What does code P0118 mean on a Mercedes-Benz and is it safe to drive?
P0118: Engine Coolant Temperature Circuit High Input. Here's what it means on your Mercedes-Benz, what usually causes it, what repairs typically cost, and how safe it is to keep driving.
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What this code means
The engine coolant temperature (ECT) sensor is reporting a voltage signal that is too high, which the PCM interprets as an extremely cold or open-circuit condition. This is opposite to P0117 (low input) and often means the sensor or its wiring has failed open.
Common causes for your Mercedes-Benz
- Failed engine coolant temperature sensor
- Open circuit in ECT sensor wiring
- Corroded or damaged sensor connector
- Low coolant level exposing the sensor
Symptoms
- Check Engine Light
- Engine runs rich (PCM thinks it is always cold)
- Poor fuel economy
- Hard starting when warm
Typical fixes
- Replace engine coolant temperature sensor
- Inspect and repair wiring and connector
- Check coolant level
Repair cost range
For a Mercedes-Benz, repairs for P0118 often fall between $50 and $200, depending on the cause and whether you use OEM or aftermarket parts. Labor rates vary by location.