Powertrain, generic · Hybrid propulsion

P0AFB Hybrid/EV Battery System Voltage High

Check engine lightOn
EmissionsRelevant
Drive cycleNot required
Limp modePossible

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.

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

Symptoms

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

Repair estimate

DifficultyShop_onlyWorkshop job
Parts and labour€100–6,000
Time0.5–8 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

hv batterybms

Related codes

P0AFAP0AF8P0AF9P0ABDP0BBE

References: gsi.ext.gm.com, gsi.ext.gm.com, static.nhtsa.gov, static.nhtsa.gov.