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HVAC System - Automatic Cadillac SRX II рестайлинг

Automatic HVAC System 25 illustrations ~17483 words

Fastener Tightening Specifications

ApplicationSpecification
MetricEnglish
Temperature Valve Actuator Screw1.5 N.m13 lb in
Heater and Blower and Air-conditioning Control Module Screw1.5 N.m13 lb in
Air Inlet Valve Actuator Screw1.5 N.m13 lb in
Mode Control Cam Actuator Screw1.5 N.m13 lb in
Inside Air Valve Actuator Screw1.5 N.m13 lb in

Fastener Tightening Specifications

Scheme 46

Scheme 46: Power, Ground, Data Communication, and Blower Controls
Scheme 46: Power, Ground, Data Communication, and Blower Controls

Scheme 47

Scheme 47: A/C Compressor Controls
Scheme 47: A/C Compressor Controls

Scheme 48

Scheme 48: Sensors
Scheme 48: Sensors

Scheme 49

Scheme 49: Temperature Sensors
Scheme 49: Temperature Sensors

Scheme 50

Scheme 50: Mode and Temperature Controls - Front
Scheme 50: Mode and Temperature Controls - Front

Scheme 51

Scheme 51: Mode and Temperature Controls - Rear (CJ4)
Scheme 51: Mode and Temperature Controls - Rear (CJ4)

HVAC Component Replacement Reference

Component Code / Schematic NameRepair Instruction Name
A20 Radio/HVAC ControlsRadio Control Assembly Replacement
B1 A/C Refrigerant Pressure SensorAir Conditioning (A/C) Refrigerant Pressure Sensor Replacement
B108 Air Quality SensorAmbient Air Quality Sensor Replacement
B10B Ambient Light/Sunload Sensor
B39 A/C Evaporator Temperature SensorEvaporator Air Temperature Sensor Replacement
B7C Air Temperature Sensor - Duct Lower AuxiliaryDuct Air Temperature Sensor Replacement - Lower
B7D Air Temperature Sensor - Duct Left LowerDuct Air Temperature Sensor Replacement - Lower Left Side
B7E Air Temperature Sensor - Duct Right LowerDuct Air Temperature Sensor Replacement - Lower Right Side
B7G Air Temperature Sensor - Duct Upper AuxiliaryDuct Air Temperature Sensor Replacement - Upper
B7H Air Temperature Sensor - Duct Left UpperDuct Air Temperature Sensor Replacement - Upper Left Side
B7J Air Temperature Sensor Duct-Right UpperDuct Air Temperature Sensor Replacement - Upper Right Side
K33 HVAC Control ModuleHeater and Air Conditioning Control Replacement
K33A HVAC Control Module - AuxiliaryHeater and Air Conditioning and Radio Control Module Replacement
K8 Blower Motor Control ModuleHeater and Blower and Air Conditioning Control Module Replacement
K8A Blower Motor Control Module - AuxiliaryAuxiliary Heater and Air Conditioning Control Module Replacement
M37 Mode Door ActuatorMode Control Cam Actuator Replacement
M37B Mode Door Actuator - AuxiliaryAuxiliary Mode Valve Actuator Replacement
M46 Air Recirculation Door ActuatorAir Inlet Valve Actuator Replacement - Left Side , or Air Inlet Valve Actuator Replacement - Right Side
M6B Air Temperature Door Actuator - AuxiliaryAuxiliary Temperature Valve Actuator Replacement
M6L Air Temperature Door Actuator - LeftTemperature Valve Actuator Replacement - Left Side
M6R Air Temperature Door Actuator - RightTemperature Valve Actuator Replacement - Right Side
M8 Blower MotorBlower Motor Replacement
M8B Blower Motor - AuxiliaryAuxiliary Blower Motor Replacement
Q2 A/C Compressor ClutchAir Conditioning Compressor Replacement (LFX)
Q46 A/C Compressor Solenoid ValveAir Conditioning Compressor Replacement (LFX)

HVAC Component Replacement Reference

Diagnostic Code Index

DTCDescription
DTC B0163, B0183, or B1405DTC B0163 Passenger Compartment Temperature Sensor Circuit DTC B0183 Solar Load Sensor Circuit DTC B1405 Control Module Voltage Reference Output 2 Circuit
DTC B0173, B0178, B0509, B0514, B0519, B3583, or B3933DTC B0173 02 Upper Left Duct Air Temperature Sensor Circuit Short to Ground DTC B0173 05 Upper Left Duct Air Temperature Sensor Circuit High Voltage/Open DTC B0178 02 Lower Left Duct Air Temperature Sensor Circuit Short to Ground DTC B0178 05 Lower Left Duct Air Temperature Sensor Circuit High Voltage/Open DTC B0509 02 Upper Right Duct Air Temperature Sensor Circuit Short to Ground DTC B0509 05 Upper Right Duct Air Temperature Sensor Circuit High Voltage/Open DTC B0514 02 Lower Right Duct Air Temperature Sensor Circuit Short to Ground DTC B0514 05 Lower Right Duct Air Temperature Sensor Circuit High Voltage/Open DTC B0519 02 Rear Upper Duct Air Temperature Sensor Circuit Short to Ground DTC B0519 05 Rear Upper Duct Air Temperature Sensor Circuit High Voltage/Open DTC B3583 02 Rear Lower Duct Air Temperature Sensor Circuit Short to Ground DTC B3583 05 Rear Lower Duct Air Temperature Sensor Circuit High Voltage/Open DTC B3933 02 Air Conditioning Evaporator Temperature Sensor Circuit Short to Ground DTC B3933 05 Air Conditioning Evaporator Temperature Sensor Circuit High Voltage/Open
DTC B018A, B048C, B048F, or B1395DTC B018A Windshield Temperature Sensor Circuit DTC B048C Humidity Sensor Humidity Circuit DTC B048F Humidity Sensor Temperature Circuit DTC B1395 Control Module Voltage Reference Output Circuit
DTC B0193DTC B0193 01 Front Blower Motor Speed Circuit Short to Battery DTC B0193 06 Front Blower Motor Speed Circuit Low Voltage/Open
DTC B0208DTC B0208 01 Rear Blower Motor Speed Circuit Short to Battery DTC B0208 06 Rear Blower Motor Speed Circuit Low Voltage/Open
DTC B0223, B022A, B0233, B023A, B0408, B0418, B0428, or B3531DTC B0223 01 Recirculate Position Command 1 Circuit Short to Battery DTC B0223 06 Recirculate Position Command 1 Circuit Low Voltage/Open DTC B022A 01 Recirculate Position Command 2 Circuit Short to Battery DTC B022A 06 Recirculate Position Command 2 Circuit Low Voltage/Open DTC B0233 01 Air Flow Control Circuit Short to Battery DTC B0233 06 Air Flow Control Circuit Low Voltage/Open DTC B023A 02 HVAC Actuators Supply Voltage Short to Ground DTC B0408 01 Main Temperature Control Circuit Short to Battery DTC B0408 06 Main Temperature Control Circuit Low Voltage/Open DTC B0418 01 Right Temperature Control Circuit Short to Battery DTC B0418 06 Right Temperature Control Circuit Low Voltage/Open DTC B0428 01 Rear Temperature Control Circuit Short to Battery DTC B0428 06 Rear Temperature Control Circuit Low Voltage/Open DTC B3531 01 Rear Air Flow Control Circuit Short to Battery DTC B3531 06 Rear Air Flow Control Circuit Low Voltage/Open
DTC B1020DTC B1020 39 Auxiliary Electronic Control Unit (ECU) Internal Malfunction
DTC B3843DTC B3843 02 Air Quality Sensor Circuit Short to Ground DTC B3843 05 Air Quality Sensor Circuit High Voltage/Open DTC B3843 08 Air Quality Sensor Circuit Performance - Signal Invalid
DTC B393BDTC B393B Air Conditioning Compressor Valve Control Circuit
DTC P0532 or P0533DTC P0532 Air Conditioning (A/C) Refrigerant Pressure Sensor Circuit Low Voltage DTC P0533 Air Conditioning (A/C) Refrigerant Pressure Sensor Circuit High Voltage
DTC P0645, P0646, or P0647DTC P0645 Air Conditioning (A/C) Compressor Clutch Relay Control Circuit DTC P0646 Air Conditioning (A/C) Compressor Clutch Relay Control Circuit Low Voltage DTC P0647 Air Conditioning (A/C) Compressor Clutch Relay Control Circuit High Voltage

DIAGNOSTIC CODE INDEX

Diagnostic Instructions

  1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/srx/ii-2012-2016/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/cadillac/srx/ii-2012-2016/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»(/cadillac/srx/ii-2012-2016/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

DTC Descriptors

For symptom byte information, refer to Symptom Byte List .

Diagnostic Fault Information

CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
Temperature SignalB0163 02B0163 05B0163 051
Sunload SignalB0183 05B0183 02B0183 021
Clock SignalB1405 02B1405 05B1405 051
Low ReferenceB0163 05, B0183 05
1. HVAC Malfunction

Circuit/System Description

The ambient light/sunload sensor integrates the sunload and passenger compartment temperature functions within a single assembly.

The solar sensor uses 4 unique circuits as detailed below

  1. Low reference circuit - This is a common ground for the ambient light/sunload sensor assembly.
  2. Temperature signal circuit - This is the signal circuit for the temperature sensor.
  3. Clock signal circuit - This has 2 functions, via a high side PWM signal, the HVAC control module supplies power to the sensor as well as a clock input for the sensor microprocessor.
  4. Sunload signal circuit - This is used as an output from the solar sensor to the HVAC control module to transmit sun heat (IR) intensity, elevation, and azimuth data.

The passenger compartment temperature sensor is a negative temperature coefficient thermistor. As the air temperature increases, the sensor resistance decreases. The sensor signal varies between 0-5 V.

Bright or high intensity light causes the vehicles interior temperature to increase. The automatic HVAC system compensates for the increased temperature by diverting additional cool air into the vehicle.

Conditions for Running the DTC

  1. Ignition ON
  2. The HVAC control module is ON.

Conditions for Setting the DTC

B0163 02

The input signal is out of range. The HVAC control module detects voltage less than 0.1 V on the temperature signal circuit.

B0163 05

The input signal is out of range. The HVAC control module detects voltage greater than 4.9 V on the temperature signal circuit.

B0183 02

The input signal is out of range. The HVAC control module detects voltage less than 0.1 V on the solar sensor signal circuit.

B0183 05

The input signal is out of range. The HVAC control module detects voltage greater than 4.9 V on the solar sensor signal circuit.

B1405 02

The input signal is out of range. The HVAC control module detects voltage less than 10 V on the clock/power supply circuit.

B1405 05

The input signal is out of range. The HVAC control module detects a short to voltage or an open the clock/power supply circuit.

Action Taken When the DTC Sets

B0163 02, B0163 05, B0183 02, B0183 05

The system will use the last valid values as a default.

B1405 02, B1405 05

If no value is read at the time of fault, the HVAC control module uses 0 W/m 2 as intensity.

Conditions for Clearing the DTC

The condition for setting the DTC is no longer present.

Reference Information

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Circuit/System Verification

  1. Verify DTCs B0163 and B0183 are not both set concurrently. If both DTCs are set Refer to «Low Reference Test»(/cadillac/srx/ii-2012-2016/remont/automatic-hvac-system/#hvac-system-automatic__circuitsystem-testing) . If both DTCs are not set
  2. Verify DTC B0163, B0183, or B1405 is not set. If one of the DTCs is set Refer to the appropriate diagnostic in Circuit/System Testing (below). If none of the DTCs are set
  3. Verify the B10B Ambient Light/Sunload Sensor is accurate. If the sensor is not accurate Perform the following Circuit/System Testing in the order listed below: Circuit/System Testing - Low Reference Test Circuit/System Testing - DTC B0163 Circuit/System Testing - DTC B1405 Circuit/System Testing - DTC B0183 If the sensor is accurate
  4. All OK.

