Intermittent
Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.
HVAC Compressor Clutch Does Not Engage
| Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
| Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views DEFINITION: The A/C compressor clutch will not engage when an A/C request has been made and a Powertrain DTC has not been set. | ||||
| 1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | |
| 2 | Start the engine. Place the blower motor switch in the maximum speed position. Ensure the A/C OFF switch is not selected. Place the left air temperature switch in the coldest position. Does the A/C compressor operate? | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 3 | |
| 3 | Start the engine. Observe the coolant temperature indicator. Is the engine coolant temperature indicator illuminated? | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | Go to Step 4 | |
| 4 | Turn OFF the ignition. Install the ACR 2000. Record the ambient temperature at the vehicle. Record readings of the low and high side STATIC pressures. Compare the low and the high side pressure values with the allowable limits for the recorded ambient air temperature. Are the low and the high side pressure values within the allowable limits for the recorded ambient air temperature and are the pressure values within 103 kPa (15 psi) of each other? | Above 16°C (60°F) 345 kPa (50 psi) Above 24°C (75°F) 483 kPa (70 psi) Above 33°C (90°F) 690 kPa (100 psi) | Go to Step 5 | Go to Leak Testing in Heating, Ventilation and Air Conditioning |
| 5 | Install a scan tool. Turn ON the ignition, with the engine OFF. With a scan tool observe the A/C refrigerant pressure sensor in the engine control module (ECM) data list. Compare the A/C refrigerant pressure sensor parameter on the scan tool with the ACR 2000 high side pressure value. Is the scan tool A/C refrigerant pressure sensor parameter and the ACR 2000 pressure value within 15 psi of each other? | Go to Step 6 | Go to Step 14 | |
| 6 | With a scan tool, view the evaporator temperature in the HVAC system data. Is the evaporator temperature below 4°C (39F°)? | Go to Step 17 | Go to Step 7 | |
| 7 | With a scan tool, view the ambient air temperature in the HVAC system data. Is the ambient air temperature below 3°C (38F°)? | Go to Step 18 | Go to Step 8 | |
| 8 | Turn OFF the ignition. Disconnect the A/C compressor clutch. Turn ON the ignition, with the engine OFF. Probe the supply voltage circuit of the A/C compressor clutch with a test lamp that is connected to ground. With a scan tool, command the A/C compressor clutch relay ON. Does the test lamp illuminate? | Go to Step 9 | Go to Step 10 | |
| 9 | Test the ground circuit of the A/C compressor clutch for a high resistance or for an open. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 29 | Go to Step 13 | |
| 10 | Test the voltage supply circuit of the A/C compressor clutch for a high resistance or for an open. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 29 | Go to Step 11 | |
| 11 | Turn OFF the ignition. Disconnect the A/C compressor clutch relay. Turn ON the ignition, with the engine OFF. Probe the battery positive voltage circuit of the A/C compressor clutch relay with a test lamp that is connected to ground. Does the test lamp illuminate? | Go to Step 12 | Go to Step 25 | |
| 12 | Inspect for poor connections at the A/C compressor clutch relay. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 29 | Go to Step 26 | |
| 13 | Inspect for poor connections at the harness connector of the A/C compressor clutch. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 29 | Go to Step 27 | |
| 14 | Disconnect the A/C pressure sensor. With a test lamp connected to battery voltage, probe the ground circuit at the A/C pressure sensor connector. Does the test lamp illuminate? | Go to Step 19 | Go to Step 15 | |
| 15 | Test the ground circuit of the A/C refrigerant pressure sensor for a high resistance or for an open. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 29 | Go to Step 16 | |
| 16 | Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 29 | Go to Step 28 | |
| 17 | Inspect the evaporator temperature sensor circuits for high resistance. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 29 | Go to Step 21 | |
| 18 | Inspect the ambient air temperature sensor circuits for high resistance. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 29 | Go to Step 22 | |
| 19 | Inspect for poor connections at the harness connector of the A/C pressure sensor. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 29 | Go to Step 20 | |
| 20 | Replace the A/C refrigerant pressure sensor. Refer to Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement in Heating, Ventilation and Air Conditioning. Did you complete the replacement? | Go to Step 29 | ||
| 21 | Inspect for poor connections at the harness connector of the evaporator temperature sensor. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 29 | Go to Step 23 | |
| 22 | Inspect for poor connections at the harness connector of the ambient air temperature sensor. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 29 | Go to Step 24 | |
| 23 | Replace the evaporator temperature sensor. Refer to Evaporator Core Replacement in Heating, Ventilation and Air Conditioning. Did you complete the replacement? | Go to Step 29 | ||
| 24 | Replace the ambient air temperature sensor. Refer to Ambient Air Temperature Sensor Replacement . Did you complete the replacement? | Go to Step 29 | ||
| 25 | Repair the battery positive voltage circuit of the A/C compressor clutch relay. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 29 | ||
| 26 | Replace the A/C compressor clutch relay. Did you complete the replacement? | Go to Step 29 | ||
| 27 | Replace the A/C compressor clutch. Refer to Compressor Replacement (LY7) or Compressor Replacement (LH2) in Heating, Ventilation and Air Conditioning. Did you complete the replacement? | Go to Step 29 | ||
| 28 | Replace the HVAC control module. Refer to Control Module References in Computer/Integrating Systems for replacement, setup and programming. Did you complete the replacement? | Go to Step 29 | ||
| 29 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 2 | |
HVAC Compressor Clutch Does Not Engage
HVAC Compressor Clutch Does Not Disengage
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views DEFINITION: The A/C compressor clutch will not disengage when an A/C request has not been made and a Powertrain DTC has not been set. | |||
| 1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
| 2 | Start the engine. Place the A/C request switch in the OFF position. Is the A/C compressor clutch still engaged? | Go to Step 3 | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems |
| 3 | Turn OFF the ignition. Disconnect the A/C compressor clutch. Turn On the ignition, with the engine OFF. Probe the supply voltage circuit of the A/C compressor clutch with a test lamp that is connected to ground. Does the test lamp illuminate? | Go to Step 4 | Go to Step 6 |
