P0128 Nissan Pathfinder
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 Nissan Pathfinder 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 Nissan Pathfinder.
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 Nissan Pathfinder.
Common Causes on Nissan Pathfinder
- Thermostat stuck open on 2.5L QR25DE or 3.5L VQ35DE V6 engine
- Coolant temperature sensor failure common on Rogue 2.5L
- Thermostat housing gasket deteriorated from age
- Low coolant from CVT cooler line seepage
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 Nissan Pathfinder
Rogue is the most common Nissan to throw P0128; thermostat is accessible from above.