Circuit/System Testing

Low Reference Test

  1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the B10B Ambient Light/Sunload Sensor. It may take up to 10 min for all vehicle systems to power down.
  2. Test for less than 10 ohms between the low reference circuit terminal 6 and ground. If 10 ohms or greater Ignition OFF, disconnect the harness connector at the K33 HVAC Control Module. Test for less than 2 ohms in the low reference circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, replace the K33 HVAC Control Module. If less than 10 ohms
  3. Test or replace the B10B Ambient Light/Sunload Sensor.

DTC B0163

  1. Ignition OFF, disconnect the harness connector at the B10B Ambient Light/Sunload Sensor, ignition ON.
  2. Verify the scan tool Passenger Compartment Air Temperature (Unfiltered) parameter is less than -37°C (-35°F). If -37°C (-35°F) or greater Ignition OFF, disconnect the harness connector at the K33 HVAC Control Module. Test for infinite resistance between the signal circuit terminal 3 and ground. If less than infinite resistance, repair the short to ground on the circuit. If infinite resistance, replace the K33 HVAC Control Module. If less than -37°C (-35°F)
  3. Install a 3 A fused jumper wire between the signal circuit terminal 3 and the low reference circuit terminal 6.
  4. Verify the scan tool parameter Passenger Compartment Air Temperature (Unfiltered) parameter is greater than 78°C (172°F). If 78°C (172°F) or less Ignition OFF, remove the jumper wire and disconnect the harness connector at the K33 HVAC Control Module, ignition ON. Test for less than 1 V between the signal circuit and ground. If 1 V or greater, repair the short to voltage on the circuit. If less than 1 V Ignition OFF. Test for less than 2 ohms in the signal circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, replace the K33 HVAC Control Module. If greater than 78°C (172°F)
  5. Test or replace the B10B Ambient Light/Sunload Sensor.

DTC B0183

  1. Ignition OFF, disconnect the harness connector at the B10B Ambient Light/Sunload Sensor, ignition ON.
  2. Test for 4.8-5.2 V between the signal circuit terminal 4 and ground. If less than 4.8 V Ignition OFF, disconnect the harness connector at the K33 HVAC Control Module. Test for infinite resistance between the signal circuit and ground. If less than infinite resistance, repair the short to ground on the circuit. If infinite resistance Test for less than 2 ohms in the signal circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, replace the K33 HVAC Control Module. If greater than for 5.2 V Ignition OFF, disconnect the harness connector at the K33 HVAC Control Module, ignition ON. Test for less than 1 V between the signal circuit and ground. If 1 V or greater, repair the short to voltage on the circuit. If less than 1 V, replace the K33 HVAC Control Module. If between 4.8-5.2 V
  3. Test or replace the B10B Ambient Light/Sunload Sensor.
  4. Verify DTC B0183 did not reset. If DTC B0183 reset Replace the K33 HVAC Control Module. If DTC B0183 did not reset
  5. All OK.

DTC B1405

  1. Ignition OFF, disconnect the harness connector at the B10B Ambient Light/Sunload Sensor, ignition ON.
  2. Test for greater than 10 V between signal circuit terminal 2 and ground. If less than 10 V Ignition OFF, disconnect the harness connector at the K33 HVAC Control Module. Test for infinite resistance between signal circuit terminal 2 and ground. If less than infinite resistance, repair the short to ground on the circuit. If infinite resistance Test for less than 2 ohms in the signal circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, replace the K33 HVAC Control Module. If 10 V or greater
  3. Ignition OFF, disconnect the harness connector at the K33 HVAC Control Module, ignition ON.
  4. Test for less than 1 V between the signal circuit terminal 2 and ground. If 1 V or greater Repair the short to voltage on the circuit. If less than 1 V
  5. Test or replace the B10B Ambient Light/Sunload Sensor.
  6. Verify DTC B1405 did not reset. If DTC B1405 reset Replace the K33 HVAC Control Module. If DTC B1405 did not reset
  7. All OK.

Repair Instructions

Perform the Diagnostic Repair Verification after completing the repair.

  1. «HVAC Component Replacement Reference»(/cadillac/srx/ii-2012-2016/remont/automatic-hvac-system/#hvac-system-automatic__hvac-component-replacement-reference)
  2. «Control Module References»(/cadillac/srx/ii-2012-2016/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for HVAC control module replacement, programming and setup
  1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/srx/ii-2012-2016/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/cadillac/srx/ii-2012-2016/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»(/cadillac/srx/ii-2012-2016/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
Upper Left Duct Air Temperature Sensor SignalB0173 02B0173 05B0173 05
Lower Left Duct Air Temperature Sensor SignalB0178 02B0178 05B0178 05
Upper Right Duct Air Temperature Sensor SignalB0509 02B0509 05B0509 05
Lower Right Duct Air Temperature Sensor SignalB0514 02B0514 05B0514 05
Rear Upper Duct Air Temperature Sensor SignalB0519 02B0519 05B0519 05
Rear Lower Duct Air Temperature Sensor SignalB3583 02B3583 05B3583 05
Air Conditioning Evaporator Temperature Sensor SignalB3933 02B3933 05B3933 05
Font Temperature Sensor Low ReferenceB0173 05, B0178 05, B0509 05, B0514 05, B3933 05B0173 05, B0178 05, B0509 05, B0514 05, B3933 05
Rear Temperature Sensor Low ReferenceB0519 05, B3583 05B0519 05, B3583 05

The air temperature sensors are a 2-wire negative temperature coefficient thermistor. The vehicle uses the following air temperature sensors

  1. Air temperature sensor - left upper
  2. Air temperature sensor - left lower
  3. Air temperature sensor - right upper
  4. Air temperature sensor - right lower
  5. Air temperature sensor - rear upper (With CJ4)
  6. Air temperature sensor - rear lower (With CJ4)
  7. A/C evaporator temperature sensor

This sensor operates using signal and low reference circuits. As the air temperature surrounding the sensor increases, the sensor resistance decreases. The sensor is capable of reading temperatures ranging from -40 to +115°C (-40 to +240°F), with a signal voltage between 0-5 V. If the HVAC control module detects a malfunctioning sensor the software uses a default air temperature value. The default action ensures that the HVAC system can adjust the inside air temperature near the desired temperature until the condition is corrected.

  1. Ignition ON.
  2. The HVAC control module is ON.

The HVAC control module detects the sensor signal out of range. The signal voltage is less than 0.1 V or greater than 4.9 V for more than 50 ms.

The system operates using a default value.

The sensor signal is within specified range between 0.1-4.9 V.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition ON.
  2. Verify the appropriate temperature sensor has a parameter displayed in HVAC scan tool information. If there is no scan tool parameter Refer to «Circuit/System Testing - Without Scan Tool Support»(/cadillac/srx/ii-2012-2016/remont/automatic-hvac-system/#hvac-system-automatic) . If there is a scan tool parameter
  3. Refer to «Circuit/System Testing - With Scan Tool Support»(/cadillac/srx/ii-2012-2016/remont/automatic-hvac-system/#hvac-system-automatic)

With Scan Tool Support

  1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the appropriate temperature sensor. It may take up to 10 min for all vehicle systems to power down.
  2. Test for less than 10 ohms between the low reference circuit terminal B and ground. If 10 ohms or greater Ignition OFF, disconnect the harness connector at the K33 HVAC Control Module. Test for less than 2 ohms in the low reference circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, replace the K33 HVAC Control Module. If less than 10 ohms
  3. Ignition ON.
  4. Verify the appropriate scan tool temperature sensor parameter is less than -37°C (-35°F) If greater than -37°C (-35°F) Ignition OFF, disconnect the harness connector at the K33 HVAC Control Module. Test for infinite resistance between the signal circuit terminal A and ground. If less than infinite resistance, repair the short to ground on the circuit. If infinite resistance, replace the K33 HVAC Control Module. If -37°C (-35°F) or less
  5. Install a 3 A fused jumper wire between the signal circuit terminal A and the low reference circuit terminal B.
  6. Verify the scan tool temperature sensor parameter is greater than 110°C (230°F). If less than 110°C (230°F) Ignition OFF, remove the jumper wire and disconnect the harness connector at the K33 HVAC Control Module, ignition ON. Test for less than 1 V between the signal circuit and ground. If 1 V or greater, repair the short to voltage on the circuit. If less than 1 V Ignition OFF Test for less than 2 ohms in the signal circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, replace the K33 HVAC Control Module. If 110°C (230°F) or greater
  7. Test or replace the temperature sensor.

Without Scan Tool Support

  1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the appropriate temperature sensor. It may take up to 10 min for all vehicle systems to power down.
  2. Test for less than 10 ohms between the low reference circuit terminal B and ground. If 10 ohms or greater Ignition OFF, disconnect the harness connector at the K33 HVAC Control Module. Test for less than 2 ohms in the low reference circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, replace the K33 HVAC Control Module. If less than 10 ohms
  3. Test for 4.8-5.2 V between the signal circuit terminal A and ground. If less than 4.8 V Ignition OFF, disconnect the harness connector at the K33 HVAC Control Module. Test for infinite resistance between the signal circuit and ground. If less than infinite resistance, repair the short to ground on the circuit. If infinite resistance Test for less than 2 ohms in the signal circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, replace the K33 HVAC Control Module. If greater than 5.2 V Ignition OFF, disconnect the harness connector at the K33 HVAC Control Module, ignition ON. Test for less than 1 V between the signal circuit and ground. If 1 V or greater, repair the short to voltage on the circuit. If less than 1 V, replace the K33 HVAC Control Module. If between 4.8-5.2 V
  4. Test or replace the temperature sensor.
  5. Operate the vehicle within the Conditions for Running the DTC. You may also operate the vehicle within the conditions that you observed from the Freeze Frame/Failure Records data.
  6. Verify the DTC does not set. If the DTC sets Replace the K33 HVAC Control Module. If the DTC does not set
  7. All OK

Perform the Diagnostic Repair Verification after completing the repair.

  1. «HVAC Component Replacement Reference»(/cadillac/srx/ii-2012-2016/remont/automatic-hvac-system/#hvac-system-automatic__hvac-component-replacement-reference)
  2. «Control Module References»(/cadillac/srx/ii-2012-2016/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for HVAC control module replacement, programming and setup
  1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/srx/ii-2012-2016/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/cadillac/srx/ii-2012-2016/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»(/cadillac/srx/ii-2012-2016/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

For symptom byte information, refer to Symptom Byte List .

CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
5 V ReferenceB1395 031B1395 07
Signal Terminal 2B048C 02B048C 05B048C 05
Signal Terminal 4B018A 02B018A 05B018A 05
Signal Terminal 5B048F 02B048F 05B048F 05
Low ReferenceB018A 05, B048C 05, B048F 05, B1395 03
1. Sensor Malfunction

The windshield temperature and inside moisture sensor includes the relative humidity sensor, windshield temperature sensor and humidity sensing element temperature sensor all in one assembly.

This sensor assembly provides information about

  1. Relative humidity level at the windshield inside the vehicle
  2. Temperature of the windshield inside the vehicle
  3. Temperature of the humidity sensor element

The relative humidity sensor measures the relative humidity of the compartment side of the windshield. It also detects the temperature of the windshield surface on the compartment side. Both values are used as control inputs for the HVAC control module application to calculate the fog risk on windshield compartment side and ability to reduce fuel consumption by decreasing A/C compressor usage to a minimum without causing any fog. The sensor will also enable partial recirculation mode in order to improve heat-up performance of the passenger compartment under cold ambient temperature conditions without the risk of mist build-up on the windshield. The humidity sensor element temperature sensor supplies the temperature of the humidity sensor element. It is only needed if the thermal contact between the humidity sensing element and the inside windshield surface is not sufficient.