| 4 | Test the supply voltage circuit of the A/C compressor clutch for a short to voltage. Refer to Circuit Testing and to Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 9 | Go to Step 5 |
| 5 | Inspect for poor connections at the A/C compressor clutch relay. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 9 | Go to Step 7 |
| 6 | Inspect for poor connections at the harness connector of the A/C compressor clutch. Refer to Testing for Intermittent Conditions and Poor Connections and to Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 9 | Go to Step 8 |
| 7 | Replace the A/C compressor clutch relay. Refer to Compressor Relay Replacement . Did you complete the replacement? | Go to Step 9 | |
| 8 | Replace the A/C compressor. Refer to Compressor Replacement (LY7) or Compressor Replacement (LH2) . Did you complete the replacement? | Go to Step 9 | |
| 9 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 3 |
HVAC Compressor Clutch Does Not Disengage
Blower Motor Always On
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views DEFINITION: The blower motor operates with the HVAC controls in the OFF position or the blower motor operates at high speed only. | |||
| 1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
| 2 | Turn ON the ignition, with the engine OFF. Turn OFF the HVAC control module. Is the blower motor OFF? | Go to Step 3 | Go to Step 8 |
| 3 | Turn ON the HVAC control module. Operate the blower motor switch from minimum to maximum. Does the blower motor only operate at high speed? | Go to Step 4 | Go to Blower Motor Malfunction |
| 4 | Turn OFF the ignition. Unplug the blower control processor. Turn ON the ignition. Turn ON the HVAC control module. With a test lamp connected to battery positive probe the blower motor speed control circuit. Operate the blower switch from minimum to maximum. Does the test lamp intensity change? | Go to Step 6 | Go to Step 5 |
| 5 | Test the blower motor speed control circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 11 | Go to Step 8 |
| 6 | Test the blower motor fan control circuit for a short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 11 | Go to Step 7 |
| 7 | Inspect for poor connections at the harness connector of the blower motor control processor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 11 | Go to Step 9 |
| 8 | Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 11 | Go to Step 10 |
| 9 | Replace the blower motor control processor. Refer to HVAC Control Processor Replacement . Did you complete the replacement? | Go to Step 11 | |
| 10 | Replace the HVAC control module. Refer to Control Module References in Computer/Integrating Systems for replacement, setup and programming. Did you complete the replacement? | Go to Step 11 | |
| 11 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 2 |
Blower Motor Always On
Blower Motor Inoperative
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views DEFINITION: The blower motor is inoperative in all speed positions. | |||
| 1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
| 2 | Turn ON the ignition, with the engine OFF. Place the blower motor switch in each speed position. Does the blower motor operate in any of the speed positions? | Go to Blower Motor Malfunction | Go to Step 3 |
| 3 | Turn OFF the ignition. Disconnect the blower motor connector. Turn ON the ignition, with the engine OFF. Turn ON the HVAC control module. Connect a test lamp between the blower motor supply voltage circuit and the blower motor fan control circuit. Place the blower motor switch in the maximum speed position. Does the test lamp illuminate? | Go to Step 14 | Go to Step 4 |
| 4 | Probe the supply voltage circuit of the blower motor with a test lamp that is connected to a good ground. Does the test lamp illuminate? | Go to Step 9 | Go to Step 5 |
| 5 | Turn OFF the ignition. Remove the blower motor relay. Test the battery positive voltage circuit on the switch side and the coil side of the relay connector with a test lamp connected to ground. Does the test lamp illuminate? | Go to Step 6 | Go to Step 17 |
| 6 | Turn ON the ignition, with the engine OFF. Turn ON the HVAC control module. Probe the blower motor relay control circuit with a test lamp that is connected to voltage. Does the test lamp illuminate? | Go to Step 7 | Go to Step 8 |
| 7 | Test the blower motor supply voltage circuit for an open, short to ground or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 22 | Go to Step 13 |
| 8 | Test the blower motor relay control circuit for an open, short to voltage or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 22 | Go to Step 16 |
| 9 | Turn OFF the ignition. Disconnect the blower motor control processor. Turn ON the ignition. Place the blower switch on high speed. Probe the blower motor speed control circuit with a test lamp connected to battery voltage. Does the test lamp illuminate? | Go to Step 11 | Go to Step 10 |
| 10 | Test the blower motor speed control circuit for an open, short to ground, short to voltage or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 22 | Go to Step 16 |
| 11 | Test the ground circuit of the blower motor control processor for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 22 | Go to Step 12 |
| 12 | Test the ground circuit between the blower motor and the blower motor control processor for an open, short to voltage or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 22 | Go to Step 15 |
| 13 | Inspect for poor connections at the harness connector of the blower motor relay. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 22 | Go to Step 18 |
| 14 | Inspect for poor connections at the harness connector of the blower motor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 22 | Go to Step 19 |
| 15 | Inspect for poor connections at the harness connector of the blower motor control processor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 22 | Go to Step 20 |
| 16 | Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 22 | Go to Step 21 |
| 17 | Repair the battery positive voltage circuit of the blower motor relay. Refer to Wiring Repairs in Wiring Systems. Did you complete the repair? | Go to Step 22 | |
| 18 | Replace the blower motor relay. Did you complete the replacement? | Go to Step 22 | |
| 19 | Replace the blower motor. Refer to Blower Motor Replacement in Heating, Ventilation and Air Conditioning. Did you complete the replacement? | Go to Step 22 | |
| 20 | Replace the blower motor control processor. Refer to HVAC Control Processor Replacement . Did you complete the replacement? | Go to Step 22 | |
| 21 | Replace the HVAC control module. Refer to Control Module References in Computer/Integrating Systems for replacement, setup and programming. Did you complete the replacement? | Go to Step 22 | |
| 22 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 2 |
Blower Motor Inoperative
Blower Motor Malfunction
