P0128 Chevrolet Traverse
Coolant Thermostat Below Regulating Temperature · Powertrain Code · Medium · Repair: Easy
What is P0128?
The engine coolant is not reaching the expected temperature. Most commonly caused by a stuck-open thermostat, low coolant level, or a faulty coolant temperature sensor.
When the Chevrolet Traverse triggers code P0128 (coolant thermostat below regulating temperature), it typically points to an issue in the powertrain system. Below you'll find the most common causes, symptoms, and repair options specific to the Chevrolet Traverse.
This repair is rated easy, meaning basic tools, no lift needed.
Diagnostic data on this page is compiled from publicly available repair resources and technical service bulletins. Always have a qualified mechanic confirm the diagnosis before authorizing repairs on your Chevrolet Traverse.
Common Causes on Chevrolet Traverse
- Thermostat stuck open on 3.6L V6 LFY/LGX engine
- Thermostat housing gasket deterioration from Dex-Cool degradation
- Coolant temperature sensor wiring corroded at connector
- Water pump internal bypass allowing coolant flow past thermostat
Symptoms
- Engine takes abnormally long to reach operating temperature
- Heater blows lukewarm or cold air
- Temperature gauge stays below normal or never reaches middle
- Slightly reduced fuel economy from extended open-loop operation
- Check engine light illuminated
Notes for Chevrolet Traverse
Thermostat on the 3.6L V6 is on the driver side of the engine; straightforward access.