GMC Sierra 2007-2020 Engine Coolant Temperature Sensor: A Complete Guide
Learn the symptoms of a failing coolant temp sensor and how to choose the right replacement for your truck.
- A bad ECT sensor often causes a Check Engine Light with codes like P0117, P0118, or P0128.
- For a P0128 code, consider replacing the thermostat at the same time as the sensor, as a stuck thermostat is a very common cause.
- Replacement is a simple, DIY-friendly job that most owners can complete in under an hour with basic tools.
- Quality aftermarket brands provide a reliable and cost-effective alternative to more expensive OEM parts for this specific component.
Understanding ECT Sensor Failures in Your Sierra
When the engine coolant temperature sensor starts to fail, it sends incorrect data to your truck's computer. This can make the computer think the engine is hot when it's cold, or cold when it's hot. This confusion leads to a variety of performance problems. It's a common wear item, but catching it early can prevent further issues.
Symptoms of a Bad Engine Coolant Temperature Sensor
A failing ECT sensor can cause several noticeable problems. Here are the most common signs you'll see in a 2007-2020 Sierra:
- Check Engine Light: This is often the first and most obvious sign. A faulty sensor will trigger diagnostic trouble codes (DTCs), most commonly P0117 (low input), P0118 (high input), or P0128 (coolant temperature below thermostat regulating temperature).
- Cooling Fans Running Constantly: The truck's computer may default to running the cooling fans at full speed as a precaution, even when the engine is cold. This can drain the battery if the fans continue to run after the truck is shut off. 🎬 Watch how to fix cooling fans that won't turn off.
- Inaccurate Temperature Gauge: The temperature gauge on your dashboard may not move from the cold reading, or it might show erratic behavior.
- Poor Fuel Economy: If the sensor tells the computer the engine is always cold, the computer will enrich the fuel mixture, causing the truck to use more gas than necessary.
- Black Smoke from Exhaust: A rich fuel mixture can result in unburned fuel leaving the engine, which appears as black smoke from the tailpipe.
P0128 Code: Sensor or Thermostat?
The P0128 code is very common on these trucks. While it can be caused by a bad ECT sensor, it is frequently caused by a thermostat that is stuck open. Many mechanics recommend replacing both the thermostat and the ECT sensor at the same time to fully resolve the issue and prevent a comeback.
🎬 Learn more about diagnosing and fixing the P0128 code.Choosing the Right Aftermarket ECT Sensor
For a simple electronic part like an ECT sensor, a quality aftermarket brand offers excellent value compared to the more expensive OEM part. The key is to choose a reputable brand to ensure reliability.
- Professional-Grade Aftermarket (Standard Ignition, Four Seasons): Brands like Standard and Four Seasons are well-known in the repair industry. They produce reliable sensors that meet or exceed OEM specifications and are a trusted choice for daily drivers and work trucks.
- Standard Aftermarket (Global Parts, True Tech): These brands provide a cost-effective solution for a repair. While they may not have the long-standing reputation of the professional-grade brands, they are a functional alternative for budget-conscious repairs.
Avoid the cheapest, no-name sensors from online marketplaces, as their quality can be inconsistent and lead to premature failure.
Check the Connector
Over the long 2007-2020 production run, GM sometimes used different electrical connectors. When ordering, it's wise to visually compare the connector on the new part to the one on your truck to ensure it's a perfect match. Some replacement sensors may require a new pigtail connector to be spliced in.
🎬 See how to replace a damaged coolant sensor electrical connector.GMC Sierra ECT Sensor Replacement Cost
The cost to replace the ECT sensor is very reasonable, especially if you do it yourself. The part itself is inexpensive, and the labor is straightforward.
| Item | Cost Range |
|---|---|
| New Aftermarket ECT Sensor | $19.11 - $31.90 |
| New OEM ECT Sensor | $35 - $60 |
| Estimated Shop Labor | $95 - $170 |
| Estimated Total (Shop Repair) | $116 - $230 |
Frequently Asked Questions (FAQ)
Where is the ECT sensor located on the GMC Sierra?
On most V8 engines (like the 5.3L and 6.2L) from 2007-2020, the ECT sensor is located on the driver's side cylinder head, toward the front of the engine, near the thermostat housing. You will likely need to remove the plastic engine cover and air intake tube to access it.
Can I replace the ECT sensor myself?
Yes, this is a great DIY job for beginners. It typically requires only basic hand tools like a socket set and pliers. The job can be done in under an hour. You will lose a small amount of coolant, so have a drain pan ready.
Do I need to drain all the coolant to replace the sensor?
No. You don't need to drain the entire system. Some coolant will spill out when you remove the old sensor. To minimize the mess, have the new sensor ready to screw in quickly. After installation, top off the coolant reservoir as needed.
Are there any recalls for the ECT sensor on the GMC Sierra?
As of early 2026, there are no specific recalls for the engine coolant temperature sensor itself. There was a Technical Service Bulletin (TSB 20-NA-167) for 2019-2020 models with the LV3 engine showing a P0128 code, which required a software update, not a part replacement. Always check for TSBs related to your specific year and engine before replacing parts.
Helpful Videos
Technical Specifications
OEM Part Numbers: 12608814 15326388 12191170 55490805
Typically a 2-pin, brass sensor that screws into the cylinder head or engine block. Uses a threaded fitting with pre-applied sealant.
We Have This Part in Stock
The information in this article is provided for general reference and educational purposes only. Vehicle specifications, procedures, and part compatibility can vary by production date, trim level, and region. Always consult your vehicle's factory service manual and verify part numbers before purchasing or performing repairs. Safety-critical components such as airbags, seat belts, and braking systems should be installed by a qualified professional.
- GMC Sierra:
- 🎬 Helpful Videos
- 🛍️ Shop This Part
- Understanding ECT Sensor Failures in Your Sierra
- Symptoms of a Bad Engine Coolant Temperature Sensor
- P0128 Code: Sensor or Thermostat?
- Choosing the Right Aftermarket ECT Sensor
- Check the Connector
- GMC Sierra ECT Sensor Replacement Cost
- Frequently Asked Questions (FAQ)
- 🎟️ Get 5% Off