GM Service Manual Online
For 1990-2009 cars only
Coolant Hot Lamp: The scan tool displays On/Off. This parameter indicates the state of the engine coolant temperature indicator as commanded by the instrument panel cluster (IPC).

ECT Sensor: The scan tool displays -40°C to +151°C (-40°F 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 (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.

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 On or Off. The PCM is commanding Fan Control relay 1 On when the scan tool indicates On. When the PCM commands the Fan Control relay 1 On, both fans are enabled on low speed.

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. The PCM is commanding all three fan control relays on when the scan tool indicates On. When all fan control relays are activated, both cooling fans are enabled on high speed.

Low Coolant Input: The scan tool displays Active/Inactive. This parameter indicates the state of the low coolant level indicator control circuit.

Low Coolant Lamp: The scan tool displays On/Off. This parameter indicates the state of the low engine coolant level indicator as commanded by the IPC.