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

P2181

Cooling System Performance

The engine cooling system does not reach or maintain the expected temperature within the diagnostic window — usually a stuck-open thermostat, but also a low coolant level or a stuck cooling fan that overcools the engine.

SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number1 / 81

Possible causes

  • Thermostat stuck open high
  • Coolant level low medium
  • Cooling fan stuck on low

Inspection / repair

  • Difficulty: medium
  • DIY: possible
  • Estimated cost: 80–400 €
  • Estimated time: 0.5–2.5 h
  • Component: thermostat
  • Component: coolant temperature sensor
  • Component: cooling fan
  • MIL / check engine light
  • emissions-relevant
  • drive cycle required

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