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
- ECT Sensor
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The scan tool displays -40 to +151°C (-40 to +304°F). The engine coolant temperature (ECT) sensor is mounted in the coolant stream. The engine control module (ECM) 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 ECM 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 ECM interprets the lower voltage as a warm engine.
- FC Relay 1 Command
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The scan tool displays ON or OFF. This parameter indicates the state of the driver circuit for this device.
- FC Relay 2 and 3 Command
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The scan tool displays ON or OFF. This parameter indicates the state of the driver circuit for this device.
- FC Relay 1 Circuit Status
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The scan tool displays OK or Fault. This parameter indicates the status for the state of the driver circuit for this device.
- FC Relay 2 and 3 Circuit Status
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The scan tool displays OK or Fault. This parameter indicates the status for the state of the driver circuit for these devices.
- Ignition 1 Signal
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The scan tool displays Voltage. This parameter indicates the status of voltage at the ECM.
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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.