Powertrain, generic · Computer and auxiliary outputs

P063C Generator Voltage Sense Circuit A Low

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

Some charging systems measure the actual battery or alternator voltage through a separate sense line (regulator terminal S or an input of the module) to compensate voltage drops in the charging cable; without it the system reports a charging fault. No manufacturer document available to us uses P063A–P063D, so these descriptions follow the circuit principle and CARB, under which a charging-system input needs the check engine light only if it affects emissions or other diagnostics. P063C means the sense voltage is below its limit or below battery voltage – open circuit, short to ground or high resistance; the regulator may then overcharge or fall back to a fixed target.

Likely causes

Sense wire, fuse or connector between battery and alternator or module open or corroded
Alternator or regulator faulty
Contact resistance at battery terminals or grounds
Battery faulty

Symptoms

  • Battery warning lamp on
  • Charging voltage too high or too low (flat or overcharged battery)
  • Flickering lights
  • Further voltage codes (P0562/P0563)

Repair estimate

DifficultyMediumWorkshop job
Parts and labour€20–600
Time0.5–2.5 h

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

Parts involved

generator voltage sense circuitalternatorbattery

Related codes

P063AP063BP063DP0562P0563

References: law.cornell.edu, pmmonline.co.uk, hella.com.