P0117 on a GMC: Causes, Fixes & Repair Cost

🟠 Moderate severity · drivable

Safe to drive, but the engine may run rich and the cooling fans may run at full speed until the sensor circuit is fixed.

What P0117 means on a GMC

On a GMC, P0117 means the engine coolant temperature (ECT) sensor is sending a low-voltage signal that the computer reads as the engine being very hot. GM engines use a two-wire ECT sensor near the thermostat housing, and a shorted sensor or signal wire is the usual cause. While the code is active the computer may command the fans to run full speed and add fuel.

Is P0117 common on GMCs?

P0117 shows up on Sierra and Yukon trucks and SUVs with higher mileage. Corroded connectors and chafed wiring are well-known trouble spots on GM engines, so the sensor circuit itself is usually where the fault lives.

Commonly reported on: Sierra, Yukon, Terrain, Acadia.

Symptoms

Check engine light on
Cooling fans running at full speed
Poor fuel economy
Temperature gauge reading high while the engine is cool

Common causes

most common: Faulty coolant temperature sensor
common: Sensor signal wire shorted to ground
common: Corroded or loose connector
less common: Wiring chafed near the engine

How to fix it

Fix	DIY?	Typical cost
Replace the coolant temperature sensor	Yes	$20–50
Repair the sensor wiring or connector	Mechanic	$50–150
Have a shop diagnose the circuit	Mechanic	$80–120