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HVAC System - Manual Chevrolet Impala IX

Manual HVAC System 10 illustrations ~6124 words

Fastener Tightening Specifications

ApplicationSpecification
MetricEnglish
Heater and A/C Control Assembly Screw1.5 N.m13 lb in
Mode Actuator Screw1.5 N.m13 lb in
Recirculation Actuator Screw1.5 N.m13 lb in
Temperature Actuator - Left Screw1.5 N.m13 lb in
Temperature Actuator - Right Screw1.5 N.m13 lb in

Scheme 1

Scheme 1: HVAC Wiring Schematics
Scheme 1: HVAC Wiring Schematics

Scheme 2

Scheme 2
Scheme 2

Scheme 3

Scheme 3
Scheme 3

DIAGNOSTIC CODE INDEX

DTCDescription
DTC B0158B0158 13: Outside Air Temperature Sensor Circuit Voltage low B0158 14: Outside Air Temperature Sensor Circuit Voltage high
DTC B0223, B0233, B0248, B0268, B0408, B0418, or B0428B0223 04: Recirculate Position Command Circuit Open B0223 05: Recirculate Position Command Circuit Short to Battery or Open B0223 06: Recirculate Position Command Circuit Short to Ground or Open B0223 61: Recirculation Actuator Stuck B0233 04: Air Flow Control Circuit Open B0233 05: Air Flow Control Circuit Short to Battery or Open B0233 06: Air Flow Control Circuit Short to Ground or Open B0233 61: Air Flow Control Actuator Stuck B0408 04: Temperature Control 1 Circuit Open B0408 05: Temperature Control 1 Circuit Short to Battery or Open B0408 06: Temperature Control 1 Circuit Short to Ground or Open B0408 61: Temperature Control 1 Circuit Actuator Stuck B0418 04: Temperature Control 2 Circuit Open B0418 05: Temperature Control 2 Circuit Short to Battery or Open B0418 06: Temperature Control 2 Circuit Short to Ground or Open B0418 61: Temperature Control 2 Circuit Actuator Stuck
DTC P0532 or P0533P0532: Air Conditioning A/C Refrigerant Pressure Sensor Circuit Low Voltage P0533: Air Conditioning A/C Refrigerant Pressure Sensor Circuit High Voltage
DTC P0645P0645: Air Conditioning (A/C) Clutch Relay Control Circuit

DIAGNOSTIC CODE INDEX

Diagnostic Instructions

  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/impala/ix-2006-2016/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/impala/ix-2006-2016/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/impala/ix-2006-2016/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Diagnostic Fault Information

CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Ambient Air Temperature Sensor SignalB0158 13B0158 13B0158 14B0158 13,14
Low ReferenceB0158 14B0158 13B0158 13,14

Circuit/System Description

The HVAC control module supplies the ambient air temperature sensor with a low reference circuit and 5-volt signal circuit. The HVAC control module determines the voltage drop across the sensor, which is proportional to temperature. As the air temperature increases, the sensor resistance decreases and the voltage signal decreases. As the air temperature decreases, the sensor resistance increases and the voltage signal increases.

Conditions for Running the DTC

The ignition is turned ON.

Conditions for Setting the DTC

The HVAC control module detects the ambient air temperature sensor signal circuit is less than -36°C (-38°F) or more than 215°C (419°F) for more than 15 seconds.

Action Taken When the DTC Sets

  1. The HVAC control module will display dashes for outside air temperature.
  2. The DIC will display SERVICE A/C SYSTEM.
  3. The system operates using a default value.

Conditions for Clearing the DTC

  1. The DTC will become history if the HVAC control module no longer detects the condition that set the DTC.
  2. The history DTC will clear after 50 fault-free ignition cycles.

Reference Information

Schematic Reference

Connector End View Reference

Description and Operation

  1. «Air Delivery Description and Operation»(/chevrolet/impala/ix-2006-2016/remont/manual-hvac-system/#hvac-system-manual__air-delivery-description-and-operation)
  2. «Air Temperature Description and Operation»(/chevrolet/impala/ix-2006-2016/remont/manual-hvac-system/#hvac-system-manual__air-temperature-description-and-operation)

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/impala/ix-2006-2016/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/impala/ix-2006-2016/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/impala/ix-2006-2016/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/impala/ix-2006-2016/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Testing

IMPORTANTAn instant OAT update must be performed by pressing the A/C and Recirc buttons at the same time after the system has been repaired to convert the A/C permission from out of range to normal.
  1. Ignition OFF, disconnect the harness connector at the outside air temperature sensor.
  2. Ignition OFF, test for less than 10 ohms of resistance between the low reference circuit terminal B and ground. If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the HVAC control module.
  3. Ignition ON, verify the scan tool Ambient Air Temperature sensor parameter is less than -35°F (-37°C). If greater than the specified range, test the signal circuit terminal A for a short to ground. If the circuit tests normal, replace the HVAC control module.
  4. Install a 3A fused jumper wire between the signal circuit terminal A and the low reference circuit terminal B. Verify the scan tool Ambient Air Temperature sensor parameter is greater than 180°F (82°C). If less than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the HVAC control module.
  5. If all circuits test normal, test or replace the ambient air temperature sensor.

