P0AFB code meaning
Hybrid/EV Battery System Voltage High
Powertrain system Generic code P0Axx codes Check engine light
What P0AFB means
P0AFB guards against overcharging: the pack voltage, or a single cell, exceeds a temperature-dependent upper limit. GM's 2016 and 2019 tables use 320 of 400 samples (about 10 s) for the pack and 112 of 140 for a cell, Type A, and latch the code until a technician clears it by command; the 2011 Volt table also uses Type A. On the 2007-09 Saturn Vue Hybrid, GM's PIP4005A finds P0AFB together with P0AF8 caused by a loose negative battery cable. Mercedes-Benz uses P0AFB00 on 48 V starter-alternator systems for an on-board voltage that is too high, with software fixes for M256 engines, S-Class and GLE/GLS. Toyota's Prius Prime tech tip uses P0AFB11 with a current sensor text.
P0AFB at a glance
- Check engine lightYes, usually on
- Emissions testCan fail
- Limp modePossible
- Repair difficultyWorkshop only
- Typical labor0.5 to 8 hours
- Clears after repairWhen cleared with a scanner
Symptoms of P0AFB
- Hybrid system or MIL warning
- Start-stop or regenerative braking disabled
- Possible no crank on mild hybrids
Common causes of P0AFB
- PossibleLoose or arcing battery cable causing voltage spikes
- PossibleControl unit software allows overvoltage (Mercedes 48 V bulletins)
- PossibleCell imbalance so that one cell overcharges
- Less likelyFaulty voltage sensing reporting too high a value
Check the most likely causes first. Replacing parts by guesswork is the most expensive way to clear a code.
Parts involved
Hv batteryBms
What each part of P0AFB means
| P | Powertrain system: engine, fuel system, ignition, emissions and transmission. |
| 0 | Generic code: it means the same on every make (SAE standard). |
| A | Area: hybrid propulsion. |
| FB | The exact fault in that area. |
What to do next
- Note P0AFB 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 P0AFB
What does P0AFB mean?
P0AFB means "Hybrid/EV Battery System Voltage High". P0AFB guards against overcharging: the pack voltage, or a single cell, exceeds a temperature-dependent upper limit. It is a generic code, so it means the same on every make.
Is it safe to drive with P0AFB?
Drive gently and only to a workshop. With P0AFB the car can go into limp mode (reduced power) to protect itself.
Will P0AFB fail an emissions test?
Yes, it can. P0AFB is emissions-related, so most inspection programs fail a car while it is stored or while the check engine light is on.
How hard is P0AFB to fix?
Difficulty: workshop only. A typical repair takes 0.5 to 8 hours of work. This is a job for a workshop.
Will P0AFB clear itself after the repair?
Clear the code with a scanner after the repair. If the fault is fixed, it does not come back.