  1. Ignition ON.
  2. The HVAC control module is ON.

B018A 02, B048C 02, or B048F 02

The HVAC control module detects the sensor signal out of range. The signal voltage is less than 0.1 V for more than 50 ms.

B018A 05, B048C 05, B048F 05 or B1395 07

The HVAC control module detects the sensor signal out of range. The signal voltage is greater than 4.9 V for more than 50 ms.

B1395 03

The HVAC control module detects the 5 V reference voltage out of range. The 5 V reference voltage is less than 4.5 V for more than 50 ms.

B1395 07

The HVAC control module detects the 5 V reference voltage out of range. The 5 V reference voltage is greater than 5.5 V for more than 50 ms.

  1. The system will use the last valid values as default.
  2. If no value is read at the time of fault, the HVAC control module uses 60% for humidity.

The condition for setting the DTC is no longer present.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the B160 Windshield Temperature and Inside Moisture Sensor. It may take up to 10 min for all vehicle systems to power down.
  2. Test for less than 10 ohms between the low reference circuit terminal 3 and ground. If 10 ohms or greater Ignition OFF, disconnect the harness connectors at the K33 HVAC Control Module. Test for less than 2 ohms in the low reference circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, replace the K33 HVAC Control Module. If less than 10 ohms
  3. Ignition ON.
  4. Test for 4.8-5.2 V between the 5 V reference circuit terminal 1 and ground. If less than 4.8 V Ignition OFF, disconnect the harness connectors at the K33 HVAC Control Module. Test for infinite resistance between the 5 V reference circuit and ground. If less than infinite resistance, repair the short to ground on the circuit. If infinite resistance Test for less than 2 ohms in the 5 V reference circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, replace the K33 HVAC Control Module. If greater than 5.2 V Ignition OFF, disconnect the harness connectors at the K33 HVAC Control Module, ignition ON. Test for less than 1 V between the 5 V reference circuit and ground. If 1 V or greater, repair the short to voltage on the circuit. If less than 1 V, replace the K33 HVAC Control Module. If between 4.8-5.2 V
  5. Verify the scan tool parameters listed below are less than -37°C (-35°F). Windshield Temperature Passenger Compartment Humidity Sensor Temperature If -37°C (-35°F) or greater Ignition OFF, disconnect the harness connectors at the K33 HVAC Control Module. Test for infinite resistance between the signal circuit terminals listed below and ground: Windshield temperature sensor signal terminal 4 Passenger compartment humidity sensor temperature signal terminal 5 If less than infinite resistance, repair the short to ground on the circuit. If infinite resistance, replace the K33 HVAC Control Module. If less than -37°C (-35°F)
  6. Install a 3 A fused jumper wire between the low reference circuit terminal 3 and each signal circuit terminal listed below: Windshield temperature sensor signal terminal 4 Passenger compartment humidity sensor temperature signal terminal 5
  7. Verify the appropriate scan tool parameter listed below is greater than 114°C (238°F). Windshield Temperature Passenger Compartment Humidity Sensor Temperature If 114°C (238°F) or less Ignition OFF, remove the jumper wire and disconnect the harness connectors at the K33 HVAC Control Module, ignition ON. Test for less than 1 V between the signal circuit terminals listed below and ground: Windshield temperature sensor signal terminal 4 Passenger compartment humidity sensor temperature signal terminal 5 If 1 V or greater, repair the short to voltage on the circuit. If less than 1 V Test for less than 2 ohms in the signal circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, replace the K33 HVAC Control Module. If greater than 114°C (238°F)
  8. Remove the jumper wire.
  9. Verify the scan tool Passenger Compartment Humidity parameter is greater than 95%. If 95% or less Ignition OFF, disconnect the harness connectors at the K33 HVAC Control Module, ignition ON. Test for infinite resistance between the signal circuit terminal 2 and ground. If less than infinite resistance, repair the short to ground on the circuit. If infinite resistance, replace the K33 HVAC Control Module. If greater than 95%
  10. Install a 3 A fused jumper wire between the passenger compartment humidity signal circuit terminal 2 and the low reference circuit terminal 3.
  11. Verify the scan tool Passenger Compartment Humidity Sensor parameter is less than 5%. If 5% or greater Ignition OFF, remove the jumper wire and disconnect the harness connectors at the K33 HVAC Control Module, ignition ON. Test for less than 1 V between the signal circuit terminal 2 and ground. If 1 V or greater, repair the short to voltage on the circuit. If less than 1 V Test for less than 2 ohms in the signal circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, replace the K33 HVAC Control Module. If less than 5%
  12. Test or replace the B160 Windshield Temperature and Inside Moisture Sensor.

Perform the Diagnostic Repair Verification after completing the repair.

  1. «HVAC Component Replacement Reference»(/cadillac/srx/ii-2012-2016/remont/automatic-hvac-system/#hvac-system-automatic__hvac-component-replacement-reference)
  2. «Control Module References»(/cadillac/srx/ii-2012-2016/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for HVAC control module replacement, programming and setup
  1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/srx/ii-2012-2016/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/cadillac/srx/ii-2012-2016/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»(/cadillac/srx/ii-2012-2016/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
B+B0193 06B0193 06
ControlB0193 06B0193 06B0193 01
GroundB0193 06

The blower motor control module is an interface between the HVAC control module and the blower motor. The blower motor control module has 4 circuits: a B+ input, a signal input from the HVAC module, a B+ output to the blower motor, and a low side pulse width modulation (PWM) output. The HVAC control module provides a low side (PWM) signal to the blower motor control module in order to request the blower motor speed. The blower motor control module grounds the blower motor using a low side PWM signal in order to vary the blower motor speed.

  1. Ignition ON.
  2. The HVAC control module is ON.

B0193 01

The voltage at the HVAC control module output to the blower motor control module is always high.

B0193 06

The voltage at the HVAC control module output to the blower motor control module is always low or fluctuating.

The blower motor is inoperative.

The condition for setting the DTC is no longer present.

Diagnostic Aids

Inspect the motor shaft for rust or other foreign material which may prohibit proper motor operation.

If the motor operates properly please reinstall it and check for Preliminary Information or Technical Service Bulletins.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition OFF and all vehicle systems OFF, disconnect the X1 harness connector at the K8 Blower Motor Control Module. It may take up to 2 min for all vehicle systems to power down.
  2. Test for less than 10 ohms between the ground circuit terminal 5 and ground. If 10 ohms or greater Ignition OFF. Test for less than 2 ohms in the ground circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, repair the open/high resistance in the ground connection. If less than 10 ohms
  3. Ignition ON.
  4. Verify a test lamp illuminates between the B+ circuit terminal 6 and ground. If the test lamp does not illuminate and the circuit fuse is good Ignition OFF, remove the test lamp. Test for less than 2 ohms in the B+ circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, verify the fuse is not open and there is voltage at the fuse. If the test lamp does not illuminate and the circuit fuse is open Ignition OFF, remove the test lamp. Test for infinite resistance between the B+ circuit terminal 6 and ground. If less than infinite resistance, repair the short to ground on the circuit. If infinite resistance Disconnect the X2 harness connector at the K8 Blower Motor Control Module and disconnect the harness connector at the M8 Blower Motor. Test for infinite resistance between the M8 Blower Motor B+ circuit terminal B and ground. If less than infinite resistance, repair the short to ground on the circuit. If infinite resistance, test or replace the M8 Blower Motor. If the test lamp illuminates
  5. Remove the test lamp.
  6. Verify the resistance between the control circuit terminal 3 and ground varies from 100K ohms to 150K ohms while changing blower speeds. If the resistance does not change from 100K ohms to 150K ohms Ignition OFF, disconnect the X2 harness connector at the K33 HVAC Control Module, ignition ON. Test for less than 1 V between the control circuit and ground. If 1 V or greater, repair the short to voltage on the circuit. If less than 1 V Test for infinite resistance between the control circuit and ground. If less than infinite resistance, repair the short to ground on the circuit. If infinite resistance. Test for less than 2 ohms in the control circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms replace the K33 HVAC Control Module. If the resistance does change from 100K ohms to 150K ohms
  7. Ignition OFF, connect the X1 harness connector at the K8 Blower Motor Control Module and disconnect the harness connector at the M8 Blower Motor, ignition ON and blower ON.
  8. Verify a test lamp illuminates between the B+ terminal B and ground. If the test lamp does not illuminate Ignition OFF, disconnect the X2 harness connector at the K8 Blower Motor Control Module. Test for less than 2 ohms in the B+ circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms replace the K8 Blower Motor Control Module. If the test lamp illuminates
  9. Connect a test lamp between the B+ circuit terminal B and control circuit terminal A, ignition ON.
  10. Verify the test lamp becomes progressively brighter as the blower speed is increased and progressively dimmer as the blower speed is decreased. If the test lamp does not illuminate Ignition OFF, remove the test lamp and disconnect the X2 harness connector at the K8 Blower Motor Control Module, ignition ON. Test for less than 1 V between the control circuit terminal 2 and ground. If 1 V or greater, repair the short to voltage on the circuit. If less than 1 V Test for less than 2 ohms in the control circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms replace the K8 Blower Motor Control Module. If the test lamp illuminates, but does not change in brightness Ignition OFF, remove the test lamp and disconnect the X2 harness connector at the K8 Blower Motor Control Module. Test for infinite resistance between the control circuit terminal 2 and ground. If less than infinite resistance, repair the short to ground on the circuit. If infinite resistance, replace the K8 Blower Motor Control Module. If the test lamp changes in brightness as the blower speed is changed
  11. Test or replace the M8 Blower Motor.

Perform the Diagnostic Repair Verification after completing the repair.

  1. «HVAC Component Replacement Reference»(/cadillac/srx/ii-2012-2016/remont/automatic-hvac-system/#hvac-system-automatic__hvac-component-replacement-reference)
  2. «Control Module References»(/cadillac/srx/ii-2012-2016/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for HVAC control module replacement, programming and setup
  1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/srx/ii-2012-2016/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/cadillac/srx/ii-2012-2016/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»(/cadillac/srx/ii-2012-2016/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
B+B0208 06B0208 06
ControlB0208 06B0208 06B0208 01
GroundB0208 06

The auxiliary blower motor control module is an interface between the HVAC control module and the auxiliary blower motor. The auxiliary blower motor control module has 4 circuits: a B+ input, a signal input from the HVAC module, a B+ output to the auxiliary blower motor, and a low side pulse width modulation (PWM) output. The HVAC control module provides a low side (PWM) signal to the auxiliary blower motor control module in order to request the auxiliary blower motor speed. The auxiliary blower motor control module grounds the blower motor using a low side PWM signal in order to vary the auxiliary blower motor speed.

  1. Ignition ON.
  2. The HVAC control module is ON.

B0208 01

The voltage at the HVAC control module output to the auxiliary blower motor control module is always high.

B0208 06

The voltage at the HVAC control module output to the auxiliary blower motor control module is always low or fluctuating.

The auxiliary blower motor is inoperative.

The condition for setting the DTC is no longer present.

Inspect the motor shaft for rust or other foreign material which may prohibit proper motor operation.

