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: 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 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, the internal resistance high. The powertrain control module (PCM) monitors a high signal voltage and interprets it as a cold engine. As the sensor warms, the internal resistance decreases. The voltage signal decreases and the PCM interprets the lower voltage as a warm engine.
FC Relay 1 Circuit Status: The scan tool displays OK or Fault. This parameter indicates the state of the driver circuit for this device.
FC Relay 1 Command: The scan tool displays OK or Fault. This parameter indicates the state of the driver circuit for this device.
FC Relay 2 and 3 Circuit Status: The scan tool displays OK or Fault. This parameter indicates the state of the driver circuit for this device.
FC Relay 2 and 3 Command: The scan tool displays On or Off. This parameter indicates the state of the high speed fan relay driver.
High Coolant Temp Lamp: The scan tool displays On/Off. The requested state of the engine coolant temperature indicator as commanded by the PCM. The body control module (BCM) receives a class 2 message from the PCM requesting illumination.
Low Coolant Lamp: The scan tool displays On/Off. The requested state of the low engine coolant indicator as commanded by the BCM.
Low Coolant Level: The scan tool displays OK/Low. This parameter indicates when the engine coolant level is low. The scan tool displays Low when the BCM detects the engine coolant level switch is closed.
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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.