P0AFB: Hybrid/EV Battery System Voltage High

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.

High severity. Can I keep driving?If the car still runs, drive as little as possible and go to a specialized repair shop. Do not touch the orange cables: they carry high voltage.

Symptoms

Hybrid system or MIL warning
Start-stop or regenerative braking disabled
Possible no crank on mild hybrids

Most likely causes

Loose or arcing battery cable causing voltage spikes
Control unit software allows overvoltage (Mercedes 48 V bulletins)
Cell imbalance so that one cell overcharges
Faulty voltage sensing reporting too high a value

What to check, in order

Start with the simplest. You can tick off each step.

Read the codes with a hybrid-compatible scanner and write down the freeze frame data
Check the sensor's ground and make sure the signal wire is not receiving voltage from another circuit.
Make sure the battery cooling air intake is clean
Check the 12 V auxiliary battery, which can also trigger warnings
Leave any high-voltage measurements to a specialized repair shop

Good to know

It can trigger limp mode.
It affects emissions.

What each character of P0AFB means

P: Powertrain: engine and transmission
0: Generic code: same on every make
A: Hybrid or air and fuel
FB: Specific fault in that system

Frequently asked questions

Can I keep driving with code P0AFB?

If the car still runs, drive as little as possible and go to a specialized repair shop. Do not touch the orange cables: they carry high voltage.

What causes code P0AFB?

The most common causes are: loose or arcing battery cable causing voltage spikes; control unit software allows overvoltage (Mercedes 48 V bulletins); cell imbalance so that one cell overcharges.

Related codes

Sources

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.