Repair Procedures

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Ambient Air Temperature Sensor Replacement»(/chevrolet/impala/ix-2006-2016/remont/manual-hvac-system/#hvac-system-manual)
  2. «Control Module References»(/chevrolet/impala/ix-2006-2016/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for HVAC control module replacement, setup and programming
  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/impala/ix-2006-2016/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/impala/ix-2006-2016/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/impala/ix-2006-2016/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Recirculate Position Command Circuit AB0223 04, 06B0223 04, 06B0223 05, 06B0223 61
Recirculate Position Command Circuit BB0223 04, 06B0223 04, 06B0223 05, 06B0223 61
Mode Door Control Circuit AB0233 04, 06B0233 04, 06B0233 05, 06B0233 61
Mode Door Control Circuit BB0233 04, 06B0233 04, 06B0233 05, 06B0233 61
Driver Air Temperature Door Control A CircuitB0408 04, 06B0408 04, 06B0408 05, 06B0408 61
Driver Air Temperature Door Control B CircuitB0408 04, 06B0408 04, 06B0408 05, 06B0408 61
Passenger Air Temperature Door Control A CircuitB0418 04, 06B0418 04, 06B0418 05, 06B0418 61
Passenger Air Temperature Door Control B CircuitB0418 04, 06B0418 04, 06B0418 05, 06B0418 61

The actuator is an electronic stepper motor. The HVAC control module supplies power and ground to the actuator. The HVAC control module controls the direction of the actuator by changing the polarity of the control circuits. When the actuator reaches its desired position, both circuits are fixed to the same value 0 volts. The HVAC control module determines the door position by counting pulses, voltage fluctuations, caused by the brush to commutator action generated during normal motor operation. The HVAC control module monitors a voltage drop across an internal resistance to detect the pulses. The HVAC control module converts the pulses to counts with a range of 0-255 counts.

  1. The ignition is ON.
  2. Ignition voltage is between 9-16 volts.
  3. The HVAC module is ON.

The actual door position differs from the commanded door position by more than 4 counts or the HVAC control module detects the door position signal circuit is shorted to ground shorted to voltage or open.

Driver A and driver B circuits are deactivated for the appropriate actuator.

  1. The DTC becomes history when the HVAC control module no longer detects the condition that set the DTC.
  2. The history DTC will clear after 50 fault-free ignition cycles.
  3. The DTC can be cleared with a scan tool.

Schematic Reference

Connector End View Reference

Description and Operation

  1. «Air Delivery Description and Operation»(/chevrolet/impala/ix-2006-2016/remont/manual-hvac-system/#hvac-system-manual__air-delivery-description-and-operation)
  2. «Air Temperature Description and Operation»(/chevrolet/impala/ix-2006-2016/remont/manual-hvac-system/#hvac-system-manual__air-temperature-description-and-operation)

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/impala/ix-2006-2016/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/impala/ix-2006-2016/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/impala/ix-2006-2016/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/impala/ix-2006-2016/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition OFF, disconnect the harness connector at the appropriate actuator.
  2. Ignition ON, connect a test lamp between the control circuit terminal A and control circuit terminal B or terminal C for the mode actuator. Command the actuator in each direction. The test lamp should briefly illuminate when commanding the actuator in one direction to the other direction. If the test lamp is always OFF, test the appropriate control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the HVAC control module. If the test lamp continuously illuminates, test the appropriate control circuit for a short to B+. If the circuit tests normal, replace the HVAC control module.
  3. If all circuits test normal, replace the appropriate actuator.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Air Inlet Valve Actuator Replacement»(/chevrolet/impala/ix-2006-2016/remont/manual-hvac-system/#hvac-system-manual)
  2. «Mode Valve Actuator Replacement (Impala)»(/chevrolet/impala/ix-2006-2016/remont/manual-hvac-system/#hvac-system-manual)
  3. «Temperature Valve Actuator Replacement - Left Side»(/chevrolet/impala/ix-2006-2016/remont/manual-hvac-system/#hvac-system-manual)
  4. «Temperature Valve Actuator Replacement - Right Side»(/chevrolet/impala/ix-2006-2016/remont/manual-hvac-system/#hvac-system-manual)
  5. «Control Module References»(/chevrolet/impala/ix-2006-2016/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for HVAC control module setup, replacement, and programming
  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/impala/ix-2006-2016/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/impala/ix-2006-2016/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/impala/ix-2006-2016/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to Voltage
5-Volt Reference CircuitP0532P0532P0533
A/C Refrigerant Pressure Sensor Signal CircuitP0532P0533P0532
Low Reference CircuitP0532P0533

The engine control module (ECM) monitors the high side refrigerant pressure through the A/C refrigerant pressure sensor. The ECM supplies a 5-volt reference and a low reference to the sensor. Changes in the A/C refrigerant pressure cause the A/C refrigerant pressure sensor signal to the ECM to vary. When the pressure is low, the signal voltage is low. When the pressure is high, the ECM commands the cooling fans on. When pressure is too high or too low, the ECM will not allow the A/C compressor clutch to engage.

The Engine is running.