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views DEFINITION: The blower motor operates in at least one speed position. | |||
| 1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
| 2 | Turn ON the ignition, with the engine OFF. Place the blower motor switch in each speed position. Does the blower motor operate at the desired speeds? | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 3 |
| 3 | Turn OFF the ignition. Disconnect the blower motor. Turn ON the ignition, with the engine OFF. Connect a test lamp between the blower motor supply voltage circuit and the blower motor fan control circuit of the blower motor. Place the blower motor switch from the minimum speed position to the maximum speed position. Does the test lamp illuminate and increase intensity? | Go to Step 9 | Go to Step 4 |
| 4 | Turn OFF the ignition. Disconnect the blower motor control processor. Turn ON the ignition, with the engine OFF. With a test lamp connected to battery voltage, probe the blower motor speed control circuit at the blower motor control processor. Place the blower motor switch from the minimum speed position to the maximum speed position. Does the test lamp illuminate and increase intensity? | Go to Step 6 | Go to Step 5 |
| 5 | Test the blower motor speed control circuit of the HVAC control module for high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 15 | Go to Step 11 |
| 6 | Test the battery positive voltage circuit of the blower motor control processor for a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 15 | Go to Step 7 |
| 7 | Test the ground circuit of the blower motor control processor for a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 15 | Go to Step 8 |
| 8 | Test the blower motor fan control circuit of the blower motor for a high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 15 | Go to Step 10 |
| 9 | Inspect for poor connections at the harness connector of the blower motor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 15 | Go to Step 12 |
| 10 | Inspect for poor connections at the harness connector of the blower motor control processor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 15 | Go to Step 13 |
| 11 | Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 15 | Go to Step 14 |
| 12 | Replace the blower motor. Refer to Blower Motor Replacement in Heating, Ventilation and Air Conditioning. Did you complete the replacement? | Go to Step 15 | |
| 13 | Replace the blower motor control processor. Refer to HVAC Control Processor Replacement . Did you complete the replacement? | Go to Step 15 | |
| 14 | Replace the HVAC control module. Refer to in Control Module References in Computer/Integrating Systems for replacement, setup and programming. Did you complete the replacement? | Go to Step 15 | |
| 15 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 2 |
Blower Motor Malfunction
Too Cold in Vehicle
| Step | Action | Values | Yes | No |
|---|---|---|---|---|
| Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views DEFINITION: The temperature cannot be adjusted, or heating is insufficient. | ||||
| 1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information | |
| 2 | Place the blower motor switch in each speed position. Does the blower motor operate in any speed position? | Go to Step 3 | Go to Blower Motor Inoperative | |
| 3 | Does the blower motor operate at the desired speeds? | Go to Step 4 | Go to Blower Motor Malfunction | |
| 4 | Install a scan tool. Turn ON the ignition, with the engine OFF. With a scan tool, command the water pump control ON in the climate control panel special functions, miscellaneous test. Does the after boil coolant pump operate? | Go to Step 5 | Go to After Boil Coolant Pump Inoperative in Engine Cooling | |
| 5 | Start the engine. Place the mode switch in the PANEL position. Place the recirculation switch in the ON position. Observe the recirculation door. Place the recirculation switch in the OFF position. Does the recirculation door move from the recirculation position to the outside air position? | Go to Step 6 | Go to Air Recirculation Malfunction | |
| 6 | Place the passenger temperature switch in the OFF position. Does the too cold in vehicle condition occur when heating or defrosting is desired? | Go to Step 7 | Go to Step 9 | |
| 7 | Start the engine. Turn OFF the HVAC controls. Does the A/C compressor operate? | Go to HVAC Compressor Clutch Does Not Disengage | Go to Step 8 | |
| 8 | Inspect the cooling system for the following conditions: A low coolant level A loose or worn accessory drive belt A leaking radiator hose or heater hose A kinked radiator hose or heater hose A missing radiator cap pressure seal A leaking radiator cap Refer to Heating Performance Diagnostic in Heating, Ventilation and Air Conditioning. Did you find and correct the condition? | Go to Step 25 | Go to Step 9 | |
| 9 | Place the mode switch in PANEL position. Turn ON the ignition, with the engine OFF. Place the blower motor switch in maximum speed position. Inspect for air flow through the inside air temperature sensor by placing a 5 cm (2 in) square piece of paper over the sensor air inlet. Does the paper stay in place? | Go to Step 10 | Go to Step 16 | |
| 10 | Install a thermometer near the inside air temperature sensor. With a scan tool, observe the Inside Air Temp parameter in the Climate Control Panel data list. Does the scan tool indicate the sensor temperatures is within 3°C (5°F) of the thermometer temperature? | Go to Step 11 | Go to Step 14 | |
| 11 | Turn OFF the ignition. Cover the sunload sensor. Turn ON the ignition. With a scan tool, observe the Driver and Passenger Solar Sensor parameter in the Climate Control Panel Open/Short data list. Is the Solar Sensor parameter greater than the specified value? | 220 Counts | Go to Step 12 | Go to Step 19 |
| 12 | Uncover the sunload sensor. Direct a light source at the sunload sensor. Observe the Driver and Passenger Sunload parameter. Do the counts change? | Go to Step 13 | Go to Step 19 | |
| 13 | Test the resistance of the ambient air temperature sensor. Refer to LINK 48912 . Is the resistance near the value in the Sensor Resistance Table? | Go to Testing for Intermittent Conditions and Poor Connections in Wiring Systems | Go to Step 15 | |
| 14 | Test the resistance of the inside air temperature sensor. Refer to LINK 48912 . Is the resistance near the value in the Sensor Resistance Table? | Go to Step 20 | Go to Step 18 | |
| 15 | Inspect for poor connections at the harness connector of the ambient air temperature sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 25 | Go to Step 17 | |
| 16 | Inspect the aspirator tube for a air leak or obstruction. Did you find and correct the condition? | Go to Step 25 | ||
| 17 | Inspect for poor connections at the harness connector of the ambient air temperature sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 25 | Go to Step 23 | |
| 18 | Inspect for poor connections at the harness connector of the inside air temperature sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 25 | Go to Step 21 | |
