P0AF8 compares the battery pack voltage reported by the battery controller with an independent measurement on the high-voltage bus. GM calls it system voltage correlation: with the contactors closed, the 2019 tables fail it when the pack reading differs from the inverter bus voltage by more than 13.95 V, or from the charger bus voltage by more than 14.95 V, 400 of 500 samples at 25 ms, Type A. The 2011 Volt table uses 12 V and Type A, the 2013 eAssist table 5.77 V against the motor controller, Type B. GM's Saturn Vue Hybrid PIP4005A links P0AF8 with P0AFB to a loose negative battery cable, and Volt PIC6089B mentions it with low 12 V system faults. P0AFA and P0AFB judge the voltage level itself.
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
- MIL and hybrid or EV warning on
- Battery saver or low battery message
- Intermittent no crank or reduced hybrid power
Most likely causes
- Loose or arcing high-voltage battery cable connection
- Pack or bus voltage sensing circuit inaccurate
- Low 12 V supply or loose 12 V power fuse affecting the measuring modules
- High resistance in a pack fuse or main contactor
What to check, in order
Start with the simplest. You can tick off each step.
Good to know
- It can trigger limp mode.
- It affects emissions.
What each character of P0AF8 means
- P: Powertrain: engine and transmission
- 0: Generic code: same on every make
- A: Hybrid or air and fuel
- F8: Specific fault in that system
Frequently asked questions
Can I keep driving with code P0AF8?
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 P0AF8?
The most common causes are: loose or arcing high-voltage battery cable connection; pack or bus voltage sensing circuit inaccurate; low 12 V supply or loose 12 V power fuse affecting the measuring modules.
Related codes
- P0AFAHybrid/EV Battery System Voltage Low
- P0AFBHybrid/EV Battery System Voltage High
- P0AF9Hybrid/EV Battery System Voltage Unstable
- P0ABBHybrid/EV Battery Pack Voltage Sense A Circuit Range/Performance
- P0ABCHybrid/EV Battery Pack Voltage Sense A Circuit Low
- P0ABDHybrid/EV Battery Pack Voltage Sense A Circuit High
Sources
- gsi.ext.gm.com: 19OBDG01 Hybrid Diagnostics
- gsi.ext.gm.com: 13OBDG05C Hybrid Diagnostics
- gsi.ext.gm.com: 11OBDG01 HYBRID Diagnostics
- static.nhtsa.gov: MC 10154281 9999
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.