  1. The ECM detects that the A/C pressure is less than 1 psi (0.01 volt).
  2. The ECM detects that the A/C pressure is more than 425 psi (4.90 volts).
  1. The ECM will not illuminate the malfunction indicator lamp (MIL).
  2. The ECM stores the failure records.
  3. The A/C compressor clutch is disabled.
  1. The history DTC will clear after 40 consecutive ignition cycles have occurred without a malfunction.
  2. The DTC will become history if the ECM no longer detects a failure.

Diagnostic Aids

A malfunction within the refrigerant system causing high pressure can cause this DTC to set.

Schematic Reference

Connector End View Reference

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/impala/ix-2006-2016/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/impala/ix-2006-2016/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/impala/ix-2006-2016/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/impala/ix-2006-2016/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

Ignition ON, observe the scan tool A/C Refrigerant Pressure Sensor parameter. The reading should be between 0.1 volt (1 psi) and 4.90 volts (425 psi) and change with A/C refrigerant pressure changes.

  1. Ignition OFF, disconnect the harness connector at the A/C refrigerant pressure sensor.
  2. Ignition OFF, test for less than 10 ohms between the low reference circuit terminal 1 and ground. If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the PCM.
  3. Ignition ON, test for 4.8-5.2 volts between the 5-volt reference circuit terminal 2 and ground. If less than the specified range, test the 5-volt reference circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the PCM. If greater than the specified range, test the 5-volt reference circuit for a short to voltage. If the circuit tests normal, replace the PCM.
  4. Verify the scan tool A/C High Side Pressure Sensor parameter is less than 0.1 volts (1 psi). If greater than the specified range, test the signal circuit terminal 3 for a short to voltage. If the circuit tests normal, replace the PCM.
  5. Install a 3A fused jumper wire between the signal circuit terminal 3 and the 5-volt reference circuit terminal 2. Verify the scan tool A/C Refrigerant High Side Pressure Sensor parameter is greater than 4.90 volts (425 psi). If less than the specified range, test the signal circuit for short to ground or an open/high resistance. If the circuit tests normal, replace the PCM.
  6. If all circuits test normal, test or replace the A/C refrigerant pressure sensor.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement»(/chevrolet/impala/ix-2006-2016/remont/automatic-hvac-system/#heating-ventilation-and-air-conditioning)
  2. «Control Module References»(/chevrolet/impala/ix-2006-2016/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for the ECM replacement, setup, and programming
  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/impala/ix-2006-2016/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/impala/ix-2006-2016/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/impala/ix-2006-2016/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
A/C Relay Coil Ignition22
A/C Relay Switch B+22
A/C Relay ControlP0645P0645P0645
A/C Clutch Control221
A/C Compressor Clutch Ground22
1. A/C Clutch Always Engaged 2. A/C Clutch Inoperative

Circuit Description

When the A/C switch is pressed, the HVAC control assembly sends a GMLAN message to the engine control module (ECM) for an A/C request. This input will request the ECM to ground the A/C compressor clutch relay control circuit, which will switch the A/C CMPRSR relay. With the relay contacts closed, battery voltage is supplied to the A/C compressor clutch assembly.

  1. The ignition voltage is between 11-18 volts.
  2. The engine speed is less than 600 RPM.
  3. The ECM driver transitions from ON to OFF or from OFF to ON.

Conditions for Setting the DTCs

The ECM detects an open on the control circuit of the A/C compressor clutch relay when commanded off with the engine in crank or run status.

The ECM will store conditions which were present when the DTC set as Failure Records data only. This information will not be stored as Freeze Frame data.

  1. A History DTC clears after 40 consecutive warm-up cycles have occurred without a malfunction.
  2. The DTC can be cleared by using a scan tool.

Schematic Reference

Connector End View Reference

Description and Operation

  1. «Air Delivery Description and Operation»(/chevrolet/impala/ix-2006-2016/remont/manual-hvac-system/#hvac-system-manual__air-delivery-description-and-operation)
  2. «Air Temperature Description and Operation»(/chevrolet/impala/ix-2006-2016/remont/manual-hvac-system/#hvac-system-manual__air-temperature-description-and-operation)

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/impala/ix-2006-2016/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/impala/ix-2006-2016/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/impala/ix-2006-2016/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/impala/ix-2006-2016/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition OFF, disconnect the A/C CMPRSR relay.
  2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal 86 and ground. If the test lamp illuminates, test the control circuit for a short to ground.
  3. Verify that a test lamp illuminates between the ignition circuit terminal 85 and ground. If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal and ignition circuit fuse is open, test or replace the relay.
  4. Connect a test lamp between the ignition circuit terminal 85 and thecontrol circuit terminal 86.
  5. Command the A/C relay ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states. If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the ECM. If the test lamp is always OFF, test the control circuit for a short to voltage, or an open/high resistance. If the circuit tests normal, replace the ECM.
  6. If all circuits test normal, test or replace the A/C CMPRSR relay.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Control Module References»(/chevrolet/impala/ix-2006-2016/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for ECM replacement, setup, and programming
  2. «Relay Replacement (Attached to Wire Harness)»(/chevrolet/impala/ix-2006-2016/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-repair-instructions) or «Relay Replacement (Within an Electrical Center)»(/chevrolet/impala/ix-2006-2016/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-repair-instructions)

Symptoms - HVAC Systems - Manual

IMPORTANTReview the system operation in order to familiarize yourself with the system functions. Refer to: Air Delivery Description and Operation Air Temperature Description and Operation