If the motor operates properly please reinstall it and check for Preliminary Information or Technical Service Bulletins.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition OFF and all vehicle systems OFF, disconnect the X1 harness connector at the K8A Blower Motor Control Module - Auxiliary. It may take up to 2 min for all vehicle systems to power down.
  2. Test for less than 10 ohms between the ground circuit terminal 4 and ground. If 10 ohms or greater Ignition OFF. Test for less than 2 ohms in the ground circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, repair the open/high resistance in the ground connection. If less than 10 ohms
  3. Ignition ON.
  4. Verify a test lamp illuminates between the B+ circuit terminal 2 and ground. If the test lamp does not illuminate and the circuit fuse is good Ignition OFF, remove the test lamp. Test for less than 2 ohms in the B+ circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, verify the fuse is not open and there is voltage at the fuse. If the test lamp does not illuminate and the circuit fuse is open Ignition OFF, remove the test lamp. Test for infinite resistance between the B+ circuit and ground. If less than infinite resistance, repair the short to ground on the circuit. If infinite resistance Disconnect the X2 harness connector at the K8A Blower Motor Control Module - Auxiliary and disconnect the harness connector at the M8B Blower Motor - Auxiliary. Test for infinite resistance between the M8B Blower Motor - Auxiliary B+ circuit terminal B and ground. If less than infinite resistance, repair the short to ground on the circuit. If infinite resistance, test or replace the M8B Blower Motor - Auxiliary. If the test lamp illuminates
  5. Remove the test lamp.
  6. Verify the resistance between the control circuit terminal 1 and ground varies from 100 ohms to 90K ohms while changing blower speeds. If the resistance does not change from 100 ohms to 90K ohms Ignition OFF, disconnect the X2 harness connector at the K33 HVAC Control Module, ignition ON. Test for less than 1 V between the control circuit and ground. If 1 V or greater, repair the short to voltage on the circuit. If less than 1 V Test for infinite resistance between the control circuit and ground. If less than infinite resistance, repair the short to ground on the circuit. If infinite resistance. Test for less than 2 ohms in the control circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms replace the K33 HVAC Control Module. If the resistance does change from 100 ohms to 90K ohms
  7. Ignition OFF, connect the X1 harness connector at the K8A Blower Motor Control Module - Auxiliary and disconnect the harness connector at the M8B Blower Motor - Auxiliary, ignition ON and blower ON.
  8. Verify a test lamp illuminates between the B+ terminal B and ground. If the test lamp does not illuminate Ignition OFF, disconnect the X2 harness connector at the K8A Blower Motor Control Module - Auxiliary. Test for less than 2 ohms in the B+ circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms replace the K8A Blower Motor Control Module - Auxiliary. If the test lamp illuminates
  9. Connect a test lamp between the B+ circuit terminal B and control circuit terminal A, ignition ON.
  10. Verify the test lamp becomes progressively brighter as the blower speed is increased and progressively dimmer as the blower speed is decreased. If the test lamp does not illuminate Ignition OFF, remove the test lamp and disconnect the X2 harness connector at the K8A Blower Motor Control Module - Auxiliary, ignition ON. Test for less than 1 V between the control circuit terminal A and ground. If 1 V or greater, repair the short to voltage on the circuit. If less than 1 V Test for less than 2 ohms in the control circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms replace the K8A Blower Motor Control Module - Auxiliary. If the test lamp illuminates, but does not change in brightness Ignition OFF, remove the test lamp and disconnect the X2 harness connector at the K8 Blower Motor Control Module. Test for infinite resistance between the control circuit terminal A and ground. If less than infinite resistance, repair the short to ground on the circuit. If infinite resistance, replace the K8A Blower Motor Control Module - Auxiliary. If the test lamp changes in brightness as the blower speed is changed
  11. Test or replace the M8B Blower Motor - Auxiliary.

Perform the Diagnostic Repair Verification after completing the repair.

  1. «HVAC Component Replacement Reference»(/cadillac/srx/ii-2012-2016/remont/automatic-hvac-system/#hvac-system-automatic__hvac-component-replacement-reference)
  2. «Control Module References»(/cadillac/srx/ii-2012-2016/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for HVAC control module replacement, programming and setup
  1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/srx/ii-2012-2016/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/cadillac/srx/ii-2012-2016/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»(/cadillac/srx/ii-2012-2016/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
Stepper Motors 12 V ReferenceB022A 06, B023A 02, B0223 06, B0233 06, B0408 06, B0418 06, B0428 06B022A 06, B0223 06, B0233 06, B0408 06, B0418 06, B0428 06
Recirculation Actuator Control 1B0223 06B0223 06B0223 011
Recirculation Actuator Control 2B0223 06B0223 06B0223 011
Recirculation Actuator Control 3B0223 06B0223 06B0223 011
Recirculation Actuator Control 4B0223 06B0223 06B0223 011
Air Temperature Actuator Control 1B0408 06B0408 06B0408 011
Air Temperature Actuator Control 2B0408 06B0408 06B0408 011
Air Temperature Actuator Control 3B0408 06B0408 06B0408 011
Air Temperature Actuator Control 4B0408 06B0408 06B0408 011
Passenger Air Temperature Actuator Control 1B0418 06B0418 06B0418 011
Passenger Air Temperature Actuator Control 2B0418 06B0418 06B0418 011
Passenger Air Temperature Actuator Control 3B0418 06B0418 06B0418 011
Passenger Air Temperature Actuator Control 4B0418 06B0418 06B0418 011
Mode Actuator Control 1B0233 06B0233 06B0233 011
Mode Actuator Control 2B0233 06B0233 06B0233 011
Mode Actuator Control 3B0233 06B0233 06B0233 011
Mode Actuator Control 4B0233 06B0233 06B0233 011
Rear Temperature Actuator Control 1B0428 06B0428 06B0428 011
Rear Temperature Actuator Control 2B0428 06B0428 06B0428 011
Rear Temperature Actuator Control 3B0428 06B0428 06B0428 011
Rear Temperature Actuator Control 4B0428 06B0428 06B0428 011
Rear Air Flow Actuator Control 1B3531 06B3531 06B3531 011
Rear Air Flow Actuator Control 2B3531 06B3531 06B3531 011
Rear Air Flow Actuator Control 3B3531 06B3531 06B3531 011
Rear Air Flow Actuator Control 4B3531 06B3531 06B3531 011
1. HVAC Malfunction

Stepper motors are used for temperature regulation, air distribution control and recirculation door control.

With the switches and dials on the HVAC controls, air temperature door position, mode door position and recirculation door position can be selected. The selected values are passed to the HVAC control module via serial data. The HVAC control module supplies a 12 V reference voltage to the stepper motors and energizes the 4 stepper motor coils with a pulsed ground signal. The stepper motors move the appropriate doors into the calculated positions, in order to reach the desired positions.

  1. Ignition ON.
  2. The HVAC control module is ON.

B023A 02

The stepper motor supply output is shorted to ground.

B0223 01, B022A 01, B0233 01, B0408 01, B0418 01, B0428 01 or B3531 01

At least one of the stepper motor control circuits is shorted to voltage when motor starts moving. Faults are not detected when motor is already running or target position is already reached.

B0223 06, B022A 06, B0233 06, B0408 06, B0418 06, B0428 06 or B3531 06

At least one of the stepper motor control circuits is shorted to ground or open when motor starts moving. Faults are not detected when motor is already running or target position is already reached.

B023A 02

  1. The affected output will be switched off for hardware protection.
  2. All stepper motors are deactivated.

B0223, B022A, B0233, B0408, B0418, B0428 or B3531

  1. The affected output will be switched off for hardware protection.
  2. The affected stepper motor is deactivated.

The condition for setting the DTC is no longer present.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Perform the «Actuator Recalibration»(/cadillac/srx/ii-2012-2016/remont/automatic-hvac-system/#hvac-system-automatic) procedure.
  2. Verify the concern or DTC has been corrected. If the concern or DTC has not been corrected Verify DTC B023A is not set. If DTC B023A is set, refer to «Circuit/System Testing - DTC B023A»(/cadillac/srx/ii-2012-2016/remont/automatic-hvac-system/#hvac-system-automatic) . If DTC B023A is not set, refer to «Circuit/System Testing - DTC B0223, B022A, B0233, B0408, B0418, B0428 or B3531»(/cadillac/srx/ii-2012-2016/remont/automatic-hvac-system/#hvac-system-automatic) . If the concern or DTC has been corrected
  3. All OK.

DTC B023A

  1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the components listed below. It may take up to 2 min for all vehicle systems to power down. M4 Air Inlet Door Actuator M37 Mode Door Actuator M46 Air Recirculation Door Actuator M6L Air Temperature Door Actuator - Left M6R Air Temperature Door Actuator - Right M37B Mode Door Actuator - Auxiliary M6B Air Temperature Door Actuator - Auxiliary
  2. Disconnect the X3 and X4 harness connectors at the K33 HVAC Control Module.
  3. Test for infinite resistance between the K33 HVAC Control Module 12 V reference circuit terminal 15 X3 and ground. If less than infinite resistance Repair the short to ground on the circuit. If infinite resistance
  4. Ignition ON.
  5. Test for less than 1 V between the K33 HVAC Control Module 12 V reference circuit terminal 15 X3 and ground. If 1 V or greater Repair the short to voltage on the circuit. If less than 1 V
  6. Connect the X3 and X4 harness connectors at the K33 HVAC Control Module, ignition ON.
  7. Clear all DTCs.
  8. Verify DTC B023A is not set. If the DTC is set. Replace the K33 HVAC Control Module. If the DTC is not set.
  9. Verify DTC B023A does not set after connecting each of the components listed below one at a time and operating them through their full range. M4 Air Inlet Door Actuator M37 Mode Door Actuator M46 Air Recirculation Door Actuator M6L Air Temperature Door Actuator - Left M6R Air Temperature Door Actuator - Right M37B Mode Door Actuator - Auxiliary M6B Air Temperature Door Actuator - Auxiliary If the DTC sets Replace the component that was connected immediately before the DTC set. If the DTC does not set
  10. All OK.

DTC B0223, B022A, B0233, B0408, B0418, B0428 or B3531

  1. Ignition OFF, disconnect the harness connector at the appropriate door actuator, ignition ON.
  2. Verify a test lamp flashes when connected between the 12 V reference circuit terminal 2 and ground. If the test lamp does not flash Ignition OFF, remove the test lamp and disconnect the harness connector at the K33 HVAC Control Module. Test for less than 2 ohms in the 12 V control circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, replace the K33 HVAC Control Module. If the test lamp flashes
  3. Connect a test lamp between each control circuit listed below and B+. Control Circuit - terminal 1 Control Circuit - terminal 3 Control Circuit - terminal 4 Control Circuit - terminal 6
  4. Command the appropriate door actuator in both directions.
  5. Verify the test lamp turns ON and then OFF during at least one of the directional commands. If the test lamp is always ON Ignition OFF, remove the test lamp and disconnect the harness connector at the K33 HVAC Control Module. Test for infinite resistance between the control circuit and ground. If less than infinite resistance, repair the short to ground on the circuit. If infinite resistance, replace the K33 HVAC Control Module. If the test lamp is always OFF Ignition OFF, remove the test lamp and disconnect the harness connector at the K33 HVAC Control Module, ignition ON. Test for less than 1 V between the control circuit and ground. If 1 V or greater, repair the short to voltage on the circuit. If less than 1 V Ignition OFF Test for less than 2 ohms in the control circuit end to end. If 2 ohms or greater, repair the open/high resistance is the circuit. If less than 2 ohms, replace the K33 HVAC Control Module. If the test lamp turns ON and then OFF
  6. Test or replace the door actuator.

Perform the Diagnostic Repair Verification after completing the repair.

