P0128: Coolant Thermostat (Coolant Temp Below Thermostat Regulating Temperature)

What does P0128 mean?

P0128 is a diagnostic trouble code indicating "Coolant Thermostat (Coolant Temp Below Thermostat Regulating Temperature)". This code relates to your vehicle's cooling system and should be diagnosed to determine the root cause. The severity level helps indicate how urgently this should be addressed.

Symptoms you may notice

• Check engine light (MIL) illuminated on dashboard
• Engine overheating
• Temperature gauge reading high
• Heater not working properly

Common causes

• Stuck thermostat (open or closed)
• Low coolant level or coolant leak
• Failed coolant temperature sensor
• Faulty water pump
• Blocked radiator

What should you do?

Schedule a diagnostic appointment at your earliest convenience. The vehicle is generally safe to drive short distances, but the underlying issue should be addressed to prevent it from worsening.