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

P2509

ECM/PCM Power Input Signal Intermittent

The ECU detects sporadic interruptions of its supply voltage. The fault is set when supply drops below a threshold for short periods, often during cranking or due to a poor connection.

SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number5 / 09

Possible causes

  • Poor battery cable connection high
  • Intermittent main relay medium
  • Connector with intermittent contact under vibration low

Inspection / repair

  • Difficulty: medium
  • DIY: possible
  • Estimated cost: 50–400 €
  • Estimated time: 0.3–2 h
  • Component: ecu power supply
  • Component: main relay
  • Component: battery terminals
  • 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