  1. «HVAC Component Replacement Reference»(/cadillac/srx/ii-2012-2016/remont/automatic-hvac-system/#hvac-system-automatic__hvac-component-replacement-reference)
  2. «Control Module References»(/cadillac/srx/ii-2012-2016/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for HVAC control module replacement, programming and setup
  1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/srx/ii-2012-2016/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/cadillac/srx/ii-2012-2016/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»(/cadillac/srx/ii-2012-2016/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The HVAC control module and the HVAC control module - auxiliary communicates with each other via serial data. This DTC indicates a fault in the HVAC control module - auxiliary. No external circuits are involved. The HVAC system may continue to respond normally to faceplate functions when this DTC is set.

  1. Ignition is ON or in the ACC position.
  2. The system voltage is at least 9.5 V and no more than 15.5 V.
  3. All the above conditions are present for greater than 10 seconds.

The HVAC control module receives an improper status response indicating an internal ECU fault in the HVAC control module - auxiliary.

No action is taken.

  1. A current DTC clears when the HVAC control module receives a proper status response message back from the HVAC control module - auxiliary assembly.
  2. A history DTC clears after 50 malfunction-free ignition cycles.
  1. This DTC may be stored as a history DTC without affecting the operation of the HVAC control module - auxiliary.
  2. If stored only as a history DTC and not retrieved as a current DTC, do not replace the HVAC control module - auxiliary.
  3. If this DTC is retrieved as both a current and history DTC, replace the HVAC control module - auxiliary.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition ON.
  2. Verify DTC B1020 39 is not set. If the DTC is set Replace the K33A HVAC Control Module - Auxiliary. If the DTC is not set
  3. All OK

Perform the Diagnostic Repair Verification after completing the repair.

Control Module References for HVAC control module - auxiliary replacement, programming and setup

  1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/srx/ii-2012-2016/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/cadillac/srx/ii-2012-2016/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»(/cadillac/srx/ii-2012-2016/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
IgnitionB3843 05B3843 05
SignalB3843 02B3843 05B3843 05B3843 08
GroundB3843 05

The HVAC control module uses an air quality sensor to detect hydrocarbons. This sensor operates using an ignition voltage circuit, a ground circuit and a signal circuit.

This information is sent to the HVAC control module using a pulse width modulated (PWM) signal. It is used only when the automatic HVAC mode is requested by the customer.

When the HVAC module detects the concentration of pollutants exceeds a preset value, recirculation mode is commanded to keep the passenger compartment free of pollutants.

  1. Ignition ON
  2. The HVAC control module is ON.

B3843 02

No PWM is detected and the signal is low.

B3843 05

No PWM is detected and the signal is high.

B3843 08

The sensor sends a 5% PWM signal indicating an internal sensor short circuit or open circuit.

The automatic recirculation mode is disabled.

The condition for setting the DTC is no longer present.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the B108 Air Quality Sensor. It may take up to 2 min for all vehicle systems to power down.
  2. Test for less than 10 ohms between the ground circuit terminal 2 and ground. If 10 ohms or greater Ignition OFF. Test for less than 2 ohms in the ground circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, repair the open/high resistance in the ground connection. If less than 10 ohms
  3. Ignition ON.
  4. Verify a test lamp illuminates between the ignition circuit terminal 1 and ground. If the test lamp does not illuminate and the circuit fuse is good Ignition OFF, remove the test lamp. Test for less than 2 ohms in the ignition circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, verify the fuse is OK and there is voltage at the fuse. If the test lamp does not illuminate and the circuit fuse is open Ignition OFF, remove the test lamp. Test for infinite resistance between the ignition circuit and ground. If less than infinite resistance, repair the short to ground on the circuit. If infinite resistance, replace the B108 Air Quality Sensor. If the test lamp illuminates
  5. Install a test lamp between the signal circuit terminal 3 and the ignition circuit terminal 1. NOTE: This connection may need to be in place for nearly 60 seconds before there is a change in the parameter.
  6. Verify the scan tool Air Quality Sensor parameter is greater than 95%. If the parameter is 95% or less Ignition OFF, remove the test lamp and disconnect the harness connector at the K33 HVAC Control Module. Test for infinite resistance between the signal circuit and ground. If less than infinite resistance, repair the short to ground on the circuit. If infinite resistance Test for less than 2 ohms in the signal circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, replace the K33 HVAC Control Module. If the parameter is greater than 95%
  7. Remove the test lamp and Install a 3 A fused jumper wire between the signal circuit terminal 3 and the ground circuit terminal 2. NOTE: This connection may need to be in place for nearly 60 seconds before there is a change in the parameter.
  8. Verify the scan tool Air Quality Sensor parameter is less than 5%. If the parameter is 5% or greater Ignition OFF, remove the jumper wire and disconnect the harness connector at the K33 HVAC Control Module, ignition ON. Test for less than 1 V between the signal circuit and ground. If 1 V or greater, repair the short to voltage on the circuit. If less than 1 V Ignition OFF Test for less than 2 ohms in the signal circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, replace the K33 HVAC Control Module. If the parameter is less than 5%
  9. Replace the B108 Air Quality Sensor.

Perform the Diagnostic Repair Verification after completing the repair.

  1. «HVAC Component Replacement Reference»(/cadillac/srx/ii-2012-2016/remont/automatic-hvac-system/#hvac-system-automatic__hvac-component-replacement-reference)
  2. «Control Module References»(/cadillac/srx/ii-2012-2016/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for HVAC control module replacement, programming and setup
  1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/srx/ii-2012-2016/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/cadillac/srx/ii-2012-2016/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»(/cadillac/srx/ii-2012-2016/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

DTC Descriptor

For symptom byte information, refer to Symptom Byte List .

CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
B+1B393B 04
ControlB393B 04B393B 04B393B 0B
1. Solenoid Valve Malfunction

This A/C system uses a conventional clutch to engage and mechanically turn the compressor and a variable displacement solenoid valve to alter the amount of displacement created by the turning of the compressor. The HVAC control module provides both battery voltage and a pulse width modulated ground to the variable displacement solenoid valve. When the A/C switch is pressed, the HVAC control module grounds the variable displacement solenoid using a low side (PWM) signal in order to command the amount of compressor displacement. The performance of the A/C compressor is based on adjusted interior temperature and engine load.

  1. Ignition ON.
  2. The HVAC control module is ON.

B393B 04

A PWM greater than 10% is sent but no current is read back.

B393B 0B

Measured current is above threshold of 815 mA.

B393B 04

The A/C compressor is disabled.

B393B 0B

  1. The A/C compressor is disabled.
  2. Output will be switched off for hardware protection.

The condition for setting the DTC is no longer present.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#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 Q46 A/C Compressor Solenoid Valve, ignition ON.
  2. Verify a test lamp illuminates between the B+ circuit terminal 2 and ground. If the test lamp does not illuminate Ignition OFF, remove the test lamp and disconnect the harness connectors at the K33 HVAC Control Module. Test for infinite resistance between the Q46 A/C Compressor Solenoid Valve B+ circuit terminal 2 and ground. If less than infinite resistance, repair the short to ground on the circuit. If infinite resistance. Test for less than 2 ohms in the B+ circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, replace the K33 HVAC Control Module. If the test lamp illuminates
  3. Ignition OFF, connect a test lamp between the control circuit terminal 1 and the B+ circuit terminal 2, ignition ON.
  4. Verify the test lamp turns ON and OFF when commanding the Q46 A/C Compressor Refrigerant Solenoid Valve On and Off with a scan tool. If the test lamp is always OFF Ignition OFF, remove the test lamp and disconnect the harness connectors at the K33 HVAC Control Module, ignition ON. Test for less than 1 V between the Q46 A/C Compressor Refrigerant Solenoid Valve control circuit terminal 1 and ground. If 1 V or greater, repair the short to voltage on the circuit. If less than 1 V Ignition OFF. Test for less than 2 ohms in the control circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, replace the K33 HVAC Control Module. If the test lamp is always ON Ignition OFF, remove the test lamp and disconnect the harness connectors at the K33 HVAC Control Module. Test for infinite resistance between the Q46 A/C Compressor Refrigerant Solenoid Valve control circuit terminal 1 and ground. If less than infinite resistance, repair the short to ground on the circuit. If infinite resistance, replace the K33 HVAC Control Module. If the test lamp turns ON and OFF
  5. Test or replace the G1 A/C Compressor.

Component Testing

A/C Compressor Solenoid Valve Test

  1. Ignition OFF, disconnect the harness connector at the Q46 A/C Compressor Solenoid Valve.
  2. Test for 7-15 ohms between B+ terminal 2 and control terminal 1. If less than 7 ohms or greater than 15 ohms Replace the G1 A/C Compressor. If between 7-15 ohms
  3. Test for infinite resistance between each terminal and the Q46 A/C Compressor Solenoid Valve housing/case. If less than infinite resistance Replace the G1 A/C Compressor. If infinite resistance
  4. All OK.

Perform the Diagnostic Repair Verification after completing the repair.

  1. «HVAC Component Replacement Reference»(/cadillac/srx/ii-2012-2016/remont/automatic-hvac-system/#hvac-system-automatic__hvac-component-replacement-reference)
  2. «Control Module References»(/cadillac/srx/ii-2012-2016/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for HVAC control module replacement, programming and setup
  1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/srx/ii-2012-2016/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/cadillac/srx/ii-2012-2016/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»(/cadillac/srx/ii-2012-2016/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of the diagnostic category.
CircuitShort to GroundOpen/High ResistanceShort to VoltageSignal Performance
5 V ReferenceP0532, P0641P0532P0533
SignalP0532P0532P0533
Low ReferenceP0533

The engine control module (ECM) monitors the high side refrigerant pressure through the A/C refrigerant pressure sensor. The ECM supplies a 5 V reference and a low reference to the sensor. Changes in the A/C refrigerant pressure cause the sensor signal to the ECM to vary. When the pressure is high, the signal voltage is high. When the pressure is low, the signal voltage is low. The ECM may use this information to turn the cooling fans on as well as to monitor clutch engagement. The HVAC module will receive the A/C refrigerant pressure information from the ECM via serial data.

  1. Engine is running.
  2. Any of the conditions for setting the DTC are met for 15 s.
  3. Battery voltage is between 11-18 V.

P0532

The ECM detects that the A/C pressure is less than 1 psi (0.25 V).

P0533

The ECM detects that the A/C pressure is more than 428 psi (4.92 V).

  1. The A/C compressor is disabled.
  2. The ECM will illuminate the malfunction indicator lamp (MIL).

The condition for setting the DTC is no longer present.

