OBD-II reference

All 9.533 generic OBD-II codes, explained in detail.

Causes, inspection steps and sources — a comprehensive DIY archive. Created and maintained with love for the detail. Good luck and have fun!

Powertrain generic / SAE

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.

SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number5 / 03

Possible causes

  • Weak alternator output high
  • Faulty voltage regulator medium
  • Slipping drive belt low

Inspection / repair

  • Difficulty: medium
  • DIY: possible
  • Estimated cost: 150–800 €
  • Estimated time: 0.5–3 h
  • Component: alternator
  • Component: voltage regulator
  • Component: battery
  • Component: drive belt
  • MIL / check engine light

Sources

References

How to read OBD-II codes

The first letter names the vehicle system, the second digit distinguishes generic from manufacturer-specific, the remaining digits group fault area and number.

PPowertrain: engine, transmission, emissions
BBody: chassis trim, comfort, interior
CChassis: suspension, brakes, steering
UNetwork: CAN, control modules, communication