GM Service Manual Online
For 1990-2009 cars only
AC Compressor Feedback: The scan tool displays On/Off. The state of the HVAC control module input for the A/C compressor status. When supply voltage is applied to the A/C compressor clutch coil, the voltage is also applied to the input terminal of the HVAC control module and the scan tool displays On. The scan tool displays Off when supply voltage is not applied to the A/C compressor clutch coil.

A/C Head Pressure: The scan tool displays Yes/No. The scan tool displays Yes when the HVAC control module receives a class 2 message from the PCM that the A/C high side pressure is at or above 2413 kPa (350 psi). This action disables an A/C request. The scan tool displays No when the HVAC control module receives a class 2 message from the PCM that the A/C high side pressure is below 2413 kPa (350 psi).

A/C High Side Pressure : The scan tool displays 0-3450 kPa (0-500 psi). The voltage applied to the PCM input from the A/C refrigerant pressure sensor is converted to a pressure value.

A/C High Side Pressure : The scan tool displays 0-5 volts. The voltage applied to the PCM input for the A/C refrigerant pressure sensor.

A/C Switch: The scan tool displays On/Off. The scan tool displays On when the A/C request switch is active. The scan tool displays Off when the A/C request switch is inactive.

AC Permission: The scan tool displays Withheld/Granted. The scan tool displays Granted when the HVAC control module determines that conditions for compressor clutch engagement are present. The scan tool displays Withheld when the HVAC control module determines that conditions for compressor clutch engagement are not present.

AC/Heater Door Actual: The scan tool displays 0-255 Counts. The voltage applied to the HVAC control module input for the mode door position is converted to a number between 0 and 255 where 51 Counts is approximately equal to 1 V.

AC/Heater Door Commanded: The scan tool displays 0-255 counts. The scan tool displays the desired mode door position as determined by the HVAC control module.

AC/Heater Motor Drive: The scan tool displays Stop, Increase, or Decrease. The scan tool displays the control decision for the actuator output as determined by the HVAC control module.

A/C Relay Command: The scan tool displays On/Off. The scan tool displays the control decision for the compressor clutch relay output as determined by the PCM.

A/C Request Signal: The scan tool displays Yes/No. The scan tool displays Yes when the PCM receives a class 2 message from the HVAC control module to engage the A/C compressor clutch. The scan tool displays No when the PCM receives a class 2 message from the HVAC control module to disengage the A/C compressor clutch.

Air Mix Door Actual: The scan tool displays 0-255 counts. The voltage applied to the auxiliary air temperature door position input of the auxiliary HVAC control module is converted to a number between 0 and 255 where 51 Counts is approximately equal to 1 V.

Air Mix Door Commanded: The scan tool displays 0-255 counts. The scan tool displays the desired auxiliary air temperature door position as determined by the auxiliary HVAC control module.

Air Mix Door Left Commanded: The scan tool displays 0-255 counts. The scan tool displays the desired left air temperature door position as determined by the HVAC control module.

Air Mix Door Right Commanded: The scan tool displays 0-255 counts. The scan tool displays the desired right air temperature door position as determined by the HVAC control module.

Battery Voltage: The scan tool displays 0-25 volts. The voltage measured from the battery positive voltage circuit and the ground circuit of the HVAC control module.

Battery Voltage: The scan tool displays 0-25 volts. The voltage measured from the battery positive voltage circuit and the ground circuit of the auxiliary HVAC control module.

Blower Speed: The scan tool displays Yes/No. The scan tool displays Yes when the HVAC control module interprets the input of the Off blower motor control circuit has battery positive voltage. This action disables an A/C request. The scan tool displays No when the HVAC control module interprets the input of the Off blower motor control circuit has no voltage.

Console Mode Door Actual: The scan tool displays 0-255 counts. The scan tool displays the desired console mode door position as determined by the auxiliary HVAC control module.

Console Mode Door Commanded: The scan tool displays 0-255 counts. The scan tool displays the desired console mode door position as determined by the auxiliary HVAC control module.

Defrost Door Actual: The scan tool displays 0-255 counts. The voltage applied to the defrost door position input of the HVAC control module is converted to a number between 0 and 255 where 51 Counts is approximately equal to 1 V.

Defrost Door Commanded: The scan tool displays 0-255 counts. The scan tool displays the desired defrost door position as determined by the HVAC control module.

Defrost Motor Drive: The scan tool displays Stop, Increase, or Decrease. The scan tool displays the control decision for the actuator output as determined by the HVAC control module.

Driver Override Switch: The scan tool displays Rear, Off, Low, Med, or High. The scan tool displays the position of the front auxiliary blower motor switch as determined by the auxiliary HVAC control module.

ECT Sensor: The scan tool displays -39 to 140°C (-38 to 284°F) . The voltage applied to the PCM input from the engine coolant temperature sensor is converted to a temperature value.

