P0128
Coolant Thermostat Below Regulating Temperature
2016-2021 Mazda CX-3 2.0L I4
Low SeverityPowertrainGeneric (SAE)
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
- P0001Fuel Volume Regulator Control Circuit/Open
- P0002Fuel Volume Regulator Control Circuit Range/Performance
- P0002Fuel Volume Regulator Control Circuit Range/Performance
- P0003Fuel Volume Regulator Control Circuit Low
- P0003Fuel Volume Regulator Control Circuit Low
- P0004Fuel Volume Regulator Control Circuit High
- P0004Fuel Volume Regulator Control Circuit High
- P0010Intake Camshaft Position Actuator Circuit/Open Bank 1
- P0010Intake Camshaft Position Actuator Circuit/Open Bank 1
P0128 on Other Vehicles
Common Questions
What does code P0128 mean on a 2016-2021 Mazda CX-3?
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 CX-3?
Common symptoms of P0128 include: Check Engine Light, Poor fuel economy, Heater not getting hot, Engine running cool.
What causes P0128 on a 2016-2021 Mazda CX-3?
Common causes of P0128 include: Stuck-open thermostat, Missing thermostat, Faulty ECT sensor, Cooling fan stuck on.