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

P2556

Engine Coolant Level Sensor/Switch Circuit

General electrical fault on the engine coolant level sensor/switch circuit. Many vehicles use a simple float-switch in the expansion tank, others use a continuous-level analog sensor. With the input invalid the ECM cannot warn for low coolant before overheating starts.

SystemPowertrain
Typegeneric / SAE
GroupP2
Range / number5 / 56

Possible causes

  • Open or shorted wiring to the sensor high
  • Corroded connector at the expansion tank medium

Inspection / repair

  • Difficulty: easy
  • DIY: possible
  • Estimated cost: 40–250 €
  • Estimated time: 0.2–1 h
  • Component: coolant level sensor
  • Component: sensor wiring
  • 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