| 19 | Inspect for poor connections at the harness connector of the sunload sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 25 | Go to Step 22 | |
| 20 | Inspect for poor connections at the harness connector of the HVAC control module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 25 | Go to Step 24 | |
| 21 | Replace the inside air temperature sensor. Refer to Inside Air Temperature Sensor Replacement . Did you complete the replacement? | Go to Step 25 | ||
| 22 | Replace the sunload sensor. Refer to Sun Load Sensor Replacement . Did you complete the replacement? | Go to Step 25 | ||
| 23 | Replace the ambient air temperature sensor. Refer to Ambient Air Temperature Sensor Replacement . Did you complete the replacement? | Go to Step 25 | ||
| 24 | Replace the HVAC control module. Refer to Control Module References in Computer/Integrating Systems for replacement, setup, and programming. Did you complete the replacement? | Go to Step 25 | ||
| 25 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 2 | |
Too Cold in Vehicle
Exhaust Odor Inside Vehicle
| Step | Action | Yes | No |
|---|---|---|---|
| Schematic Reference: HVAC Schematics Connector End View Reference: HVAC Connector End Views | |||
| 1 | Did you perform the Diagnostic System Check - Vehicle? | Go to Step 2 | Go to Diagnostic System Check - Vehicle in Vehicle DTC Information |
| 2 | Install a scan tool. Turn ON the ignition, with the engine OFF. With a scan tool, observe the IPM Air Quality Sensitivity setting in the HVAC IPM Special Functions List. Does the scan tool indicate that the sensitivity level can be decreased? | Go to Step 3 | Go to Step 4 |
| 3 | Adjust the sensitivity level to decrease the sensitivity of the air quality sensor. Refer to Circuit Testing Operate the system in order to verify the condition. Did you correct the condition? | Go to Step 17 | Go to Step 4 |
| 4 | Turn OFF the ignition. Unplug the Air Quality Sensor. Turn ON the ignition, with the engine OFF. Turn ON the HVAC module. With a test lamp connected to battery voltage probe the ground circuit at the Air Quality Sensor connector. Does the test lamp illuminate? | Go to Step 5 | Go to Step 12 |
| 5 | With a test lamp connected to battery voltage probe the low reference circuit at the Air Quality Sensor connector. Does the test lamp illuminate? | Go to Step 6 | Go to Step 13 |
| 6 | With a test lamp connected to ground probe the ignition 1 voltage circuit at the Air Quality Sensor connector. Does the test lamp illuminate? | Go to Step 7 | Go to Step 14 |
| 7 | With a volt meter inspect the air quality Nox sensor signal circuit and the air quality HC sensor signal circuit at the Air Quality Sensor connector. Does the volt meter display near 5 volts or greater on either circuit? | Go to Step 8 | Go to Step 9 |
| 8 | Test the appropriate 5-volt sensor signal circuit of the Air Quality Sensor for a short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 17 | Go to Step 10 |
| 9 | Test the appropriate 5-volt sensor signal circuit of the Air Quality Sensor for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 17 | Go to Step 11 |
| 10 | Inspect for poor connections at the harness connector of the Air Quality Sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 17 | Go to Step 15 |
| 11 | Inspect for poor connections at the harness connector of the HVAC Control Module. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 17 | Go to Step 16 |
| 12 | Repair the ground circuit of the Air Quality Sensor for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 17 | |
| 13 | Repair the low reference circuit of the Air Quality Sensor for an open, high resistance or short to voltage. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 17 | |
| 14 | Repair the ignition 1 voltage circuit of the Air Quality Sensor for an open, high resistance or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems. Did you find and correct the condition? | Go to Step 17 | |
| 15 | Replace the Air Quality Sensor. Refer to Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement . Did you complete the replacement? | Go to Step 17 | |
| 16 | Replace the HVAC control module. Refer to Control Module References in Vehicle Control Systems for replacement, setup, and programming. Did you complete the replacement? | Go to Step 17 | |
| 17 | Operate the system in order to verify the repair. Did you correct the condition? | Go to Step 2 | System OK |
Exhaust Odor Inside Vehicle
Afterblow Enable Procedure
Afterblow is a feature that dries the evaporator core by operating the blower motor after the engine is turned off. This reduces the amount of microbial growth that can create undesirable odors. The vehicle does not come equipped with the afterblow feature turned on. If the afterblow feature is required due to an odor concern, it must be turned on by reprogramming the HVAC control module, refer to Service Programming System (SPS) in Programming and Setup.
After the HVAC control module has been programmed for afterblow, the following conditions must be met for afterblow to operate
- The engine has been turned off for at least 30 minutes.
- The ambient air temperature is at least 21°C (70°F).
- The A/C compressor operated for more than 2 minutes.
- The system voltage is at least 12 volts.
Once the above conditions have been met, the following sequence of events will occur
- The blower motor will run for 20 seconds.
- The blower motor will be off for 10 minutes.
- The blower motor will run for and additional 20 seconds.
HVAC Control Module
The HVAC control module is a class 2 device that interfaces between the operator and the HVAC system to maintain air temperature and distribution settings. The battery positive voltage circuit provides power that the control module uses for keep alive memory (KAM). The dash integration module (DIM), which is the vehicle power mode master, provides a device on signal. The control module supports the following features
| Feature | Availability |
|---|---|
| Afterblow | Available if reprogrammed by the technician |
| Purge | Yes |
| Personalization | Yes |
| Actuator Calibration | No |
| Heated Seat Control | Optional |
Air Delivery Description and Operation
The HVAC control module will receive information that defines the current driver of the vehicle from the driver door module (DDM) through class 2 communication. The HVAC system will memorize the following system configurations for up to 2 unique drivers
- Driver set temperature
- Passenger set temperature
- Mode
- Blower motor speed
- A/C compressor request, auto ON or A/C OFF
This information shall be stored inside the HVAC control module memory. When a different driver identification button is selected, the HVAC control module will recall the appropriate driver settings. When the HVAC control module is first turned on, the last stored settings for the current driver will be activated except for the rear defrost and heated seat settings.