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

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

DTC Type Reference

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition ON
  2. Verify the scan tool engine control module A/C High Side Pressure Sensor parameter is between 6.8 kPa (1 psi) and 2950 kPa (428 psi). If not between 6.8 kPa (1 psi) and 2950 kPa (428 psi) Refer to Circuit/System Testing (below). If between 6.8 kPa (1 psi) and 2950 kPa (428 psi)
  3. All OK
  1. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the B1 A/C Refrigerant Pressure Sensor. It may take up to 2 min for all vehicle systems to power down.
  2. Test for less than 10 ohms between the low reference circuit terminal 1 and ground. If 10 ohms or greater Ignition OFF, disconnect the harness connector at the K20 Engine Control Module. Test for less than 2 ohms in the low reference circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, replace the K20 Engine Control Module. If less than 10 ohms
  3. Ignition ON.
  4. Test for 4.8-5.2 V between the 5 V reference circuit terminal 2 and ground. If less than 4.8 V Ignition OFF, disconnect the harness connector at the K20 Engine Control Module. Test for infinite resistance between the 5 V reference circuit and ground. If less than infinite resistance, repair the short to ground on the circuit. If infinite resistance Test for less than 2 ohms in the 5 V reference circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, replace the K20 Engine Control Module. If greater than 5.2 V Ignition OFF, disconnect the harness connector at the K20 Engine Control Module, ignition ON. Test for less than 1 V between the 5 V reference circuit and ground. If 1 V or greater, repair the short to voltage on the circuit. If less than 1 V, replace the K20 Engine Control Module. If between 4.8-5.2 V
  5. Verify the scan tool A/C High Side Pressure Sensor parameter is less than .25 V. If .25 V or greater Ignition OFF, disconnect the harness connector at the K20 Engine Control Module, ignition ON. Test for less than 1 V between the signal circuit terminal 3 and ground. If 1 V or greater, repair the short to voltage on the circuit. If less than 1 V, replace the K20 Engine Control Module. If less than .25 V
  6. Install a 3 A fused jumper wire between the signal circuit terminal 3 and the 5 V reference circuit terminal 2.
  7. Verify the scan tool A/C High Side Pressure Sensor parameter is greater than 4.8 V. If 4.8 V or less Ignition OFF, remove the jumper wire, disconnect the harness connector at the K20 Engine Control Module. Test for infinite resistance between the signal circuit terminal 3 and ground. If less than infinite resistance, repair the short to ground on the circuit. If infinite resistance Test for less than 2 ohms in the signal circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, replace the K20 Engine Control Module. If greater than 4.8 V
  8. Test or replace the B1 A/C Refrigerant Pressure Sensor.

Perform the Diagnostic Repair Verification after completing the repair.

  1. «HVAC Component Replacement Reference»(/cadillac/srx/ii-2012-2016/remont/automatic-hvac-system/#hvac-system-automatic__hvac-component-replacement-reference)
  2. «Control Module References»(/cadillac/srx/ii-2012-2016/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for engine control module replacement, programming and setup
  1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/srx/ii-2012-2016/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/cadillac/srx/ii-2012-2016/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»(/cadillac/srx/ii-2012-2016/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
Relay Coil IgnitionP0645P0645
Relay Switch B+11
Relay Coil ControlP0646P0645P0647
Relay Switch Control111
Ground1
1. A/C Compressor Malfunction

When the A/C switch is pressed, the HVAC control module sends an A/C request message to the engine control module (ECM) via serial data. The ECM then grounds the A/C compressor clutch relay coil control circuit, closing the relay contacts. The closed relay contacts provide voltage to the compressor clutch causing it to engage.

  1. Engine is running.
  2. The HVAC control module is ON.
  3. The A/C switch is active.

P0645 or P0646

The ECM detects a short to ground or an open at the A/C compressor clutch relay control circuit.

P0647

The ECM detects a short to voltage at the A/C compressor clutch relay control circuit.

P0645 or P0646

The A/C compressor is inoperative or always active. The A/C compressor solenoid is commanded to 0% displacement. This causes warm air from the ducts, even with unwanted clutch engagement.

P0647

The A/C compressor is inoperative.

The condition for setting the DTC is no longer present.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

DTC Type Reference

Scan Tool Reference

Control Module References for scan tool information

  1. Ignition OFF, disconnect the KR29 A/C Compressor Clutch Relay, ignition ON.
  2. Verify a test lamp illuminates between the B+ circuit terminal 30 and ground. If the test lamp does not illuminate and the circuit fuse is good Ignition OFF, remove the test lamp. Test for less than 2 ohms in the B+ circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, verify the fuse is not open and there is voltage at the fuse. If the test lamp does not illuminate and the circuit fuse is open Ignition OFF, remove the test lamp. Test for infinite resistance between the B+ circuit and ground. If less than infinite resistance, repair the short to ground on the circuit. If infinite resistance Disconnect the harness connector at the Q2 A/C Compressor Clutch. Test for infinite resistance between the control circuit terminal 87 and ground. If less than infinite resistance, repair the short to ground on the circuit. If infinite resistance, test or replace the Q2 A/C Compressor Clutch. If the test lamp illuminates
  3. Ignition ON.
  4. Verify a test lamp illuminates between the ignition circuit terminal 85 and ground. If the test lamp does not illuminate Refer to «Power Mode Mismatch»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures) . If the test lamp illuminates
  5. Connect a test lamp between the ignition circuit terminal 85 and the control circuit terminal 86.
  6. Verify the test lamp turns ON and OFF when commanding the ECM A/C Compressor Clutch Relay On and Off with a scan tool. If the test lamp is always OFF Ignition OFF, remove the test lamp and disconnect the harness connector at the K20 Engine Control Module, ignition ON. Test for less than 1 V between the control circuit and ground. If 1 V or greater, repair the short to voltage on the circuit. If less than 1 V Ignition OFF. Test for less than 2 ohms in the control circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, replace the K20 Engine Control Module. If the test lamp is always ON Ignition OFF, remove the test lamp and disconnect the harness connector at the K20 Engine Control Module. Test for infinite resistance between the control circuit and ground. If less than infinite resistance, repair the short to ground on the circuit. If infinite resistance, replace the K20 Engine Control Module. If the test lamp turns ON and OFF
  7. Verify a test lamp does not illuminate between the control circuit terminal 87 and ground. If the test lamp illuminates Repair the short to voltage on the circuit. If the test lamp does not illuminate
  8. Ignition OFF and all vehicle systems OFF, disconnect the harness connector at the Q2 A/C Compressor Clutch. It may take up to 2 min for all vehicle systems to power down.
  9. Test for less than 10 ohms between the ground circuit terminal 1 and ground. If 10 ohms or greater Ignition OFF. Test for less than 2 ohms in the ground circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, repair the open/high resistance in the ground connection. If less than 10 ohms
  10. Connect the harness connector at the Q2 A/C Compressor Clutch.
  11. Ignition ON, connect a 10 A fused jumper wire between the B+ circuit terminal 30 and the control circuit terminal 87.
  12. Verify the Q2 A/C Compressor Clutch is engaged. If the Q2 A/C Compressor Clutch does not engage Ignition OFF, disconnect the harness connector at the Q2 A/C Compressor Clutch. Test for less than 2 ohms in the control circuit end to end. If 2 ohms or greater, repair the open/high resistance in the circuit. If less than 2 ohms, test or replace the Q2 A/C Compressor Clutch. If the Q2 A/C Compressor Clutch is engaged
  13. Test or replace the KR29 A/C Compressor Clutch Relay.
  1. Ignition OFF, disconnect the KR29 A/C Compressor Clutch Relay.
  2. Test for 60-180 ohms between terminals 85 and 86. If not between 60-180 ohms Replace the KR29 A/C Compressor Clutch Relay. If between 60-180 ohms
  3. Test for infinite resistance between the terminals listed below: 30 and 86 30 and 87 30 and 85 85 and 87 If less than infinite resistance Replace the KR29 A/C Compressor Clutch Relay. If infinite resistance
  4. Install a 15 A fused jumper wire between terminal 86 and 12 V. Install a jumper wire between terminal 85 and ground.
  5. Test for less than 2 ohms between terminals 30 and 87. If 2 ohms or greater Replace the KR29 A/C Compressor Clutch Relay. If less than 2 ohms
  6. All OK.

Perform the Diagnostic Repair Verification after completing the repair.

  1. «HVAC Component Replacement Reference»(/cadillac/srx/ii-2012-2016/remont/automatic-hvac-system/#hvac-system-automatic__hvac-component-replacement-reference)
  2. «Control Module References»(/cadillac/srx/ii-2012-2016/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for engine control module replacement, programming and setup

Symptoms - HVAC Systems - Automatic

Note. Perform the Diagnostic System Check - Vehicle before using the Symptom Tables in order to verify that all of the following conditions are true: There are no DTCs set. The control modules can communicate via the serial data link. Review the system operation in order to familiarize yourself with the system functions. Refer to Steering Wheel Controls Description and Operation .

Visual/Physical Inspection

  1. Inspect for aftermarket devices which may affect the operation of the Steering Wheel Controls System. Refer to «Checking Aftermarket Accessories»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__checking-aftermarket-accessories) .
  2. Inspect for easily accessible or visible system components for obvious damage or conditions which may cause the symptom.

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 HVAC System Malfunction in order to diagnose the symptom.

  1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/srx/ii-2012-2016/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/cadillac/srx/ii-2012-2016/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»(/cadillac/srx/ii-2012-2016/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

Check the following mechanical fault sources

  1. Air distribution box
  2. Air distribution hoses/air distribution ducts

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Special Tools

J43600 ACR Air Conditioning Service Center

Note. Check for bulletins before proceeding.

  1. Ignition ON.
  2. Verify every applicable scan tool Switch parameter changes when pressing the appropriate switch on the A20 Radio/HVAC Controls. If any parameter does not change Replace the A20 Radio/HVAC Controls. If all parameters change
  3. Verify every applicable scan tool Switch parameter changes when pressing the appropriate switch on the K33A HVAC Control Module - Auxiliary. If any parameter does not change Replace the K33A HVAC Control Module - Auxiliary. If all parameters change
  4. Verify the front blower motor operates properly with the blower motor switch in each speed position. If the front blower motor does not operate in each speed position Refer to «DTC B0193»(/cadillac/srx/ii-2012-2016/remont/automatic-hvac-system/#hvac-system-automatic) . If the front blower motor operates properly in each speed position
  5. Verify the rear blower motor operates properly with the blower motor switch in each speed position. If the rear blower motor does not operate in each speed position Refer to «DTC B0208»(/cadillac/srx/ii-2012-2016/remont/automatic-hvac-system/#hvac-system-automatic) . If the rear blower motor operates properly in each speed position
  6. Verify the HVAC doors listed below move when pressing the appropriate switch. Driver Temperature Passenger Temperature Mode Recirculation Auxiliary Mode Auxiliary Temperature If any HVAC door does not move Refer to «DTC B0223, B022A, B0233, B023A, B0408, B0418, B0428, or B3531»(/cadillac/srx/ii-2012-2016/remont/automatic-hvac-system/#hvac-system-automatic) . If all HVAC doors move
  7. Install the J43600 ACR Air Conditioning Service Center.
  8. Verify the high side pressure reading on the Air Conditioning Service Center is within 10% of the scan tool ECM A/C High Side Pressure Sensor parameter. If the reading is not within 10% Refer to «DTC P0532 or P0533»(/cadillac/srx/ii-2012-2016/remont/automatic-hvac-system/#hvac-system-automatic) . If the reading is within 10%
  9. Verify the A/C High Side Pressure Sensor parameter is between 269-2929 kPa (39-425 PSI). If the reading is not between 269-2929 kPa (39-425 PSI) Refer to «Air Conditioning (A/C) System Performance Test (LF1 or LFX)»(/cadillac/srx/ii-2012-2016/remont/automatic-hvac-system/#heating-ventilation-and-air-conditioning) . If the reading is between 269-2929 kPa (39-425 PSI)
  10. Verify the scan tool parameters listed below are within 10% of ambient temperature. Lower Left Duct Air Temperature Sensor Upper Left Duct Air Temperature Sensor Lower Right Duct Air Temperature Sensor Upper Right Duct Air Temperature Sensor A/C Evaporator Temperature Sensor Lower Auxiliary Duct Air Temperature Sensor Upper Auxiliary Duct Air Temperature Sensor If not within 10% of ambient temperature Refer to «DTC B0173, B0178, B0509, B0514, B0519, B3583, or B3933»(/cadillac/srx/ii-2012-2016/remont/automatic-hvac-system/#hvac-system-automatic) . If within 10% of ambient temperature
  11. Verify the scan tool parameters listed below are within 10% of actual conditions. Passenger Compartment Humidity Passenger Compartment Humidity Sensor Temperature Passenger Compartment Windshield Temperature If not within 10% of actual conditions Refer to «DTC B018A, B048C, B048F, or B1395»(/cadillac/srx/ii-2012-2016/remont/automatic-hvac-system/#hvac-system-automatic) . If within 10% of actual conditions
  12. Engine ON, A/C system ON.
  13. Verify cool air flows from the ducts with the temperature control in the coldest position. If the air is not cool Verify the Q2 A/C Compressor Clutch is engaged. If the Q2 A/C Compressor Clutch is not engaged, refer to «Air Conditioning Compressor Malfunction»(/cadillac/srx/ii-2012-2016/remont/automatic-hvac-system/#hvac-system-automatic) . If the Q2 A/C Compressor Clutch is engaged, refer to «Air Conditioning (A/C) System Performance Test (LF1 or LFX)»(/cadillac/srx/ii-2012-2016/remont/automatic-hvac-system/#heating-ventilation-and-air-conditioning) , and «DTC B393B»(/cadillac/srx/ii-2012-2016/remont/automatic-hvac-system/#hvac-system-automatic) . If the air is cool
  14. Verify warm air flows from the ducts with the temperature control in the warmest position. If the air is not warm Refer to «Heating Performance Diagnostic»(/cadillac/srx/ii-2012-2016/remont/automatic-hvac-system/#heating-ventilation-and-air-conditioning__heating-performance-diagnostic) . If the air is warm
  15. Engine OFF, ignition ON.
  16. Verify the Air Quality Sensor parameter changes while introducing hydrocarbons from a suitable source into the vicinity of the B108 Air Quality Sensor. If the Air Quality Sensor parameter does not change Refer to «DTC B3843»(/cadillac/srx/ii-2012-2016/remont/automatic-hvac-system/#hvac-system-automatic) . If the Air Quality Sensor parameter changes
  17. Verify the scan tool Sunload parameter changes while covering the B10B Ambient Light/Sunload Sensor with a shop towel and changes when shining a bright light on it. If the Sunload parameter does not change Refer to «DTC B0163, B0183, or B1405»(/cadillac/srx/ii-2012-2016/remont/automatic-hvac-system/#hvac-system-automatic) . If the Sunload parameter changes
  18. Verify the actual inside air temperature, using a thermometer, is less than 3°C (5°F) difference from the scan tool Inside Passenger Compartment Air Temp. Sensor parameter. If greater than a 3°C (5°F) difference Refer to «DTC B0163, B0183, or B1405»(/cadillac/srx/ii-2012-2016/remont/automatic-hvac-system/#hvac-system-automatic) . If less than a 3°C (5°F) difference
  19. All OK.

