The Engine Scan Tool Data Definitions contains a brief description of all engine related parameters available on the scan tool. The list is in alphabetical order. A given parameter may appear in any one of the data lists. In some cases, the parameter may appear more than once or in more than one data list in order to group certain related parameters together.

A/C Clutch Feedback Signal: The scan tool displays ON or OFF. This parameter indicates the actual state of the A/C compressor clutch. When the scan tool displays ON, the A/C clutch should be engaged.

A/C Fan Request: The scan tool displays YES or NO. This parameter indicates the commanded state of the engine cooling fan low speed relay.

A/C High Side Pressure: The scan tool displays 15-452 psi/103-3116 kPa/0-5 volts. This parameter represents the A/C refrigerant pressure sensor signal. The amount of pressure indicates the amount of load that the A/C compressor places on the engine. The powertrain control module (PCM) uses this information in order to adjust idle and in order to control the cooling fans.

A/C LED: The scan tool displays ON or OFF. This parameter indicates the commanded state of the A/C LED indicator. When the scan tool displays ON, the A/C clutch should be engaged.

A/C Relay Command: The scan tool displays ON or OFF. The A/C Relay Command parameter represents the PCM commanded state of the A/C clutch relay control circuit. When the scan tool displays ON, the A/C clutch control relay should be energized.

A/C Request Signal: The scan tool displays Yes or No. The A/C Request displays the state of the A/C request input circuit from the HVAC controls. The PCM uses the A/C request signal in order to determine whether the A/C compressor operation is being requested.

A/C Request Switch: The scan tool displays ON or OFF. This parameter indicates the commanded state of the A/C request switch. When the scan tool displays ON, the A/C clutch should be engaged.

ECT Sensor:  The scan tool displays a range of -39 to +140°C (-38 to +284°F). The engine coolant temperature (ECT) sensor is mounted in the cylinder head of the left bank. 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 the voltage 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.

Fan Control: The scan tool displays ON or OFF. This parameter indicates if the engine cooling fan low speed relay has been commanded ON or OFF.

Fan Requested: The scan tool displays YES or NO. This parameter indicates if the engine cooling fan low speed relay has been requested ON or OFF.

Fan Run On: The scan tool displays ACTIVE or INACTIVE. This parameter indicates if the engine cooling fan low speed relay has been commanded ON or OFF.

Fan Run On: The scan tool displays 0. This parameter indicates the number of seconds that the engine cooling fan low speed relay has been commanded ON.

FC Relay 1 Command: The scan tool displays ON or OFF. The scan tool displays ON when the PCM commands a coolant fan relay ON. Both fans are enabled on low speed when the PCM commands the fan one relay control ON.

FC Relay 2 Command: The scan tool displays ON or OFF. The scan tool displays ON when the PCM commands a coolant fan relay ON. Both cooling fans are enabled on high speed when the PCM commands both fan control circuits ON.

Low Speed Fan Relay: The scan tool displays ON or OFF. This parameter indicates if the engine cooling fan low speed relay has been commanded ON or OFF.