P063D
Generator Voltage Sense Circuit A High
Charging system
Generic OBD-II
High
What it means
P063D means the ECM sees an abnormally high reading on the generator (alternator) voltage-sense circuit it uses to regulate charging. With a bad feedback signal the ECM can command the wrong charging output, leading to an under- or over-charged battery, warning lights, and dim or flickering lights. It's worth diagnosing before the battery is left flat.
High
Can I keep driving? Have it checked soon — a charging-feedback fault can lead to under- or over-charging, a dead battery, or electrical problems on the road.
Common symptoms
What you'll notice
- Battery or charging-system warning light on
- Check-engine light on
- Battery undercharged, or dim/flickering lights
- Hard starting from a low battery
Common causes
Most likely first
- Short to voltage or open in the generator voltage-sense circuitLikely
- Poor connections or grounds in the charging circuitCommon
- Faulty generator (alternator) or its voltage regulatorCommon
- ECM fault (rare)Less often
How to diagnose & fix
Work through it in order
- Test battery condition and measure charging voltage at idle and under load.
- Inspect the generator voltage-sense wiring and connectors for damage or a short to voltage.
- Check the charging-system grounds and the alternator connections.
- Test the alternator/regulator output; replace the alternator if it can't regulate correctly.
- If wiring and alternator are good, have the ECM circuit tested. Clear and re-test.
FAQ
Quick answers
Is it safe to drive with P063D?+
Only briefly. If the charging system isn't regulating correctly the battery can drain or overcharge, so get it diagnosed before longer trips.
Can I just clear P063D?+
It will return while the sense circuit reads high. Repair the wiring or alternator first, then clear it.
Related codes
Often seen with P063D
Read & clear P063D 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