Perform the Diagnostic Repair Verification after completing the repair.

  1. «HVAC Component Replacement Reference»(/cadillac/srx/ii-2012-2016/remont/automatic-hvac-system/#hvac-system-automatic__hvac-component-replacement-reference)
  2. «Control Module References»(/cadillac/srx/ii-2012-2016/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for HVAC control module replacement, programming and setup
  1. Perform the «Diagnostic System Check - Vehicle»(/cadillac/srx/ii-2012-2016/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures) prior to using this diagnostic procedure.
  2. Review «Strategy Based Diagnosis»(/cadillac/srx/ii-2012-2016/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»(/cadillac/srx/ii-2012-2016/remont/oem-general-information/#vehicle-diagnostic-information-diagnostic-information-and-procedures__diagnostic-procedure-instructions) provides an overview of each diagnostic category.

The A/C compressor uses a conventional belt driven magnetic clutch to engage and mechanically turn the compressor. When the A/C switch is pressed, the HVAC control module sends an A/C request message to the ECM via serial data. If specific criteria is met, the ECM then grounds the A/C compressor clutch relay control circuit, which will switch the A/C compressor clutch relay. With the relay contacts closed, battery voltage is supplied to the permanently grounded A/C compressor clutch. The A/C compressor clutch will then be activated.

This A/C system utilizes a variable displacement solenoid valve to alter the amount of displacement created by the turning of the compressor. The HVAC control module provides both battery voltage and a pulse width modulated ground to the variable displacement solenoid valve. When the A/C switch is pressed, the HVAC control module grounds the variable displacement solenoid using a (PWM) signal in order to determine the amount of compressor displacement. The performance of the A/C compressor is regulated based on the adjusted interior temperature.

The following conditions must be met in order to turn on the A/C compressor

  1. Battery voltage is between 9-18 V.
  2. Engine coolant temperature is less than 124°C (255°F).
  3. Engine speed is greater than 600 RPM.
  4. Engine speed is less than 5 500 RPM.
  5. A/C high side pressure is between 269-2 929 kPa (39-425 PSI).
  6. Throttle position is less than 100%.
  7. Evaporator temperature is greater than 3°C (38°F).
  8. ECM does not detect excessive torque load.
  9. ECM does not detect insufficient idle quality.
  10. The ambient temperature is above 1°C (34°F).
  11. Blower motor is ON.

Schematic Reference

Connector End View Reference

Description and Operation

Electrical Information Reference

  1. «Circuit Testing»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__circuit-testing)
  2. «Connector Repairs»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__connector-repairs)
  3. «Testing for Intermittent Conditions and Poor Connections»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__testing-for-intermittent-conditions-and-poor)
  4. «Wiring Repairs»(/cadillac/srx/ii-2012-2016/remont/body-electrical/#wiring-systems-and-power-management-diagnostic-information-and-procedures__wiring-repairs)

Scan Tool Reference

Control Module References for scan tool information

Note. Refer to HVAC System Malfunction before performing this procedure.

  1. Ignition ON, press and release the A/C Switch.
  2. Verify the HVAC control module scan tool A/C Request Signal parameter changes between Active and Inactive. If the parameter does not change Replace the A20 Radio/HVAC Controls. If the parameter changes
  3. Set A/C system to coolest setting with blower ON.
  4. Press and release the A/C switch several times.
  5. Verify the ECM scan tool A/C Request Signal parameter changes between Active and Inactive. If the parameter does not change Replace the K33 HVAC Control Module. If the parameter changes
  6. Verify the A/C compressor clutch engages when commanding the ECM A/C Relay output function On and Off with a scan tool. If the A/C compressor clutch does not engage Refer to «DTC P0645, P0646, or P0647»(/cadillac/srx/ii-2012-2016/remont/automatic-hvac-system/#hvac-system-automatic) If the A/C compressor clutch engages
  7. Engine ON.
  8. Verify the HVAC control module scan tool A/C Compressor Refrigerant Solenoid Valve Command parameter changes with varying cooling loads. If the parameter does not change Refer to «DTC B393B»(/cadillac/srx/ii-2012-2016/remont/automatic-hvac-system/#hvac-system-automatic) If the parameter does change
  9. All OK.

Perform the Diagnostic Repair Verification after completing the repair.

  1. «HVAC Component Replacement Reference»(/cadillac/srx/ii-2012-2016/remont/automatic-hvac-system/#hvac-system-automatic__hvac-component-replacement-reference)
  2. «Control Module References»(/cadillac/srx/ii-2012-2016/remont/communication-devices/#programming-and-setup-all-systems__control-module-references) for HVAC control module replacement, programming and setup

Afterblow Enabling

The afterblow mode can be enabled using the scan tool. The afterblow mode allows the blower motor to operate after the engine has been turned off. This operation of the blower motor dries the evaporator core, which reduces the amount of microbial growth which can create undesirable odors.

Use the following procedure in order to enable the afterblow mode

  1. Connect the Scan Tool.
  2. Turn ON the ignition, with the engine OFF.
  3. Build the vehicle with the scan tool.
  4. Select Module Diagnosis.
  5. Select Remote Heater and Air Conditioning Control Module.
  6. Select Configuration/Reset Functions.
  7. Select HVAC Afterblow Configuration.

When afterblow has been enabled by the scan tool the blower motor will operate at 68% blower speed, following the sequence below up to 5 times. This could last up to an hour

  1. The blower motor will be OFF for 7-11 minutes.
  2. The blower motor will RUN for 25-30 seconds.

The following conditions must be met for the HVAC module to operate the afterblow

  1. The engine must be turned off for at least 30 min.
  2. The outside air temperature must be at least 21°C (70°F).
  3. The A/C compressor must have operated for more than 2 minutes before shut down during the latest key cycle.
  4. The system voltage must be at least 12 V.

HVAC Control Module Replacement

When replacing or disconnecting the HVAC control module, it will be necessary to perform a recalibration process. When installing or reconnecting the HVAC control module, be sure to perform the following

Preferred Method (with Scan Tool)

Note. Do not adjust any controls on the HVAC control module while the HVAC control module is self-calibrating. If interrupted, improper HVAC performance will result.

  1. Ignition OFF.
  2. Disconnect the scan tool.
  3. Install/connect the HVAC control module.
  4. Connect all previously disconnected components.
  5. Start the vehicle.
  6. With the scan tool, initiate the HVAC Actuators Learn feature of the HVAC control module Special Functions menu.
  7. Operate system and verify that no DTCs have set as current DTCs.
  8. If DTC B101E 4B is set after attempting the actuator recalibration procedure, perform the following: Verify which actuator does not have a scan tool learn status parameter status of complete. Verify the unlearned actuator is physically rotating - A common cause of DTC B101E 4B is an actuator that is electrically OK but fails to physically rotate (e.g. stripped gears). If the unlearned actuator is not physically rotating, replace the actuator, otherwise replace the HVAC control module.

Alternate Method (without Scan Tool)

  1. Clear all DTCs.
  2. Ignition OFF.
  3. Install/connect the HVAC control module.
  4. Connect all previously disconnected components.
  5. Remove the HVAC control module fuse for a minimum of 10 s.
  6. Install the HVAC control module fuse.
  7. Start the vehicle.
  8. Wait 40 s for the HVAC control module to self-calibrate.

Actuator Replacement

When replacing an HVAC actuator it will be necessary to allow the HVAC control module to perform a recalibration process. When installing an HVAC actuator be sure to perform one of the following

Preferred Method (with Scan Tool)

  1. Clear all DTCs.
  2. Ignition OFF.
  3. Install the HVAC actuator.
  4. Connect all previously disconnected components.
  5. Start the vehicle.
  6. With the scan tool, initiate the HVAC Actuators Relearn feature of the HVAC control module Special Functions menu.
  7. Operate system and verify that no DTCs have set as current DTCs.
  8. If DTC B101E 4B is set after attempting the actuator recalibration procedure, perform the following: Verify which actuator does not have a scan tool learn status parameter status of complete. Verify the unlearned actuator is physically rotating - A common cause of DTC B101E 4B is an actuator that is electrically OK but fails to physically rotate (e.g. stripped gears). If the unlearned actuator is not physically rotating, replace the actuator, otherwise replace the HVAC control module.

Alternate Method (without Scan Tool)

  1. Clear all DTCs.
  2. Ignition OFF.
  3. Install the HVAC actuator.
  4. Connect all previously disconnected components.
  5. Remove the HVAC control module fuse for a minimum of 10 s.
  6. Install the HVAC control module fuse.
  7. Start the vehicle.
  8. Wait 40 s for the HVAC control module to self-calibrate.

Scheme 52

Scheme 52: Heater and Air Conditioning Control Replacement
Scheme 52: Heater and Air Conditioning Control Replacement
CalloutComponent Name
Preliminary Procedure Remove the radio assembly. Refer to Radio Replacement .
1Heater and Air Conditioning Remote Control Procedure Disconnect the control harness electrical connectors. Release the retainers in order to remove the control. Program the control module. Refer to Control Module References .

