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7A-26 Heating, Ventilation and Air Conditioning:
Scan Tool Parameter
Operating Conditions: Engine idling, A/C ON, ambient air temperature between 22-27°C (70-80°F)
Rear Defrost State
Recirculation Switch
Right Sunload Sensor
Scan Tool Data Definitions - HVAC -
Automatic
Use the Scan Tool Data Display Values and Definitions
Information in order to assist in diagnosing control
module problems. Compare the vehicles actual scan tool
data with the typical data display value table information.
Use the data information in order to aid in understanding
the nature of the problem when the vehicle does not
match with the typical data display values.
The scan tool data values were taken from a known
good vehicle under the following conditions:
• The ignition switch is in the ON position.
• The engine is running at idle.
• The vehicle is in PARK.
• The doors are closed.
• The windows are closed.
• The A/C is ON, in UPPER mode.
• The ambient air temperatures are at 22-27°C (70-
80°F).
The HVAC Scan Tool Data Definitions contains a brief
description of all HVAC related parameters available on
the scan tool. 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.
BCM-Battery 1: The scan tool displays the level of
battery voltage at the BCM.
BCM-A/C Sensor:
BCM-Switch Inputs-A/C Request: The scan tool
displays On or Off. The BCM uses the A/C switch
input in order to determine if A/C compressor
operation is being requested by the HVAC control
module.
ECM-A/C Disengage: The scan tool displays the None,
A/C Pressure, Engine Speed, Batt Voltage, Anti Stall,
RPM Unstable, WOT, Launch Perf., Coolant Hot
disable of the a/c compressor.
Data List
Units Displayed
System Data
Inputs
Inactive/Active
Sensors
ECM-A/C High side Pressure Sensor: The scan tool
displays 0-3570 kPa (0-518 psi). This parameter
represents the high side pressure sensor voltage
signal converted to pressure.
ECM-A/C High Side Pressure Switch: The scan tool
displays the High Pressure/Normal status of the high
side pressure switch.
ECM-A/C Off for WOT: The scan tool displays the high
throttle disable of the a/c compressor.
ECM-A/C Off Due to Pressure: The scan tool displays
the status of the a/c high side pressure sensor. The
scan tool displays Active/Inactive.
ECM-A/C Auto Recirc: The scan tool displays the
status of the recirculation actuator.
ECM-A/C Relay Command: The scan tool displays On
or Off. On is displayed when the ECM has energized
the A/C clutch relay.
ECM-A/C Refrigerant Pressure: The scan tool
displays 0-4000 kPa (0-580 psi). This parameter
represents the A/C refrigerant pressure sensor
voltage signal converted to pressure.
ECM-A/C Refrigerant Pressure: The scan tool
displays 0 to 5 volts. The output of the A/C
refrigerant pressure sensor.
ECM-A/C Request: The scan tool displays Yes or No.
Yes is displayed when the BCM is requesting A/C
system operation.
ECM-ECT: The scan tool displays a range of 40-151°C
(40-304°F). The ECM applies 5 volts to the ECT
sensor circuit. The sensor is a thermistor which
changes internal resistance as the engine
temperature changes. When the sensor is cold,
internal resistance is high, the ECM senses 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
ECM interprets the lower voltage as a warm engine.
ECM-Ignition 1 Signal: The scan tool shows available
voltage at the ECM.
Typical Data Value
Off/On
Inactive
Counts
Off
Varies
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