P0117 on a Subaru: 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 Subaru

On a Subaru, P0117 means the engine coolant temperature sensor is reading full hot because the signal voltage is too low. The usual causes are a failed sensor or a shorted wire. The computer may run the engine rich and turn the cooling fan on early.

Is P0117 common on Subarus?

Outbacks, Foresters, Imprezas, and Legacys commonly see P0117 when the ECT sensor fails or its connector corrodes. The sensor sits on the engine and is inexpensive and easy to replace, so this is usually a quick fix.

Commonly reported on: Outback, Forester, Impreza, Legacy.

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	$15–50
Repair the wiring or connector	Mechanic	$50–150
Have a shop replace the sensor and verify the circuit	Mechanic	$100–220