Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Theory Of Operation
This diagnostic is used to detect an Engine Coolant Temperature (ECT) Sensor that is in range but reading incorrectly. Unlike the temperature sensor performance diagnostic that runs only on cold starts and compares all of the temperature sensor values, this diagnostic runs continuously. The Powertrain Control Module (PCM) models a predicted ECT Sensor value and compares that model to the actual ECT Sensor. If the difference is too large, a counter starts to increment. When the counter reaches a calibrated threshold, a fault is set.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.