typical labor0.5 to 4 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P0EF9
- AC charging refused
- Charging fault message right after plugging in
- DC fast charging usually still possible
Common causes of P0EF9
- Most likelyInternal fault of the charger measuring stage
- PossibleSensor signal shorted to ground
- PossibleMissing supply voltage of the sensing circuit
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Battery charger a input voltage sensor bWiring harnessOn board charger
What each part of P0EF9 means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| F9 | The exact fault in that area. |
What to do next
- Note P0EF9 and any other codes stored with it: several codes together often point to one cause.
- Check for loose connectors and damaged wiring around the parts the code names.
- Check open recalls for your car: some faults are fixed for free by the dealer. Enter your VIN.
- Clear the code only after the repair. If it comes back, the fault is still there.
Buying a used car? Scan it for stored codes before you pay. A recently cleared memory can hide a problem.
Questions about P0EF9
What does P0EF9 mean?
P0EF9 means "Battery Charger A Input Voltage Sensor B Circuit Low". P0EF9 means the signal of input voltage sensor B in charger A has fallen below its valid range. It is a generic code, so it means the same on every make.
Is it safe to drive with P0EF9?
P0EF9 does not normally turn on the check engine light by itself. Watch for the symptoms above and have it checked soon.
Will P0EF9 fail an emissions test?
P0EF9 is not an emissions code, so on its own it usually does not fail an emissions test. Other stored codes or a lit check engine light still can.
How hard is P0EF9 to fix?
Difficulty: workshop only. A typical repair takes 0.5 to 4 hours of work. This is a job for a workshop.
Will P0EF9 clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.