Mode Actuator
The mode actuator is a 5-wire bi-directional electric motor that incorporates a feedback potentiometer. Low reference, 5-volt reference, position signal, and 2 control circuits enable the actuator to operate. The control circuits use either a 0 or 12-volt value to coordinate the actuator movement. When the actuator is at rest, both control circuits have a value of 0 volts. In order to move the actuator, the HVAC control module grounds one of the control circuits while providing the other with 12 volts. The HVAC control module reverses the polarity of the control circuits to move the actuator in the opposite direction. When the actuator shaft rotates, the potentiometers adjustable contact changes the door position signal between 0-5 volts. The HVAC control module uses a range of 0-255 counts to index the actuator position. The door position signal voltage is converted to a 0-255 count range. When the module sets a commanded, or targeted value, one of the control circuits is grounded. As the actuator shaft rotates, the changing position signal is sent to the module. Once the position signal and the commanded value are the same, the module removes power and ground from the control circuits.
Recirculation Actuator
The recirculation actuators are 5-wire bi-directional electric motors that incorporate a feedback potentiometer. Ignition 3 voltage, low reference, control, 5-volt reference and position signal circuits enable the actuators to operate. The control circuit uses either a 0, 2.5, or 5-volt signal to command the actuator movement. When the actuator is at rest, the control circuit value is 2.5 volts. A 0 or 5-volt control signal commands the actuator movement in opposite directions. When the actuator shaft rotates, the potentiometer's adjustable contact changes the door position signal between 0-5 volts.
Blower Motor Relay
The blower motor relay provides a supply voltage to the blower motor and blower motor control processor. The HVAC control module commands the blower motor relay ON anytime the commanded blower speed is not OFF.
Blower Motor Control Processor
The blower motor control processor is an interface between the HVAC control module and the blower motor. The blower motor speed control, blower motor supply voltage and ground circuits enable the control processor to operate. The HVAC control module provides a pulse width modulation (PWM) signal to the control processor in order to command the blower motor speed. The control processor uses the blower motor ground as a low side control to adjust the blower motor speed.
Air Speed
The blower motor forces air to circulate within the vehicle's interior. The vehicle operator determines the blower motors speed by placing the blower motor switch in a desired speed position or by selecting automatic operation. In manual operation, once a blower speed is selected, the blower speed remains constant, until a new speed is selected. In automatic operation, the HVAC control module will determine what blower speed is necessary in order to achieve or maintain a desired temperature.
As the requested blower speed increases, the following conditions occur
- The HVAC control module increases the amount of time that the blower motor speed control circuit is modulated to ground.
- The voltage and duty cycle, measured between the blower motor speed control circuit and ground, decrease.
As the requested blower speed decreases, the following conditions occur
- The HVAC control module decreases the amount of time that the blower motor speed control circuit is modulated to ground.
- The voltage and duty cycle, measured between the blower motor speed control circuit and ground, increase.
Afterblow
Afterblow is a feature that dries the evaporator core by operating the blower motor after the engine is turned OFF. This reduces the amount of microbial growth that can create undesirable odors. The vehicle does not come equipped with the afterblow feature turned ON. If the afterblow feature is required due to an odor concern, it must be turned ON by reprogramming the HVAC control module. Refer to Service Programming System (SPS) in Programming and Setup.
After the HVAC control module has been programmed for afterblow, the following conditions must be met for afterblow to operate
- The engine has been turned OFF for at least 30 minutes.
- The ambient air temperature is at least 21°C (70°F).
- The A/C compressor operated for more than 2 minutes before shut down.
- The system voltage is at least 12 volts.
Once the above conditions have been met, the following sequence of events will occur
- The blower motor will RUN for 20 seconds.
- The blower motor will be OFF for 10 minutes.
- The blower motor will RUN for and additional 20 seconds.
Steering Wheel Controls
The HVAC control module receives class 2 messages from the radio interface that the driver has activated a steering wheel control switch. The steering wheel control buttons control several different functions including the following HVAC functions
- Fan speed increase
- Fan speed decrease
- Driver set temperature increase
- Driver set temperature decrease
In order to configure the steering wheel controls, refer to Radio/Audio System Description and Operation in Entertainment.
Air Distribution
The HVAC control module controls the mode actuator in order to distribute airflow to a desired outlet. The mode switch provides the vehicle operator with the ability to override the automatic setting. When the mode door is moved to the defrost position, the A/C compressor clutch engages and the recirculation actuator will be moved to the outside air position. In the outside air position, the incoming air is filtered by the passenger compartment air filter.
| IMPORTANT | The HVAC system allows air to the outboard panel outlets in all air distribution modes. This allows air to be circulated higher in the cabin under any operating condition. The panel outlets have three operating positions, open, side window defogger and closed. To eliminate air from these outlets, the individual outlet thumbwheel must be turned to the OFF or side window defogger position. |
Recirculation
The HVAC control module controls the air intake through the recirculation actuator. Recirculation is not available when the mode is in defrost. When the mode is in defog, recirculation will only be available for 10 minutes. In the outside air position, the incoming air is filtered by the passenger compartment air filter.
Auxiliary HVAC Control Module
The auxiliary HVAC control module is a non-GM LAN device that interfaces between the operator and the auxiliary HVAC system to maintain air temperature and air distribution settings. Five volts and ground are supplied to the rear HVAC control module. The front HVAC control module monitors the position of the rear air temperature actuator and the rear mode actuator. The front HVAC module will move the actuators to the proper position when it receives a request from the rear HVAC control module on which position to place the actuator.