Visual/Physical Inspection

  1. Inspect for aftermarket devices which could affect the operation of the HVAC System. Refer to «Checking Aftermarket Accessories»(/chevrolet/impala/ix-2006-2016/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__checking-aftermarket-accessories) .
  2. Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.
  3. Verify the A/C compressor clutch turns freely and is not seized.
  4. The A/C compressor will not operate in cold outside air temperatures. Refer to «Air Temperature Description and Operation»(/chevrolet/impala/ix-2006-2016/remont/manual-hvac-system/#hvac-system-manual__air-temperature-description-and-operation) .
  5. The following conditions may cause window fogging: Wet carpet or mats High humidity Interior water leak Blocked A/C evaporator drain tube Maximum passenger capacity Blocked body pressure relief valves
  6. Inspect the air distribution system for causes of reduced air flow: Obstructed or dirty passenger compartment air filter, if equipped Blocked or damaged air inlet or outlet vents

Intermittent

Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections .

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom

  1. «Air Conditioning Compressor Malfunction»(/chevrolet/impala/ix-2006-2016/remont/manual-hvac-system/#hvac-system-manual)
  2. «Blower Motor Malfunction»(/chevrolet/impala/ix-2006-2016/remont/manual-hvac-system/#hvac-system-manual)
  3. «Ambient Air Temperature Malfunction»(/chevrolet/impala/ix-2006-2016/remont/manual-hvac-system/#hvac-system-manual)
  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/impala/ix-2006-2016/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/impala/ix-2006-2016/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/impala/ix-2006-2016/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
A/C Relay Coil Ignition22
A/C Relay Switch B+22
A/C Relay ControlP0645P0645P0645
A/C Clutch Control221
A/C Compressor Clutch Ground22
1. A/C Clutch Always Engaged 2. A/C Clutch Inoperative

When the A/C switch is pressed, the HVAC control module grounds the A/C request signal circuit. This input will request the ECM to ground the A/C compressor clutch relay control circuit, which will switch the A/C CMPRSR relay. With the relay contacts closed, battery voltage is supplied to the A/C compressor clutch assembly.

The following conditions must be met in order for the ECM to turn on the compressor clutch

  1. Battery voltage is between 9-18 volts.
  2. Engine coolant temperature (ECT) is less than 123°C (253°F).
  3. Engine speed is less than 4760 RPM.
  4. Engine speed is more than 600 RPM.
  5. A/C high side pressure is between 2929-269 kPa (425-39 psi).
  6. Throttle position is less than 100 percent.
  7. Evaporator temperature is greater than 0°C (32°F)
  8. ECM does not detect excessive torque load
  9. ECM does not detect insufficient idle quality.

Schematic Reference

Connector End View Reference

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/impala/ix-2006-2016/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/impala/ix-2006-2016/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/impala/ix-2006-2016/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/impala/ix-2006-2016/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition OFF, disconnect the A/C CMPRSR relay.
  2. Ignition ON, verify that a test lamp does not illuminate between the control circuit terminal and ground. If the test lamp illuminates, test the control circuit for a short to voltage.
  3. Verify that a test lamp illuminates between the ignition circuit terminal and ground. If the test lamp does not illuminate, test the ignition circuit for a short to ground or an open/high resistance. If the circuit tests normal and the ignition circuit fuse is open, test or replace the A/C CMPRSR relay.
  4. Verify that a test lamp illuminates between the B+ circuit terminal and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse is open, test the control circuit terminal for a short to ground.
  5. Disconnect the harness connector at the A/C compressor clutch.
  6. Test for less than 1.0 ohm of resistance between the A/C compressor clutch ground circuit terminal A and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
  7. Connect the harness connector at the A/C compressor clutch.
  8. Connect a 10A fused jumper wire between the B+ circuit terminal and the control circuit terminal. Verify the A/C compressor clutch is activated. If the A/C compressor clutch does not activate, test the control circuit for an open/high resistance. If the circuit tests normal, test or replace the A/C compressor clutch.
  9. Connect a test lamp between the ignition circuit terminal and the control circuit terminal.
  10. Command the A/C relay ON and OFF with a scan tool. The test lamp should turn ON and OFF when changing between the commanded states. If the test lamp is always ON, test the control circuit for a short to ground. If the circuit tests normal, replace the ECM. If the test lamp is always OFF, test the control circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the ECM.
  11. If all circuits test normal, test or replace the A/C CMPRSR relay.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Air Conditioning Clutch Assembly Replacement»(/chevrolet/impala/ix-2006-2016/remont/automatic-hvac-system/#heating-ventilation-and-air-conditioning)
  2. «Air Conditioning Compressor Replacement (LZE, LGD)»(/chevrolet/impala/ix-2006-2016/remont/automatic-hvac-system/#heating-ventilation-and-air-conditioning)
  3. «Control Module References»(/chevrolet/impala/ix-2006-2016/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for HVAC control module and ECM replacement, setup and programming
  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/impala/ix-2006-2016/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/impala/ix-2006-2016/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/impala/ix-2006-2016/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Blower Motor Speed Control Circuit at the Blower Motor Control Processor1, 211, 2
Battery Positive Voltage Circuit at the Blower Motor Control Processor1
Ground Circuit of the Blower Motor Control Processor1
Blower Motor Low Reference Circuit (between motor and control processor)1
1. Blower Motor Inoperative 2. Blower Motor Always On

Blower Motor Control Processor

The blower motor control module is an interface between the HVAC control module and the blower motor. The blower motor speed control, battery positive and ground circuits enable the control module to operate. The HVAC control module provides a variable voltage signal to the blower motor control module to request the selected blower speed. The blower motor control module provides a pulse width modulation (PWM) ground signal to the blower motor in order to control the blower motor speed. The module supplies 12 volts to the blower motor through the blower motor voltage supply circuit.

