Faulty Engine Cooling System

The computer monitors the engine temperature using a sensor. If that sensor sends incorrect temperature readings, it might think the engine is too hot or too cold, which can lead to poor performance or even damage.

The engine control module (ECM) expects the coolant temperature to be within a specific range (typically between 160°F and 240°F). If the sensor reading deviates significantly, for example, below 140°F or above 260°F, the ECM will trigger this code.

Don't just throw parts at it. Walk through these in order — each step tells you whether to keep going or stop and fix what you found.

1. 11. Check the coolant level in the reservoir. If low, fill to the proper level. Decision: If coolant level was low, top off and retest; if not low, move to step 2.
2. 22. Inspect the wiring and connector to the coolant temperature sensor for any signs of damage, corrosion, or looseness. Decision: If any issues found, repair the wiring/connector; if none found, move to step 3.
3. 33. Test the coolant temperature sensor with a multimeter to ensure it is providing accurate readings at different temperatures (should read approximately 2.5kΩ at 70°F). Decision: If readings are incorrect, replace the coolant temperature sensor; if readings are correct, move to step 4.
4. 44. Check for any coolant leaks around the engine and hoses. Decision: If leaks are found, repair them; if no leaks are present, investigate the thermostat condition.

• Faulty coolant temperature sensor
• Corroded or damaged wiring harness
• Coolant leaks causing low fluid level
• Incorrect coolant type
• Thermostat stuck open or closed

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