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.
Scan Tool Data Definitions
- Displayed Coolant Temp
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The scan tool displays -39°C to +140°C (-38°F to +284°F). This is the actual indication of the displayed coolant temperature.
- ECT
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The scan tool displays -39°C to +140°C (-38°F to +284°F). The engine coolant temperature (ECT) sensor is mounted in the coolant stream. The powertrain control module (PCM) applies 5 volts to the ECT sensor circuit. The sensor is a thermistor which changes internal resistance as temperature changes. When the sensor is cold (internal resistance high), the PCM monitors a high signal voltage and interprets it as a cold engine. As the sensor warms (internal resistance decreases), the voltage signal decreases and the PCM interprets the lower voltage as a warm engine.
- High Speed Fan Relay
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The scan tool displays On and Off. It represents the commanded state of the high speed cooling fan relay as commanded by the PCM.
- Low Speed Fan Relay
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The scan tool displays On and Off. It represents the commanded state of the low speed cooling fan relay as commanded by the PCM.
- Monitored Coolant Temp
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The scan tool displays -39°C to +140°C (-38°F to +284°F). This is the actual coolant temperature as received from the powertrain control module (PCM).
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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.