P2503
Charging System Voltage Low
The ECU detects that battery voltage during operation stays below the regulated target. The alternator output is insufficient to maintain charge under load, eventually leading to battery depletion.
- Check engine light: Yes
- Emissions related: No
- Repair difficulty: medium
Common causes
Ordered by how often each turns out to be the cause.
- Weak alternator outputCommon
- Faulty voltage regulatorPossible
- Slipping drive beltLess likely
Parts involved
- Alternator
- Voltage Regulator
- Battery
- Drive Belt
P2503 is a generic OBD-II code defined by SAE J2012. Exact wording and diagnostic procedure vary by manufacturer and model. Code definitions are drawn from the public-domain OBDex dataset; the workshop notes are our own.