Be sure the blower motor housing is not shorted to a grounded surface causing the blower motor to always be on in high speed.

Schematic Reference

Connector End View Reference

Description and Operation

  1. «Air Delivery Description and Operation»(/chevrolet/impala/ix-2006-2016/remont/manual-hvac-system/#hvac-system-manual__air-delivery-description-and-operation)
  2. «Air Temperature Description and Operation»(/chevrolet/impala/ix-2006-2016/remont/manual-hvac-system/#hvac-system-manual__air-temperature-description-and-operation)

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/impala/ix-2006-2016/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/impala/ix-2006-2016/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/impala/ix-2006-2016/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/impala/ix-2006-2016/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition OFF, disconnect the harness connector at the blower motor control module.
  2. Test for less than 1.0 ohm between the ground circuit terminal A and ground. If greater than the specified range, test the ground circuit for an open/high resistance.
  3. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal C and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal and the B+ circuit fuse (BATT 4 30-amp) in the underhood fuse block is open, test all components connected to the B+ circuit and replace as necessary.
  4. Connect a DMM between the control circuit terminal B and B+.
  5. Cycle the blower motor from OFF to HIGH. The voltage should increase while changing between the commanded states. If voltage remains greater than 11.5V while changing between the commanded states, test the control circuit for a short to voltage. If the circuit test normal, replace the HVAC control module. If voltage remains less than 1.0V while changing between the commanded states, test the control circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the HVAC control module. If voltage is between 1.0V or 11.5V and does not increase when changing between the commanded states, replace the HVAC control module.
  6. Ignition OFF, reconnect the harness connector at the blower motor control module. Disconnect the harness connector at the blower motor.
  7. Ignition ON, verify that a test lamp illuminates between the B+ circuit terminal A of the blower motor control module and ground. If the test lamp does not illuminate, test the B+ circuit for a short to ground or an open/high resistance. If the circuit tests normal, replace the blower motor control module.
  8. Connect a test lamp between the control circuit terminal B and the B+ circuit terminal A.
  9. Turn the blower motor on high speed then to low speed. The test lamp intensity should be bright when in high speed and very dim or off when the blower is on low speed. If the test lamp intensity does not vary, test the control circuit for a short to voltage, short to ground, or an open/high resistance. If the circuit tests normal, replace the blower motor control module.
  10. If all circuits test normal, test or replace the blower motor.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Blower Motor Control Module Replacement»(/chevrolet/impala/ix-2006-2016/remont/automatic-hvac-system/#heating-ventilation-and-air-conditioning)
  2. «Blower Motor Replacement»(/chevrolet/impala/ix-2006-2016/remont/automatic-hvac-system/#heating-ventilation-and-air-conditioning)
  3. «Control Module References»(/chevrolet/impala/ix-2006-2016/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for ECM, and HVAC control module setup, replacement, and programming
  1. Perform the «Diagnostic System Check - Vehicle»(/chevrolet/impala/ix-2006-2016/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/chevrolet/impala/ix-2006-2016/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__strategy-based-diagnosis) for an overview of the diagnostic approach.
  3. «Diagnostic Procedure Instructions»(/chevrolet/impala/ix-2006-2016/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Ambient Air Temperature Sensor Signal211
Ambient Air Temperature Low Reference11
1. Too hot in vehicle condition 2. Temperature display inaccurate

The HVAC control module supplies the ambient air temperature sensor with a low reference circuit and signal circuit. The HVAC control module determines the voltage drop across the sensor, which is proportional to temperature. As the air temperature increases, the sensor resistance decreases and the voltage signal decreases. As the air temperature decreases, the sensor resistance increases and the voltage signal increases.

Schematic Reference

Connector End View Reference

Description and Operation

  1. «Air Delivery Description and Operation»(/chevrolet/impala/ix-2006-2016/remont/manual-hvac-system/#hvac-system-manual__air-delivery-description-and-operation)
  2. «Air Temperature Description and Operation»(/chevrolet/impala/ix-2006-2016/remont/manual-hvac-system/#hvac-system-manual__air-temperature-description-and-operation)

Electrical Information Reference

  1. «Circuit Testing»(/chevrolet/impala/ix-2006-2016/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/chevrolet/impala/ix-2006-2016/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/chevrolet/impala/ix-2006-2016/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures)
  4. «Wiring Repairs»(/chevrolet/impala/ix-2006-2016/remont/ignition-switchsteering-lock/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

