Engine Protection Active, Engine Coolant Temperature Fault

The computer thinks your engine is overheating or the temperature sensor is bad, which can cause engine damage if you keep running it.

The engine control module (ECM) sees coolant temperature values outside of the expected range, triggering a fault.

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 engine coolant level. If it's low, top it off and see if the code returns after some driving. Decision: If code clears, monitor for future issues. If not, go to step 2.
2. 22. Inspect the wiring and connector at the coolant temperature sensor for damage or corrosion. Repair if needed. Decision: If repaired, clear the code and retest. If code comes back, go to step 3.
3. 33. Test the coolant temperature sensor using a multimeter. Measure the resistance: At 70°F (21°C), it should be about 2,800 ohms. At 210°F (99°C), about 250 ohms. Decision: If readings are off, replace the sensor. If normal, go to step 4.
4. 44. Check the thermostat operation. When the engine is warm, the upper radiator hose should be hot. If not, the thermostat may be stuck closed, and you should replace it.

• Faulty coolant temperature sensor
• Wiring issues to the sensor (shorts, opens)
• Low coolant level
• Thermostat malfunction

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