Powertrain, generic (extended)

P2556 Engine Coolant Level Sensor/Switch Circuit

Check engine lightUsually off
EmissionsNot relevant
Drive cycleNot required
Limp modeNo

P2556 is the general circuit code for the coolant level sensor or switch, normally fitted in the expansion tank. Deutz uses it on its EMR L1 engine control for industrial engines with the sub-code P2556-F0, a ground error, under SPN 111. Mercedes-Benz goes its own way and stores P2556-7B, meaning the sensor reports a fluid level that is too low. Bulletin LI20.30-P-078333 (August 2024) covers the EQB, where this code lands in the signal acquisition module SAM N10: air pushed into the circuit by the electric drive forms a cushion in the tank, so the level drops below the warning mark while driving; a red cap, filling 20 mm over max and if needed a revised tank fix it. LI09.41-N-079165 for OM654 Sprinter vans links the same code to coolant lost through an intercooler that leaks internally. P2560 is the plain low-level code.

Likely causes

Damaged wiring or ground at the level sensor
Air cushion in the expansion tank (Mercedes EQB)
Real coolant loss, e.g. internal charge air cooler leak

Symptoms

  • Low coolant warning in the cluster
  • Coolant level appears correct after opening the cap

Repair estimate

DifficultyMediumDIY possible
Parts and labour€20–400
Time0.3–2 h

Typical range across vehicles; the real cost depends on what the testing finds.

Parts involved

coolant level sensorsensor wiring

Related codes

P2557P2558P2559P2560

References: serdia.deutz.com, static.nhtsa.gov, static.nhtsa.gov.