P0128
Coolant Thermostat Coolant Temperature Below Regulating Temperature
📖 What Does P0128 Mean?
The engine is not reaching proper operating temperature within the expected time frame, usually due to a thermostat stuck open.
Symptoms
Poor heater performance, increased fuel consumption, slow engine warm-up, temperature gauge reading low, check engine light.
Common Causes
Thermostat stuck open, faulty coolant temperature sensor, low coolant level, air in cooling system, faulty radiator fan relay.
Possible Solutions
Replace thermostat, check coolant temperature sensor, top off coolant and bleed air from system, test radiator fan operation.
Recommended Parts & Tools
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Frequently Asked Questions about P0128
How serious is P0128?
This code has a low severity level. While not immediately dangerous, this should be addressed during your next service.
Can I drive with P0128?
Generally safe to drive, but should be addressed during your next service.
How much does it cost to fix P0128?
Repair costs vary depending on the root cause, but typically range from $50-150 including parts and labor.
Related Diagnostic Codes
Other codes that may appear with P0128
Fuel and Air Metering Code P0100
Mass Air Flow Sensor Circuit Range/Performance Problem
Mass Air Flow Sensor Circuit Low Input
Mass Air Flow Sensor Circuit High Input
Fuel and Air Metering Code P0104
Fuel and Air Metering Code P0105
💡 Why These Codes Are Related:
- • Similar Issues: Same root cause or component failure
- • Related Problems: Often occur together due to system interactions
- • Sequential Codes: Progressive failure stages or multiple sensors
- • Same System: Components within the same automotive system