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

P2561

A/C Control Module Requested MIL Illumination

The A/C / HVAC control module has requested the ECM to illuminate the malfunction indicator (MIL) because of an emissions-relevant fault on its side. The original fault is stored in the HVAC module — this code only signals that the ECM has honoured the request.

SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number5 / 61

Possible causes

  • Internal fault in the HVAC module — read its DTCs high

Inspection / repair

  • Difficulty: medium
  • DIY: shop recommended
  • Estimated cost: 50–800 €
  • Estimated time: 0.3–3 h
  • Component: hvac module
  • MIL / check engine light
  • emissions-relevant

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