P0117 on a BMW: Causes, Fixes & Repair Cost

🟠 Moderate severity · drivable

Safe to drive for a short time, but the engine may run rich and burn extra fuel, and the cooling fan may run constantly.

What P0117 means on a BMW

On a BMW, P0117 means the engine coolant temperature sensor is reading very hot because the signal voltage is too low. The usual cause is a failed sensor or shorted wiring. The computer may run the engine rich and keep the electric cooling fan running.

Is P0117 common on BMWs?

3 Series, 5 Series, and X3 models can see P0117 as the coolant temperature sensor ages or its connector corrodes. BMW coolant sensors are inexpensive, though some engines mount them in tighter spots that take more labor to reach.

Commonly reported on: 3 Series, 5 Series, X3, X5.

Symptoms

Check engine light on
Cooling fan runs constantly
Poor fuel economy from rich running
Hard starting when the engine is cold

Common causes

most common: Faulty coolant temperature sensor
common: Sensor wiring shorted to ground
common: Corroded or loose connector terminals
less common: Damaged wiring near the sensor

How to fix it

Fix	DIY?	Typical cost
Replace the coolant temperature sensor	Yes	$25–70
Repair the wiring or connector	Mechanic	$80–200
Have a shop replace the sensor and verify the circuit	Mechanic	$150–300