P2557: Engine Coolant Level Sensor/Switch Circuit Range/Performance

P2557 means the coolant level signal is electrically present but not believable. The Deutz EMR L1 engine control is the one documented user and fills the code twice under SPN 111: P2557-00 for a sensor value outside the valid range, and P2557-1C when the supply voltage feeding the level sensor is itself out of range. The second case is worth checking first, because a weak or overloaded sensor supply skews the reading without any fault at the sensor. Mechanical effects can also confuse a level sensor; Mercedes describes for the EQB how an air cushion in the expansion tank pushed the measured level below the warning mark although enough coolant was present. Shorts to ground or open lines belong to P2558, a short to battery to P2559, and P2556 is the general circuit code. Expect a coolant warning that is unreliable.

Symptoms

• Coolant level warning appears and disappears
• Engine protection warning on industrial engines

Most likely causes

• Sensor supply voltage out of range (Deutz P2557-1C)
• Level sensor element contaminated or failing
• Air pocket or foam in the expansion tank distorting the reading

What to check, in order

Start with the simplest. You can tick off each step.

1. With the engine cold, check the coolant level; never do this when the system is hot
2. Compare the reading with other engine data while varying the engine speed.
3. Check the actual temperature in live data
4. Make sure the fan comes on when it should
5. Check the thermostat and connector
6. Measure the sensor and replace it if its readings do not make sense

Good to know

• Repair difficulty: medium

What each character of P2557 means

• P: Powertrain: engine and transmission
• 2: Generic code: same on every make
• 5: Speed and idle
• 57: Specific fault in that system

Frequently asked questions

Can I keep driving with code P2557?

Watch the temperature gauge. If it climbs or a warning appears, stop the car in a safe place and turn off the engine: overheating can cause serious damage.

What causes code P2557?

The most common causes are: sensor supply voltage out of range (Deutz P2557-1C); level sensor element contaminated or failing; air pocket or foam in the expansion tank distorting the reading.

Related codes

• P2556Engine Coolant Level Sensor/Switch Circuit
• P2558Engine Coolant Level Sensor/Switch Circuit Low
• P2559Engine Coolant Level Sensor/Switch Circuit High
• P2560Engine Coolant Level Low

Sources

• serdia.deutz.com: DTCList EMRL1 MainECU EN
• static.nhtsa.gov: MC 11006690 0001

Values and procedures vary by manufacturer. If it affects brakes, steering, fuel or high voltage, see a professional. Updated: 2026-11-04. How we build these pages.