IMPORTANTAn instant OAT update must be performed by pressing the A/C and Recirc buttons at the same time after the system has been repaired to convert the A/C permission from out of range to normal.
  1. Ignition OFF, disconnect the harness connector at the outside air temperature sensor.
  2. Ignition OFF, test for less than 10 ohms of resistance between the low reference circuit terminal B and ground. If greater than the specified range, test the low reference circuit for an open/high resistance. If the circuit tests normal, replace the HVAC control module.
  3. Ignition ON, verify the scan tool Ambient Air Temperature sensor parameter is less than -35°F (-37°C). If greater than the specified range, test the signal circuit terminal A for a short to ground. If the circuit tests normal, replace the HVAC control module.
  4. Install a 3A fused jumper wire between the signal circuit terminal A and the low reference circuit terminal B. Verify the scan tool Ambient Air Temperature sensor parameter is greater than 180°F (82°C). If less than the specified range, test the signal circuit for a short to voltage or an open/high resistance. If the circuit tests normal, replace the HVAC control module.
  5. If all circuits test normal, test or replace the ambient air temperature sensor.

Perform the Diagnostic Repair Verification after completing the diagnostic procedure.

  1. «Control Module References»(/chevrolet/impala/ix-2006-2016/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for HVAC control module replacement, setup and programming
  2. «Ambient Air Temperature Sensor Replacement»(/chevrolet/impala/ix-2006-2016/remont/manual-hvac-system/#hvac-system-manual)

Calibration Procedure

Use the following steps to perform the calibration update

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Select HVAC Control Module
  4. Select Special Functions
  5. Select recalibrate All Motors
  6. Select ON, wait 60 seconds.

Scheme 4

Scheme 4: Heater and Air Conditioning Control Replacement
Scheme 4: Heater and Air Conditioning Control Replacement
CalloutComponent Name
Preliminary Procedure: Remove the accessory trim plate. Refer to Instrument Panel Accessory Trim Plate Replacement .
1Heater and A/C Control Assembly Screw (Qty: 2) CAUTION: Refer to Fastener Caution . Tip: Disconnect the HVAC control assembly electrical connector. Tighten: 1.5 N.m (13 lb in)
2Heater and Air Conditioning Control Assembly Refer to Control Module References for programming and setup information.
CAUTION
Refer to Fastener Caution .

Scheme 5

Scheme 5: Temperature Valve Actuator Replacement - Right Side
Scheme 5: Temperature Valve Actuator Replacement - Right Side
CalloutComponent Name
Preliminary Procedure Remove the instrument panel (I/P) compartment inner panel. Refer to Instrument Panel Compartment Inner Panel Replacement . Disconnect the right air temperature actuator electrical connector.
1Temperature Actuator Screw - Right (Qty: 2) CAUTION: Refer to Fastener Caution . Tighten: 1.5 N.m (13 lb in)
2Temperature Actuator - Right Tip: Refer to Control Module References for programming and setup information.
CAUTION
Refer to Fastener Caution .

Scheme 6

Scheme 6: Temperature Valve Actuator Replacement - Left Side
Scheme 6: Temperature Valve Actuator Replacement - Left Side
CalloutComponent Name
Preliminary Procedure Remove the left knee bolster bracket. Refer to Driver Knee Bolster Bracket Replacement . Disconnect the left air temperature actuator electrical connector.
1Temperature Actuator Screw - Left (Qty: 2) CAUTION: Refer to Fastener Caution . Tighten: 1.5 N.m (13 lb in)
2Temperature Actuator - Left Tip: Refer to Control Module References for programming and setup information.
CAUTION
Refer to Fastener Caution .

Scheme 7

Scheme 7: Mode Valve Actuator Replacement (Impala)
Scheme 7: Mode Valve Actuator Replacement (Impala)
CalloutComponent Name
Preliminary Procedure Remove the instrument panel (I/P) inner panel. Refer to Instrument Panel Compartment Inner Panel Replacement . Disconnect the mode actuator electrical connector.
1Mode Actuator Screw (Qty: 2) CAUTION: Refer to Fastener Caution . Tighten: 1.5 N.m (13 lb in)
2Mode Actuator Tip: Refer to Control Module References for programming and setup information.
CAUTION
Refer to Fastener Caution .

Scheme 8

Scheme 8: Air Inlet Valve Actuator Replacement
Scheme 8: Air Inlet Valve Actuator Replacement
CalloutComponent Name
Preliminary Procedure Remove the right closeout panel. Refer to Instrument Panel Insulator Panel Replacement - Right Side . Disconnect the recirculation actuator electrical connector.
1Recirculation Actuator Screw (Qty: 2) CAUTION: Refer to Fastener Caution . Tighten: 1.5 N.m (13 lb in)
2Recirculation Actuator Tip: Refer to Control Module References for programming and setup information.
CAUTION
Refer to Fastener Caution .

Scheme 9

Scheme 9: Ambient Air Temperature Sensor Replacement
Scheme 9: Ambient Air Temperature Sensor Replacement
CalloutComponent Name
Preliminary Procedure: Remove the upper radiator air baffle. Refer to Radiator Air Upper Baffle and Deflector Replacement .
1Ambient Air Temperature Sensor Assembly

Air Delivery Description and Operation

The air delivery controls are divided into 4 areas

  1. HVAC Control Components
  2. Air Speed
  3. Air Distribution
  4. Recirculation Operation

HVAC Control Module

The HVAC control module is a GMLAN 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). If the battery positive voltage circuit loses power, all HVAC DTCs and settings will be erased from KAM. The control module supports the following features

FeatureAvailability
AfterblowOptional
PurgeNo
PersonalizationNo
Actuator CalibrationYes

Mode/Recirculation Actuator

The mode/recirculation actuator is a 2 wire bi-directional electric motor. Two 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 the appropriate control circuit for the commanded direction. The HVAC control module reverses the polarity of the control circuits to move the actuator in the opposite direction.

