Coolant Thermostat Below Regulating Temperature
2008-2008 Mazda Tribute 2.5L I4
The 2008 Mazda Tribute is equipped with a 2.5L inline-4 engine. Below you'll find detailed p0128 diagnostic code information including labor time estimates, cost ranges, and technician notes specific to this engine configuration.
Description
The engine coolant has not reached the expected temperature within a specified time after startup.
Symptoms
- Check Engine Light
- Poor fuel economy
- Heater not getting hot
- Engine running cool
Common Causes
- Stuck-open thermostat
- Missing thermostat
- Faulty ECT sensor
- Cooling fan stuck on
Diagnostic Steps
- Monitor ECT warmup curve
- Check thermostat
- Verify fan operation
- Test ECT sensor
Repair Notes
Replace thermostat.
Related Codes
Other Powertrain Codes
- P0001Fuel Volume Regulator Control Circuit/Open
- P0002Fuel Volume Regulator Control Circuit Range/Performance
- P0003Fuel Volume Regulator Control Circuit Low
- P0004Fuel Volume Regulator Control Circuit High
- P0010Intake Camshaft Position Actuator Circuit/Open Bank 1
- P0011Intake Camshaft Position Timing Over-Advanced Bank 1
- P0012Intake Camshaft Position Timing Over-Retarded Bank 1
- P0013Exhaust Camshaft Position Actuator Circuit/Open Bank 1
- P0014Exhaust Camshaft Position Timing Over-Advanced Bank 1
- P0015Exhaust Camshaft Position Timing Over-Retarded Bank 1
P0128 on Other Vehicles
Common Questions
What does code P0128 mean on a 2008-2008 Mazda Tribute?
P0128 stands for "Coolant Thermostat Below Regulating Temperature". The engine coolant has not reached the expected temperature within a specified time after startup.
What are the symptoms of P0128 on a Mazda Tribute?
Common symptoms of P0128 include: Check Engine Light, Poor fuel economy, Heater not getting hot, Engine running cool.
What causes P0128 on a 2008-2008 Mazda Tribute?
Common causes of P0128 include: Stuck-open thermostat, Missing thermostat, Faulty ECT sensor, Cooling fan stuck on.
Last updated: March 2026