Engine Coolant Temp: The scan tool displays Yes/No. The scan tool displays Yes when the HVAC control module receives a class 2 message from the PCM that the engine coolant temperature is at or above 123°C (253°F). This action disables an A/C request. The scan tool displays No when the engine coolant temperature is below 123°C (253°F).

Engine Running: The scan tool displays Yes/No. The scan tool displays Yes when the HVAC control module receives a class 2 message from the PCM that the engine is not running. This action disables an A/C request. The scan tool displays No when the HVAC control module receives a class 2 message from the PCM that the engine is running.

Heater Water Valve: The scan tool displays Open or Closed. The scan tool displays the commanded state of the coolant bypass valve.

Ign. Since Current DTC: The scan tool displays 0-100. The number of the ignition cycles since the setting of the most recent current diagnostic trouble code (DTC).

Left Mix Door Actual: The scan tool displays 0-255 counts. The voltage applied to the left air temperature door position input of the HVAC control module is converted to a number between 0 and 255 where 51 Counts is approximately equal to 1 V.

Left Motor Drive: The scan tool displays Stop, Increase, or Decrease. The scan tool displays the control decision for the actuator output as determined by the HVAC control module.

Left Solar Sensor: The scan tool displays 0-255 counts. The voltage applied to the left sunload input of the BCM is converted to a number between 0 and 255 where 51 Counts is approximately equal to 1 V.

Left Temp. Detent Pos.: The scan tool displays a value from 0 to 18. The scan tool displays the position of the left air temperature switch. 0 is displayed for a full cold position. 18 is displayed for a full hot position.

Mode Door Actual: The scan tool displays 0-255 counts. The voltage applied to the auxiliary mode door position input of the auxiliary HVAC control module is converted to a number between 0 and 255 where 51 Counts is approximately equal to 1 V.

Mode Door Commanded: The scan tool displays 0-255 counts. The scan tool displays the desired auxiliary mode door position as determined by the auxiliary HVAC control module.

Mode Select Position: The scan tool displays Off, Auto, Defrost, Heater, Htr/Def, Bi-Level, Panel. The scan tool displays the state of mode operation.

Outside Air Temp: The scan tool displays Yes/No. The scan tool displays Yes when the HVAC control module interprets the input of the ambient air temperature sensor is at or below 1°C (35°F). This action disables an A/C request. The scan tool displays No when the HVAC control module interprets the input of the ambient air temperature sensor is above 1°C (35°F).

Pressure Cycle Switch: The scan tool displays Yes/No. The scan tool displays Yes when the HVAC control module interprets the input of the A/C low pressure switch is not grounded. This action disables an A/C request. The scan tool displays No when the HVAC control module interprets the input of the A/C low pressure switch is grounded.

Pressure Cycle Switch: The scan tool displays Low Pressure/Normal. The current state of the input from the A/C low pressure switch. The scan tool displays Low Pressure when the switch is open and displays Normal when the switch is closed. The low pressure switch opens when low side pressure decreases to approximately 151 kPa (22 psi) and closes when the low side pressure increases to approximately 275 kPa (40 psi).

Rear Blower Speed: The scan tool displays Off, Low, Med or High. The commanded state of the auxiliary blower motor as determined by the auxiliary HVAC control module.

Rear HVAC Fan Speed: The scan tool displays Off, Low, Med or High. The commanded state of the auxiliary blower motor as determined by the auxiliary HVAC control module.

Rear HVAC Motor Pos.: The scan tool displays Lower, Bi-level or Upper. The actual auxiliary mode door position as determined auxiliary HVAC control module.

Rear Temp. Select Sw.: The scan tool displays a value from 1 to 13 Counts. The scan tool displays the position of the auxiliary air temperature switch. 1 Counts is displayed for a full cold position. 13 Counts is displayed for a full hot position.

Recirculate Switch: The scan tool displays On/Off. The scan tool displays On when the recirculation switch is active. The scan tool displays Off when the recirculation switch is inactive.

Rec. Mode from Front Control: The scan tool displays Heater, Panel, Defrost, Bi-level or Htr./Def. The state of the primary HVAC system, received by class 2 message, as determined by the auxiliary HVAC control module.

Right Mix Door Actual: The scan tool displays 0-255 counts. The voltage applied to the right air temperature door position input of the HVAC control module is converted to a number between 0 and 255 where 51 Counts is approximately equal to 1 V.

Right Motor Drive: The scan tool displays Stop, Increase, or Decrease. The scan tool displays the control decision for the actuator output as determined by the HVAC control module.

Right Temp. Detent Pos.: The scan tool displays a value from 0 to 18. The scan tool displays the position of the right air temperature switch. 0 is displayed for a full cold position. 18 is displayed for a full hot position.

SWC Power: The scan tool displays On/Off. The scan tool displays the control decision for the supply voltage output to the steering wheel controls as determined by the BCM.

SWC Switch Voltage: The scan tool display 0-5 volts. The scan tool displays the voltage applied to the BCM input from the steering wheel controls.