P063B
Generator Voltage Sense Circuit A Range/Performance
Charging system
Generic OBD-II
High
What it means
P063B means the ECM's generator (alternator) voltage-sense circuit is reading outside its expected range, so the computer can't reliably monitor charging output. That points to the alternator's sense output, its wiring, or the connections — not to engine mechanicals. Left unaddressed it can cause over- or under-charging, which is hard on the battery and can eventually leave you stranded.
High
Can I keep driving? Drivable short-term but fix it soon — a faulty charging-voltage sense circuit can lead to over- or under-charging that damages the battery or leaves you stranded.
Common symptoms
What you'll notice
- Battery or charge warning light on
- Over-charging or under-charging (battery weak or overheating)
- Headlights brighter or dimmer than normal
- Check-engine light on
Common causes
Most likely first
- Faulty generator (alternator) or its voltage-sense outputLikely
- Open or shorted wiring in the generator voltage-sense circuitCommon
- Poor or corroded connection in the charging circuitCommon
- ECM fault (rare, on ECM-controlled charging systems)Less often
How to diagnose & fix
Work through it in order
- Measure charging voltage at the battery — compare with the ECM's sensed value on a scan tool to spot a bad sense signal.
- Inspect the generator sense wire and connectors for opens, shorts, or corrosion.
- Repair damaged wiring and connections in the charging circuit.
- Replace the alternator if its sense output or regulation is faulty, then clear and re-test.
FAQ
Quick answers
Is it safe to drive with P063B?+
For a short trip, yes, but don't ignore it. Incorrect charging can ruin the battery or leave the vehicle unable to restart, so get the charging system checked.
Can I just clear P063B?+
It returns while the sense circuit or generator is faulty. Fix the wiring or alternator first, then clear to confirm charging is correct.
Related codes
Often seen with P063B
Read & clear P063B yourself
Scan your car, confirm the code, and clear it once it's fixed — with OBD DashX on your phone.
✓ Verified name — SAE J2012 / ISO 15031-6Guidance reviewed by OBD DashX