For 1990-2009 cars only
Cooling Fan After Run: The scan tool displays Not Requested/Requested.
If the engine coolant temperature is greater than 101°C (214°F) when the
engine is turned Off, the engine control module (ECM) will request low speed cooling
fan operation, in conjunction with the after-boil coolant pump operation. If the
engine coolant temperature is less than 101°C (214°F) after 60 seconds,
the ECM will turn the cooling fans Off. Otherwise, the ECM will turn off the cooling
fans and the after-boil coolant pump after 180 seconds on domestic vehicles,
and 300 seconds on export vehicles.
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 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 and internal resistance decreases, the voltage signal decreases and the ECM interprets the lower voltage as a warm engine.
Engine Coolant Fan: The scan tool displays OFF, Level 1, Level 2, or Level 3. When the scan tool displays Level 1, the ECM is commanding the low speed fan control relay On. When the ECM commands the low speed fan relay On, the left and right cooling fans are enabled in low speed. When the scan tool displays Level 2, the ECM is commanding the low speed, high speed, and S/P fan relays On. When the low speed, high speed, and S/P fan relays are On, the left and right cooling fans are enabled in high speed. When the scan tool displays Level 3, the ECM is commanding all fan relays On. When all fan relays are activated, the left and right cooling fans are enabled in high speed, and the auxiliary cooling fan, if equipped, is enabled.
Low Coolant Status: The scan tool displays OK/Low. When the scan tool displays Low, a low voltage level has been detected on the coolant level switch signal circuit, indicating a low coolant level condition.
Low Coolant Switch: The scan tool displays Open/Closed. When the scan tool displays Open, the coolant level has fallen below a certain level, causing the low coolant level switch to open, and the check coolant level display should be activated.
Water Pump Relay: The scan tool displays On/Off. The scan tool displays On when the HVAC control module has grounded the after-boil relay control circuit. Grounding the after-boil relay control circuit will turn on the after-boil relay, causing the after-boil coolant pump to turn on.
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 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 and internal resistance decreases, the voltage signal decreases and the ECM interprets the lower voltage as a warm engine.
Engine Coolant Fan: The scan tool displays OFF, Level 1, Level 2, or Level 3. When the scan tool displays Level 1, the ECM is commanding the low speed fan control relay On. When the ECM commands the low speed fan relay On, the left and right cooling fans are enabled in low speed. When the scan tool displays Level 2, the ECM is commanding the low speed, high speed, and S/P fan relays On. When the low speed, high speed, and S/P fan relays are On, the left and right cooling fans are enabled in high speed. When the scan tool displays Level 3, the ECM is commanding all fan relays On. When all fan relays are activated, the left and right cooling fans are enabled in high speed, and the auxiliary cooling fan, if equipped, is enabled.
Low Coolant Status: The scan tool displays OK/Low. When the scan tool displays Low, a low voltage level has been detected on the coolant level switch signal circuit, indicating a low coolant level condition.
Low Coolant Switch: The scan tool displays Open/Closed. When the scan tool displays Open, the coolant level has fallen below a certain level, causing the low coolant level switch to open, and the check coolant level display should be activated.
Water Pump Relay: The scan tool displays On/Off. The scan tool displays On when the HVAC control module has grounded the after-boil relay control circuit. Grounding the after-boil relay control circuit will turn on the after-boil relay, causing the after-boil coolant pump to turn on.