The HVAC control module determines the door position by counting motor pulses on one of the control circuits. These pulses are small voltage fluctuations that occur when the brush is shorted across 2 commutator contacts as the motor rotates. As the actuator shaft rotates, the HVAC control module monitors the voltage drop across an internal resistance to detect the pulses. The HVAC control module converts the pulses to counts with a range of 0-255 counts. The HVAC control module uses a range of 0-255 counts to index the actuator position.

Mode Valve Assembly

The film valve system has several operating characteristics

  1. The cycle time for a mode change will vary based on the starting point of the film valve relative to the requested mode position.
  2. The maximum time to achieve a mode change occur when the film valve travels between vent and defrost.
  3. Mode change times may very slightly based on variations in system airflow, temperature and voltage.
  4. The amount of air rush noise heard when a mode change is requested that causes the film valve to move through 3 or more primary modes is dependent on blower speed.
  5. Recalibration will typically occur when the engine is OFF. The actuator noise heard during recalibration may be more noticeable than during normal operation.

The blower motor control module is an interface between the HVAC control module and the blower motor. The blower motor speed control, battery positive and ground circuits enable the control module to operate. The HVAC control module provides a variable voltage signal to the blower motor control module to request the selected blower speed. The blower motor control module provides a pulse width modulation (PWM) ground signal to the blower motor in order to control the blower motor speed. The module supplies 12 volts to the blower motor through the blower motor voltage supply circuit.

Air Speed

The blower motor forces air to circulate within the vehicles interior. The vehicle operator determines the blower motors speed by placing the blower motor switch in a desired speed position. The blower motor will only operate if the blower motor switch is in any position other than OFF, and the ignition switch is in the RUN position, with the exception of afterblow.

Once a blower speed is selected, the blower speed remains constant, until a new speed is selected. When OnStar® System is activated the blower speed will be reduced.

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 following conditions must be met for afterblow to operate

  1. The A/C compressor operated for more than 15 minutes.
  2. The system voltage is at least 11 volts to start and 10 volts to continue to run.
  3. The ignition has been in the OFF position for at least 20 minutes.
  4. The outside air temperature is greater than 11°C (52°F).

Once the above conditions have been met, the blower will turn ON for 5 minutes and run at 30 percent blower speed.

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 switch is moved to heater through Defrost positions, the A/C compressor clutch engages and the recirculation actuator will be moved to the Outside Air position. When VENT is pressed, the following will occur

  1. The mode valve will be moved to the Panel position.
  2. The recirculation actuator will follow user request if the blower is ON and the power mode is in Run.
  3. The A/C compressor will follow user request if the blower is ON and the power mode is in Run.

Recirculation Operation

The HVAC control module controls the air intake through the recirculation actuator. Recirculation is not available when the mode is in heater through defrost. The recirculation LED will flash 3 times indicating recirculation is not available. The operator must activate the blower for Recirculation operation. The A/C compressor will engage while in the recirculation position. Every time the vehicle or HVAC system is turned off, the system will default to outside air unless the mode is in heater through defrost position.

Remote Start Activation

The following describes the HVAC control head functionality upon receiving the remote start active serial data message and a power mode status is set to off/awake. The OAT sensor on manual systems, is utilized to determine the moding of the following features: Blower Mode (Bi-level, Floor, Defrost, Recirc and Rear Defrost. These features are determined by the OAT during activation sequence and are maintained for the duration of engine run time. Calibratable temperatures are utilized to provide low, mid and high temperature ranges for the selectable feature. Blower and mode have the range to select any valid feature positions. When the remote start active serial data is received, ignition-OFF loop HVAC algorithms will act the same as if a run power mode was received, i.e. re-calibration, afterblow, ignition-OFF motor positioning etc. The OFF timer and the ignition ON timer have the functionality as in the Run mode.

Remote Start De-activation

When the remote start is exited, GMLAN power mode equals run mode or remote start engine. In the case of manual settings, the displays will revert to the actual state of operation of the features, on the basis of their normal control algorithms.

Air Temperature Description and Operation

The air temperature controls are divided into 4 areas

  1. HVAC Control Components
  2. Heating and A/C Operation
  3. Engine Coolant
  4. A/C Cycle

The HVAC control module is a GMLAN 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). If the battery positive voltage circuit loses power, all HVAC DTCs and settings will be erased from KAM. The control module supports the following features

FeatureAvailability
AfterblowOptional
PurgeNo
PersonalizationNo
Actuator CalibrationYes

Air Temperature Actuator

The air temperature actuator is a 2-wire bi-directional electric motor. Two control circuits enable the actuator to operate. The control circuits use either a 0-volt 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 the appropriate control circuit for the commanded direction. The HVAC control module reverses the polarity of the control circuits to move the actuator in the opposite direction.

