P063A
Generator Voltage Sense Circuit A
Charging / electrical
Generic OBD-II
High
What it means
P063A means the ECM has a problem with the circuit it uses to sense the alternator/battery voltage. That sense signal is how the ECM decides how hard to make the alternator charge, so a fault can leave the system under- or over-charging — draining the battery or stressing electronics. It usually points to the sense wiring, a connection, or the alternator itself.
High
Can I keep driving? Risky — the ECM can't reliably sense charging voltage, so it may not regulate the alternator correctly. The battery can drain or overcharge, risking stalling. Have the charging system checked.
Common symptoms
What you'll notice
- Battery/charging warning light on
- Under- or over-charging (low or high system voltage)
- Dim or flickering lights and electrical glitches
- Discharged battery or, in severe cases, stalling
Common causes
Most likely first
- Damaged, open, or shorted generator voltage-sense wiringLikely
- Loose or corroded connection at the sense terminalCommon
- Failing alternator/generator or its regulatorCommon
- Weak battery skewing the referenceLess often
- ECM fault (checked last)Less often
How to diagnose & fix
Work through it in order
- Load-test the battery and measure charging voltage at idle (roughly 13.5–14.7V) to see how the system is behaving.
- Inspect the voltage-sense wire and connector between the alternator/battery and ECM for an open, short, or corrosion.
- Back-probe the sense circuit and compare the ECM reading to actual battery voltage.
- Repair the wiring or replace the alternator/generator as the test results dictate.
- Clear the code and re-test charging under load; suspect the ECM only if the circuit is good.
FAQ
Quick answers
Is it safe to drive with P063A?+
Only briefly. Without a good voltage-sense signal the charging system may not regulate, so the battery can drain or overcharge. Have it checked soon.
Can I just clear P063A?+
Clearing won't fix a broken sense circuit — it returns and the charging problem remains. Diagnose the wiring and alternator first.
Related codes
Often seen with P063A
Read & clear P063A 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