P0128
Coolant Thermostat Malfunction
Generic code
Fuel and Air Metering
High severity
Moderate repair
Free on OBD DashX
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What P0128 means
- The fault code P0128 indicates that the temperature of the engine coolant is below the thermostat regulating temperature, which is usually around 195 degrees Fahrenheit. This may cause the engine to run poorly and may even prevent it from starting.
Possible symptoms
- Illuminated check engine light
- Slow engine warm
- up
- Poor fuel economy
- Reduced heater output
- Poor engine performance
Possible causes
- Faulty thermostat
- Low coolant level
- Failed engine coolant temperature sensor
- Stuck open engine coolant bypass valve
- Malfunctioning engine control module (ECM)
Related parts
- Engine Coolant Temperature Sensor: The coolant temperature sensor measures the temperature of the engine coolant. Problems lead to engine overheating
Possible solutions
- Replace the faulty thermostat
- Top up the coolant level
- Replace the failed engine coolant temperature sensor
- Repair or replace the stuck open engine coolant bypass valve
- Replace the malfunctioning engine control module (ECM)
Free on OBD DashX
P0128 on OBD DashX
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