Auxiliary Air Distribution
The auxiliary HVAC control module provides airflow direction and temperature control for the back seat passengers. Passengers can operate the rear HVAC control module in both manual or automatic modes. Auxiliary HVAC mode positions can be set to OFF, VENT, FLOOR and VENT, or FLOOR positions. The front HVAC module provides power and ground to the auxiliary mode actuator. The front HVAC module receives power through the ignition 1 and battery positive voltage circuits from the underhood fuse block. The auxiliary mode actuator is a reverse polarity motor. Each circuit provides both power and ground to the auxiliary mode actuator. When the auxiliary mode actuator is being held in position, both of the auxiliary mode door control circuits have 0 volts applied to both sides of the actuator motor. This holds the actuator stationary. When a mode is selected, one of the auxiliary mode door control circuits will ground, driving the auxiliary mode actuator to the desired temperature. Depending on the mode that is requested, the other auxiliary air temperature door control circuit may ground. This moves the auxiliary mode actuator into the desired position.
Auxiliary Mode Actuator
The auxiliary mode actuator is a 5-wire bi-directional electric motor that incorporates a feedback potentiometer. Low reference, 5-volt reference, position signal, and 2 control circuits enable the actuator to operate. The control circuits use either a 0 or 12-volt value to coordinate the actuator movement. When the actuator is at rest, both control circuits have a value of 0 volts. In order to move the actuator, the HVAC control module grounds one of the control circuits while providing the other with 12 volts. The HVAC control module reverses the polarity of the control circuits to move the actuator in the opposite direction. When the actuator shaft rotates, the potentiometers adjustable contact changes the door position signal between 0-5 volts. The HVAC control module uses a range of 0-255 counts to index the actuator position. The door position signal voltage is converted to a 0-255 count range. When the module sets a commanded, or targeted value, one of the control circuits is grounded. As the actuator shaft rotates the changing position signal is sent to the module. Once the position signal and the commanded value are the same, the module removes power and ground from the control circuits.
The HVAC control module is a class 2 device that interfaces between the operator and the HVAC system to maintain air temperature and distribution settings. The battery positive voltage circuit provides power that the control module uses for keep alive memory (KAM). The dash integration module (DIM), which is the vehicle power mode master, provides a device on signal. The control module supports the following features
| Feature | Availability |
|---|---|
| Afterblow | Available if reprogrammed by the technician |
| Purge | Yes |
| Personalization | Yes |
| Actuator Calibration | No |
| Heated Seat Control | Optional |
Air Temperature Description and Operation
Remote Start and Personalization
If the remote start personalization feature for climate control is selected through radio, the HVAC control module will receive information that defines the current driver of the vehicle from the Ezkey module through GMLAN communication. This information shall be stored inside the HVAC control module memory. When a different key fob is selected, the HVAC control module will recall the appropriate driver settings. When the HVAC control module is first turned ON, the last stored settings for the current driver will be activated. Upon a battery reset, the HVAC control module shall also set the driver ID to Driver#2. The HVAC system will memorize the following system configurations for up to 2 unique drivers
- Driver set temperature
- Passenger set temperature
- Mode
- Blower motor speed
- A/C compressor request, auto ON or A/C OFF
OnStar® Blower Control ON/OFF
During OnStar® audio control ON, the HVAC control module receives signals from OnStar® to reduce blower level to a level 4. OnStar® blower control becomes active in auto or manual blower operation. During this OnStar® blower control, if in manual or auto blower, the display will show AUTO for blower display. This blower reduction is to ensure that all incoming and outgoing voice calls will be recognized by the OnStar® module. The driver is allowed to override the OnStar® auto blower level by increasing or decreasing it manually to any desired level. When OnStar® no longer sends the request for blower control the HVAC control module will cancel OnStar® blower control and resume previous blower level if no manual override of the blower was selected.
Air Temperature Actuators
The air temperature actuator is a 5-wire bi-directional electric motor that incorporates a feedback potentiometer. Low reference, 5-volt reference, position signal, and 2 control circuits enable the actuator to operate. The control circuits use either a 0 or 12-volt value to coordinate the actuator movement. When the actuator is at rest, both control circuits have a value of 0 volts. In order to move the actuator, the HVAC control module grounds one of the control circuits while providing the other with 12 volts. The HVAC control module reverses the polarity of the control circuits to move the actuator in the opposite direction. When the actuator shaft rotates, the potentiometers adjustable contact changes the door position signal between 0-5 volts. The HVAC control module uses a range of 0-255 counts to index the actuator position. The door position signal voltage is converted to a 0-255 count range. When the module sets a commanded, or targeted value, one of the control circuits is grounded. As the actuator shaft rotates the changing position signal is sent to the module. Once the position signal and the commanded value are the same, the module removes power and ground from the control circuits.
Air Temperature Sensors
The air temperature sensors are 2-wire negative temperature co-efficient thermistors. The vehicle uses the following air temperature sensors
- Ambient
- Inside
A signal and low reference circuit enables the sensor to operate. As the air temperature surrounding the sensor increases, the sensor resistance decreases. The sensor signal decreases as the resistance decreases. The sensor signal varies between 0-5 volts. The HVAC control module converts the signal to a range between 0-255 counts.
The inside temperature sensor operates within a temperature range between -6.5 to +57.5°C (+20.3 to +135.5°F). If the sensor is shorted to ground, voltage, or an open, the system will operate using an estimated default value to allow the system to operate. The ambient sensor operates within a temperature range between -30 to +51°C (-22 to +123.8°F). If the HVAC control module has determined that the ambient temperature sensor has failed, the driver information center (DIC) display shall display 59°F in place of the outside air temperature. If the sensor is shorted to ground, voltage, or an open, the system will operate using an estimated default value to allow the system to operate. If the engine coolant temperature is not more than 3°C (5.4°F) above the sensor reading, or if the engine has not been started in 3 hours, then the actual ambient air temperature sensor reading is displayed. Also at vehicle speeds greater than 35 km/h (22 mph), the ambient air temperature displayed may be allowed to increase, but only at a slow, filtered rate. The DIC displays the ambient air temperature value that it receives from the HVAC control module through a class 2 message. The ambient air temperature value can be updated by an outside air instant update feature.