The HVAC control module determines the door position by counting motor pulses on one of the control circuits. These pulses are small voltage fluctuations that occur when the brush is shorted across 2 commutator contacts as the motor rotates. As the actuator shaft rotates, the HVAC control module monitors the voltage drop across an internal resistance to detect the pulses. The HVAC control module converts the pulses to counts with a range of 0-255 counts. The HVAC control module uses a range of 0-255 counts to index the actuator position.

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 protects the A/C system from operating when an excessively high or low pressure condition exists. The powertrain control module (PCM) disables the compressor clutch under the following conditions

  1. A/C pressure is more than 3034 kPa (440 psi). The clutch will be enabled after the pressure decreases to less than 2068 kPa (300 psi).
  2. A/C pressure is less than 241 kPa (35 psi). The clutch will be enabled after the pressure increases to more than 248 kPa (36 psi).

Outside Air Temperature Sensor

The air temperature sensor is a 2-wire negative temperature co-efficient thermistor. 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 ambient sensor operates within a temperature range between -30 to +51°C (-22 to +123.8°F). The driver information center (DIC) displays the ambient air temperature that it receives from the HVAC control module through a GMLAN message. If the HVAC control module has determined that the ambient temperature sensor has failed the DIC will display 86°C (186°F) if shorted to ground and -40°C (-40°F) if open or shorted to voltage.

The HVAC module controls the temperature displayed on the DIC and the instant update feature as follows

ConditionDisplay
When the HVAC module A/C and RECIRCULATION buttons are pressed simultaneously.Updates temperature display instantly.
At start up with the engine OFF more than 3 hoursDisplays actual outside temperature
At start up with the engine OFF less than 3 hoursDisplays last stored temperature unless temperature has decreased. The temperature reading is always instantly up dated if ambient air temperature has decreased.
Vehicle moving above 16 km/h (10 mph) for 5 minutesUpdates temperature display at a slow filtered rate.
Vehicle moving at 51 km/h (32 mph) or greater for 2.5 minutesUpdates temperature display rapidly.
When the ambient air decreases.Updates temperature display rapidly.

Heating and A/C Operation

The purpose of the heating and A/C system is to provide heated and cooled air to the interior of the vehicle. The A/C system will also remove humidity from the interior and reduce windshield fogging. The vehicle operator can determine the passenger compartment temperature by adjusting the air temperature switch. Regardless of the temperature setting, the following can affect the rate that the HVAC system can achieve the desired temperature

  1. Recirculation actuator setting
  2. Difference between inside and desired temperature
  3. Difference between ambient and desired temperature
  4. Blower motor speed setting
  5. Mode setting

The A/C system can be engaged by either pressing the A/C switch or by selecting the following modes

  1. Max A/C
  2. Heater
  3. Mix-Blend
  4. Front Defrost

The A/C LED will not illuminate unless the driver presses the A/C request switch on the HVAC control module. Otherwise, the A/C system may be running without the A/C LED indicator illuminated while in Defrost mode. The following conditions must be met in order for the powertrain control module (PCM) to turn ON the compressor clutch

  1. The ambient air temperature is above 4°C (40°F).
  2. The engine coolant temperature (ECT) is less than 124°C (255°F).
  3. The A/C pressure is between 241-3034 kPa (35-440 psi).

Once engaged, the compressor clutch will be disengaged for the following conditions

  1. The throttle position is 100 percent.
  2. The A/C pressure is more than 3034 kPa (440 psi).
  3. The A/C pressure is less than 241 kPa (35 psi).
  4. The engine coolant temperature (ECT) is more than 124°C (255°F).
  5. The engine speed is more than 5480 RPM for at least 409 seconds.
  6. A transmission shift has occurred.
  7. The PCM detects excessive torque load.
  8. The PCM detects insufficient idle quality.
  9. The PCM detects a hard launch condition.
  10. Outside air temperature is detected to be below 38° F by the OAT sensor if equipped.
  11. The blower switch is turned OFF.

When the A/C compressor clutch is disengaged for any of these reasons, the A/C indicator LED will flash indicating A/C is not functioning. When the compressor clutch disengages, the compressor clutch diode protects the electrical system from a voltage spike.

The following describes the HVAC control head functionality upon receiving the remote start active serial data message and a power mode status is set to OFF/awake. Outside ambient temperature, is utilized to determine the moding of the following features: Blower Mode (Bi-level, Floor, Defrost, Recirc and Rear Defrost. These features are determined by the OAT during activation sequence and are maintained for the duration of engine run time. Calibratable temperatures are utilized to provide low, mid and high temperature ranges for the selectable feature. Blower and mode have the range to select any valid feature positions. When the remote start active serial data is received, ignition-OFF loop HVAC algorithms will act the same as if a run power mode was received, i.e. re-calibration, afterblow, ignition-OFF motor positioning etc. The OFF timer and the ignition ON timer have the functionality as in the Run mode.

When the remote start is exited, class 2 power mode equals run mode or remote start engine. In the case of manual settings, the displays will revert to the actual state of operation of the features, on the basis of their normal control algorithms.

Special Tools

Illustration Tool Number/ Description J 43600 ACR 2000 Air Conditioning Service Center

Scheme 10

Scheme 10: Special Tools
Scheme 10: Special Tools