Cooling System Performance
The engine control module has detected that the cooling system is not maintaining proper operating temperature. This code indicates the coolant temperature is either running significantly hotter or colder than the target range, which can damage the engine and affect fuel economy and emissions.
What You Might Notice
- Engine temperature gauge reading high or low
- Red temperature warning light illuminated
- Engine overheating or running cold
- Reduced fuel economy
- Engine running rough or hesitating
Most Common Causes
- 1
Faulty Thermostat
A stuck-open or stuck-closed thermostat prevents proper coolant flow regulation, causing the engine to run too hot or too cold.
- 2
Malfunctioning Coolant Temperature Sensor
A defective engine coolant temperature (ECT) sensor sends incorrect temperature readings to the PCM, triggering the code even if the cooling system is functioning normally.
- 3
Low Coolant Level
Insufficient coolant due to leaks or evaporation reduces the system's ability to regulate engine temperature effectively.
- 4
Faulty Water Pump or Cooling Fan
A failing water pump or electric cooling fan that doesn't engage properly restricts coolant circulation or heat dissipation.
How to Diagnose It
- 1
Check Faulty Thermostat — A stuck-open or stuck-closed thermostat prevents proper coolant flow regulation, causing the engine to run too hot or too cold.
- 2
Check Malfunctioning Coolant Temperature Sensor — A defective engine coolant temperature (ECT) sensor sends incorrect temperature readings to the PCM, triggering the code even if the cooling system is functioning normally.
- 3
Check Low Coolant Level — Insufficient coolant due to leaks or evaporation reduces the system's ability to regulate engine temperature effectively.
- 4
Check Faulty Water Pump or Cooling Fan — A failing water pump or electric cooling fan that doesn't engage properly restricts coolant circulation or heat dissipation.
How to Fix It
- 1
Test and Replace Thermostat
Perform a coolant temperature test to determine if the thermostat is stuck. If faulty, drain the cooling system and replace the thermostat with an OEM-equivalent unit.
- 2
Test and Replace Coolant Temperature Sensor
Use a multimeter to test the ECT sensor resistance across the operating temperature range. If readings are out of specification, replace the sensor.
- 3
Check and Top Off Coolant
Inspect the cooling system for visible leaks. Top off the coolant reservoir with the correct type for your vehicle. If the level drops again, locate and repair the source of the leak.
- 4
Inspect and Replace Water Pump or Cooling Fan
Test the electric cooling fan for operation when the engine reaches operating temperature. Inspect the water pump for leaks or noise. Replace components as needed.
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