To use this feature, press the following switches on the HVAC control module simultaneously
- AUTO
- MODE UP
- LEFT TEMPERATURE UP
Sunload Sensor
The sunload sensor is a 2-wire photo diode. The vehicle uses left and right sunload sensors. The 2 sensors are integrated into the sunload sensor assembly along with the ambient light sensor. Low reference and signal circuits enable the sensor to operate. As the sunload increases, the sensor signal decreases. The sensor operates within an intensity range between completely dark and bright. The sensor signal varies between 0-5 volts. The HVAC control module converts the signal to a range between 0-255 counts. The sunload sensor provides the HVAC control module a measurement of the amount of light shining on the vehicle. Bright or high intensity light causes the vehicle's inside temperature to increase. The HVAC system compensates for the increased temperature by diverting additional cool air into the vehicle. If the sensor is open or shorted, no sunload adjustment occurs and the SERVICE A/C SYSTEM message is displayed.
Evaporator Temperature Sensor
The HVAC control module monitors the temperature of the air passing through the evaporator by the A/C evaporator air temperature sensor. This sensor is located on the evaporator core. The temperature is used to cycle the A/C compressor ON and OFF to prevent the evaporator core from freezing. A thermistor inside the sensor varies its resistance to monitor the evaporator air temperature. The HVAC control module monitors the voltage drop across the thermistor when supplied with a 5-volt reference signal. The HVAC control module will send a class 2 message to the engine control module (ECM) to stop requesting the A/C compressor clutch operation if the temperature drops below 3°C (37°F). The sensor must be above 4°C (39°F) to request the A/C compressor clutch again.
The sensor operates within a temperature range between -40 to +215°C (-40 to +355°F). If the HVAC control module detects an open in the evaporator temperature sensor or circuit, the class 2 message sent to the ECM will not submit the A/C ON request. The HVAC control module will then send a request to the radio for display of the SERVICE A/C SYSTEM that will be displayed on the DIC. The HVAC control module will also display A/C OFF on the module as long as the condition is present.
A/C Refrigerant Pressure Sensor
The A/C refrigerant pressure sensor is a 3-wire piezoelectric pressure transducer. A 5-volt reference, low reference, and signal circuits enable the sensor to operate. The A/C pressure signal can be between 0-5 volts. When the A/C refrigerant pressure is low, the signal value is near 0 volts. When the A/C refrigerant pressure is high, the signal value is near 5 volts.
The A/C refrigerant pressure sensor prevents the A/C system from operating when an excessively high or low pressure condition exists.
If the ECM detects a failure in the A/C refrigerant pressure sensor or circuit, the class 2 message sent to the HVAC control module will be invalid. The HVAC control module will then send a request to the radio for display of the SERVICE A/C SYSTEM that will be displayed on the DIC. The HVAC control module will also display A/C OFF on the module as long as the condition is present.
Air Quality Sensor (RPO K14)
Warning - The air quality sensor recognizes carbon monoxide but is not designed as a safety feature to protect you from carbon monoxide. The air quality sensor is designed to limit your exposure to gasoline exhaust fumes and or diesel exhaust fumes that could enter into the passenger compartment from nearby vehicles for a limited amount of time. The HVAC control module monitors the outside air quality while in AUTO mode via the air quality sensor assembly. You can activate the air quality sensor on your vehicle, if equipped, by pressing the Auto button on the HVAC module. The air quality sensor is a 5-wire sensor, 1 ignition voltage circuit, 2 ground circuit, and 2 control circuits. There are 2 sensors inside the air quality sensor assembly. A hydro carbon (HC) sensor that is used for detecting gasoline exhaust fumes and a Nox sensor that is used for detecting nitrous oxide, diesel exhaust fumes. The HVAC control module outputs a 5-volt signal on the HC and Nox control circuits and operates in a range between 0-5 volts. The air quality sensor operates using an algorithm that can control the recirc actuator at any time when the HVAC module is in the AUTO mode. The algorithm is updated constantly because air quality from place to place can be very different and still considered normal for that area. The HVAC module updates the air quality sensor calibration approximately 4 times per second. The air quality sensor input to the HVAC module is compared to the previously updated air quality sensor calibration. If the voltage difference is great enough the recirc actuator will be controlled to recirc, outside air, or partial recirc outside air position based on the air quality sensor input. When air quality around the front of the vehicle is poor, the air quality sensor system operates as follows: Poor air quality with high HC levels will cause the HC control circuit to read a lower voltage. Poor air quality with high Nox levels will cause the Nox control circuit to read a higher voltage. The recirculation actuator is forced to the recirculation position. The recirc symbol on the HVAC module will illuminate. The recirc icon will not illuminate if the recirc actuator is already in the auto recirc position. When air quality around the front of the vehicle is normal, the air quality sensor system operates as follows: Normal air quality levels the HC control circuit will recognize very little voltage change from the previously updated calibration. Normal air quality levels the Nox control circuit will recognize very little voltage change from the previously updated calibration. The recirculation actuator position is not controlled by the air quality sensor system. The following are conditions that will prevent the air quality sensor from controlling the recirc actuator: A/C OFF conditions (compressor OFF) prevents air quality sensor from changing the current position of the actuator). Coolant temperature below 37°C (99°F) during warm up will prevent the blower from operating and air quality sensor from controlling the recirc position. Outside air temperature less than 5°C (41°F) (prevents air quality sensor from changing the current position of the actuator). Outside air temperature less than 15°C (59°F) and A/C high side pressure less than 196 kpa (28 psi) (prevents air quality sensor from changing the current position of the actuator). 28 seconds sensor warm-up time after ignition is turned ON (prevents air quality sensor from changing the current position of the actuator). Evaporator temperature sensor failure. Customer manually selects defrost or defog (forces actuator to outside air position). Customer manually selects recirc or outside air position. Coolant temperature above 112°C (V8), 119°C (HFV6) the actuator is forced to the recirc position. When coolant temperature drops below 109°C (V8), 116°C (HFV6) forced recirc is canceled. A/C pressure above 2 500 kpa (362 psi) the actuator is forces to the recirc position. When A/C pressure drops below 2 000 kpa (290 psi) forced recirc is canceled. The following describes the recirc actuator function after the air quality sensor has canceled the command to recirc. Full recirc position will be held for 2 minutes when vehicle speed is less than 10 km/h (6.3 mph). After 2 minutes expires the recirc door will move to full outside air position. Partial recirc, outside air position will be held for 2 minutes when vehicle speed is above 20 km/h (12.5 mph). After 2 minutes expires the recirc door will move to full outside air position. Full outside air position if vehicle speed is greater than 60 km/h (37 mph) and blower is not on high speed. The instrument panel module (IPM) shall provide the GMLAN Option Information for " Climate Air Quality Sensor Present" and "Climate Control Air Quality Sensitivity Selection" to the HVAC control module. Based on the option information received by the HVAC control module by the IPM during battery connect or sensitivity calibration setting change and ignition ON, the HVAC control module will choose 1 of 7 different sensitivity calibration settings stored in the HVAC module. The IPM sends the signal that tells the HVAC control module which sensitivity settings to use. The IPM sends a GMLAN message of 0 which tells the HVAC control module to use the default level 4 sensitivity calibration. The air quality sensitivity message sent to the HVAC module can be changed through the IPM with a TECH 2 and has 7 different air quality sensor calibration settings to choose from, 1 being the most sensitive to exhaust fumes and 7 being the least sensitive to exhaust fumes. The driver information center (DIC) will display the SERVICE A/C SYSTEM message if the HVAC system has detected a short to ground in the air quality sensor circuit. An open circuit or a short to voltage in the air quality sensor circuit will be diagnosed through symptom based diagnostics because both of these conditions will not turn on the SERVICE A/C SYSTEM message or set a trouble code.
The auxiliary HVAC control module is a non-GM LAN device that interfaces between the operator and the auxiliary HVAC system to maintain air temperature and air distribution settings. Five volts and ground are supplied to the rear HVAC control module. The front HVAC control module monitors the position of the rear air temperature actuator and the rear mode actuator. The front HVAC module will move the actuators to the proper position when it receives a request from the rear HVAC control module on which position to place the actuator.
Auxiliary Air Temperature Actuator
The auxiliary air temperature actuator is a 5-wire bi-directional electric motor that incorporates a feedback potentiometer. Low reference, 5-volt reference, position signal, and 2 control circuits enable the actuator to operate. The control circuits use either a 0 or 12-volt value to coordinate the actuator movement. When the actuator is at rest, both control circuits have a value of 0 volts. In order to move the actuator, the HVAC control module grounds one of the control circuits while providing the other with 12 volts. The HVAC control module reverses the polarity of the control circuits to move the actuator in the opposite direction. When the actuator shaft rotates, the potentiometers adjustable contact changes the door position signal between 0-5 volts. The HVAC control module uses a range of 0-255 counts to index the actuator position. The door position signal voltage is converted to a 0-255 count range. When the module sets a commanded, or targeted value, one of the control circuits is grounded. As the actuator shaft rotates, the changing position signal is sent to the module. Once the position signal and the commanded value are the same, the module removes power and ground from the control circuits.
The HVAC control module receives class 2 messages from the radio interface that the driver has activated a steering wheel control switch. The steering wheel control buttons can be reconfigured to control the following functions
- Fan speed increase
- Fan speed decrease
- Driver set temperature increase
- Driver set temperature decrease
In order to configure the steering wheel controls, refer to Radio/Audio System Description and Operation in Entertainment. The HVAC system interprets the fan and set temperature switches on the steering wheel as if the driver had activated the same switch function on the HVAC control module.
A/C Cycle
Refrigerant is the key element in an air conditioning system. R-134a is presently the only EPA approved refrigerant for automotive use. R-134a is a very low temperature gas that can transfer the undesirable heat and moisture from the passenger compartment to the outside air.
The Denso 7SBU16 variable displacement swash plate A/C compressor is belt driven and operates when the magnetic clutch is engaged. The compressor builds pressure on the vapor refrigerant. Compressing the refrigerant also adds heat to the refrigerant. The refrigerant is discharged from the compressor, through the discharge hose, and forced to flow to the condenser and then through the balance of the A/C system. The A/C system is mechanically protected with the use of a high pressure relief valve. If the high pressure switch were to fail or if the refrigerant system becomes restricted and refrigerant pressure continues to rise, the high pressure relief will pop open and release refrigerant from the system.
Compressed refrigerant enters the condenser in a high temperature, high pressure vapor state. As the refrigerant flows through the condenser, the heat of the refrigerant is transferred to the ambient air passing through the condenser. Cooling the refrigerant causes the refrigerant to condense and change from a vapor to a liquid state.
The condenser is located in front of the radiator for maximum heat transfer. The condenser is made of aluminum and aluminum cooling fins, which allow rapid heat transfer for the refrigerant. The semi-cooled liquid refrigerant exits the condenser and flows through the liquid line, to the thermal expansion valve.
The thermal expansion valve is located in the liquid line between the condenser and the evaporator. The thermal expansion valve is the dividing point for the high and the low pressure sides of the A/C system. As the refrigerant passes through the thermal expansion valve, the pressure of the refrigerant is lowered. Due to the pressure differential of the liquid refrigerant, the refrigerant will begin to vaporize at the thermal expansion valve. The thermal expansion valve also meters the amount of liquid refrigerant that can flow into the evaporator.
Refrigerant exiting the thermal expansion valve flows into the evaporator core in a low pressure, liquid state. Ambient air is drawn through the HVAC module and passes through the evaporator core. Warm and moist air will cause the liquid refrigerant boil inside of the evaporator core. The boiling refrigerant absorbs heat from the ambient air and draws moisture onto the evaporator. The refrigerant exits the evaporator back through the thermal expansion valve and into the suction line and back to the compressor, in a vapor state completing the A/C cycle of heat removal. At the compressor, the refrigerant is compressed again and the cycle of heat removal is repeated.
The conditioned air is distributed through the HVAC module for passenger comfort. The heat and moisture removed from the passenger compartment will also change form, or condense, and is discharged from the HVAC module as water under the vehicle.