Heater and Air Conditioning Control Replacement

Scheme 53

Scheme 53: Heater and Blower and Air Conditioning Control Module Replacement
Scheme 53: Heater and Blower and Air Conditioning Control Module Replacement
CalloutComponent Name
Preliminary Procedure Remove the instrument panel compartment . Refer to Instrument Panel Compartment Replacement . Disconnect the heater and blower and air conditioning control module electrical connectors.
1Heater and Blower and Air Conditioning Control Module Screws (Qty: 2) CAUTION: Refer to Fastener Caution . Tighten 1.5 N.m (13 lb in)
2Heater and Blower and Air Conditioning Control Module
CAUTION
Refer to Fastener Caution .

Heater and Blower and Air Conditioning Control Module Replacement

Scheme 54

Scheme 54: Auxiliary Heater and Air Conditioning Control Module Replacement
Scheme 54: Auxiliary Heater and Air Conditioning Control Module Replacement
CalloutComponent Name
Preliminary Procedure Remove the floor console. Refer to Front Floor Console Replacement . Disconnect the auxiliary heater and blower and air conditioning control module electrical connectors.
1Auxiliary Heater and Blower and Air Conditioning Control Module Screws (Qty: 2) CAUTION: Refer to Fastener Caution . Tighten 1.5 N.m (13 lb in)
2Auxiliary Heater and Blower and Air Conditioning Control Module
CAUTION
Refer to Fastener Caution .

Auxiliary Heater and Air Conditioning Control Module Replacement

Scheme 55

Scheme 55: Air Inlet Valve Actuator Replacement - Left Side
Scheme 55: Air Inlet Valve Actuator Replacement - Left Side
CalloutComponent Name
Preliminary Procedures Disconnect the negative battery cable. Refer to Battery Negative Cable Disconnection and Connection . Remove the Instrument Panel Assembly. Refer to Instrument Panel Assembly Removal . Remove the inside air inlet actuator- Left. Refer to Air Inlet Valve Actuator Replacement - Left Side .
1Air Inlet Valve Actuator Screw (Qty: 2) CAUTION: Refer to Fastener Caution . Tighten 1.5 N.m (13 lb in)
2Air Inlet Valve Actuator Procedure Disconnect the air inlet valve actuator electrical connector. TIP: Actuator is self-calibrating when connecting the battery.
CAUTION
Refer to Fastener Caution .

Air Inlet Valve Actuator Replacement - Left Side

Scheme 56

Scheme 56: Air Inlet Valve Actuator Replacement - Right Side
Scheme 56: Air Inlet Valve Actuator Replacement - Right Side
CalloutComponent Name
Preliminary Procedures Disconnect the negative battery cable. Refer to Battery Negative Cable Disconnection and Connection . Remove the Instrument panel assembly. Refer to Instrument Panel Assembly Removal . Remove the inside air inlet actuator- Left. Refer to Air Inlet Valve Actuator Replacement - Left Side .
1Air Inlet Valve Actuator Screw (Qty: 2) CAUTION: Refer to Fastener Caution . Tighten 1.5 N.m (13 lb in)
2Air Inlet Valve Actuator Procedure Disconnect the air inlet valve actuator electrical connector. TIP: Actuator is self-calibrating when connecting the battery.
CAUTION
Refer to Fastener Caution .

Air Inlet Valve Actuator Replacement - Right Side

Scheme 57

Scheme 57: Mode Control Cam Actuator Replacement
Scheme 57: Mode Control Cam Actuator Replacement
CalloutComponent Name
Preliminary Procedures Disconnect the negative battery cable. Refer to Battery Negative Cable Disconnection and Connection . Remove the instrument panel side trim panel. Refer to Instrument Panel Side Trim Panel Replacement . Remove the instrument panel insulator panel. Refer to Instrument Panel Insulator Panel Replacement - Left Side . Remove the driver knee bolster panel. Refer to Driver Knee Bolster Panel Replacement . Remove the driver knee bolster reinforcement. Refer Driver Knee Bolster Reinforcement Replacement .
1Mode Cam Actuator Cover Screw (Qty: 1) CAUTION: Refer to Fastener Caution . Procedure Disconnect the mode actuator electrical connector. Tighten 1.5 N.m (13 lb in)
2Mode Cam Actuator Cover.
3Mode Cam Actuator Gears
4Mode Cam Actuator Screw (Qty: 2) Tighten 1.5 N.m (13 lb in)
5Mode Cam Actuator NOTE: Actuator is self-calibrating when connecting the battery.
CAUTION
Refer to Fastener Caution .
NOTE
Actuator is self-calibrating when connecting the battery.

Mode Control Cam Actuator Replacement

Removal Procedure

  1. Remove the mode came gear cover screw (1) and cover (2).
  2. Remove the mode cam gear actuator screws (1) and separate the actuator (2) from the HVAC module.
  3. Disconnect the mode cam gear actuator electrical connector.
  4. Remove the mode cam gear (1) from the HVAC module.
  5. For alignment purposes, remove both cam gear levers (2).
  6. If the valve gears (3) are damaged, remove them from the HVAC module and discard.

Installation Procedure

  1. If the valve gears were removed or replaced, install them onto the HVAC module.
  2. Rotate the defroster gear clockwise (1) as far as it will go, and install the lever by engaging a gear tooth into the rightmost lever gap (2).
  3. Rotate the heater door gear clockwise (1) as far as it will go, and install the lever by engaging a gear tooth into the rightmost lever gap (2).
  4. Install the mode cam into position on the levers.
  5. Continue to push the mode cam onto the case and rotate left and/or right until an audible click is heard locking the mode cam in place.
  6. Rotate the mode cam from stop to stop (1). It should rotate completely without binding. If the mode does not rotate from stop to stop, then remove the mode came and levers and repeat steps 2-6.
  7. Place the mode cam actuator and gear assembly (2) on the HVAC module and install the screws (1) and tighten to 1.7 N.m (5 lb in).
  8. Connect the mode cam actuator electrical connector.
  9. Install the cam gear cover (1) and screw (2).

Scheme 58

Scheme 58: Temperature Valve Actuator Replacement - Right Side
Scheme 58: Temperature Valve Actuator Replacement - Right Side
CalloutComponent Name
Preliminary Procedures Disconnect the negative battery cable. Refer to Battery Negative Cable Disconnection and Connection . Remove the instrument panel lower trim panel. Refer to Instrument Panel Lower Trim Panel Replacement - Right Side .
1Temperature Valve Actuator Screw (Qty: 2) CAUTION: Refer to Fastener Caution . Tighten 1.5 N.m (13 lb in)
2Temperature Valve Actuator Procedure Disconnect the temperature actuator electrical connector. TIP: Actuator is self-calibrating when connecting the battery.
CAUTION
Refer to Fastener Caution .

Temperature Valve Actuator Replacement - Right Side

Scheme 59

Scheme 59: Temperature Valve Actuator Replacement - Left Side
Scheme 59: Temperature Valve Actuator Replacement - Left Side
Call outComponent Name
Preliminary Procedures Disconnect the negative battery cable. Refer to Battery Negative Cable Disconnection and Connection . Remove the left side instrument panel insulator panel. Refer to Instrument Panel Insulator Panel Replacement - Left Side .
1Temperature Valve Actuator Screw (Qty: 3) CAUTION: Refer to Fastener Caution . Tighten 1.5 (13 lb in)
2Temperature Valve Actuator Procedures Disconnect the temperature actuator electrical connector. Perform the actuator re-calibration procedure. Refer to Actuator Recalibration
CAUTION
Refer to Fastener Caution .

Temperature Valve Actuator Replacement - Left Side

Scheme 60

Scheme 60: Auxiliary Temperature Valve Actuator Replacement
Scheme 60: Auxiliary Temperature Valve Actuator Replacement
CalloutComponent Name
Preliminary Procedures Disconnect the negative battery cable. Refer to Battery Negative Cable Disconnection and Connection . Remove front floor console extension. Refer to Front Floor Console Extension Replacement
1Auxiliary Temperature Valve Actuator Screw (Qty: 2) CAUTION: Refer to Fastener Caution . Tighten 1.5 N.m (13 lb in)
2Auxiliary Temperature Valve Actuator Procedure Disconnect the temperature actuator electrical connector. TIP: Actuator is self-calibrating when connecting the battery.
CAUTION
Refer to Fastener Caution .

Auxiliary Temperature Valve Actuator Replacement

Scheme 61

Scheme 61: Auxiliary Mode Valve Actuator Replacement
Scheme 61: Auxiliary Mode Valve Actuator Replacement
CalloutComponent Name
Preliminary Procedures Disconnect the negative battery cable. Refer to Battery Negative Cable Disconnection and Connection . Remove front floor console extension. Refer to Front Floor Console Extension Replacement
1Inside Air Valve Actuator Screw (Qty: 3) CAUTION: Refer to Fastener Caution . Tighten 1.5 N.m (13 lb in)
2Inside Air Valve Actuator Procedure Disconnect the recirculation actuator electrical connector. TIP: Actuator is self-calibrating when connecting the battery.
CAUTION
Refer to Fastener Caution .

Auxiliary Mode Valve Actuator Replacement

Scheme 62

Scheme 62: Duct Air Temperature Sensor Replacement - Upper
Scheme 62: Duct Air Temperature Sensor Replacement - Upper
CalloutComponent Name
Preliminary Procedure Remove the left front floor console extension. Refer to Front Floor Console Extension Replacement .
1Duct Air Temperature Sensor - Auxiliary Upper Procedures Disconnect the auxiliary upper duct air temperature sensor connector. To remove the auxiliary upper duct air temperature sensor, turn the auxiliary upper duct air temperature sensor counter clock wise a quarter of a turn.

Duct Air Temperature Sensor Replacement - Upper

Scheme 63

Scheme 63: Duct Air Temperature Sensor Replacement - Upper Right Side
Scheme 63: Duct Air Temperature Sensor Replacement - Upper Right Side
CalloutComponent Name
Preliminary Procedures Disconnect the negative battery cable. Refer to Battery Negative Cable Disconnection and Connection . Remove the instrument panel assembly. Refer to Instrument Panel Assembly Removal .
1Duct Air Temperature Sensor- Upper Right Side Procedure Disconnect the air temperature sensor electrical connector. Twist and pull the upper air temperature sensor from the HVAC module assembly.

Duct Air Temperature Sensor Replacement - Upper Right Side

Scheme 64

Scheme 64: Duct Air Temperature Sensor Replacement - Upper Left Side
Scheme 64: Duct Air Temperature Sensor Replacement - Upper Left Side
CalloutComponent Name
Preliminary Procedure Remove the instrument panel assembly. Refer to Instrument Panel Assembly Removal .
1Duct Air Temperature Sensor Replacement- Upper Left Side Procedure Disconnect the air temperature sensor electrical connector. Twist and pull the lower air temperature sensor from the HVAC module assembly.

Duct Air Temperature Sensor Replacement - Upper Left Side

Scheme 65

Scheme 65: Duct Air Temperature Sensor Replacement - Lower
Scheme 65: Duct Air Temperature Sensor Replacement - Lower
CalloutComponent Name
Preliminary Procedure Remove the auxiliary blower motor assembly. Refer to Auxiliary Blower Motor Replacement .
1Duct Air Temperature Sensor - Auxiliary Lower Procedures Disconnect the auxiliary lower duct air temperature sensor connector. To remove the auxiliary lower duct air temperature sensor, turn the auxiliary lower duct air temperature sensor counter clock wise a quarter of a turn.

Duct Air Temperature Sensor Replacement - Lower

Scheme 66

Scheme 66: Duct Air Temperature Sensor Replacement - Lower Left Side
Scheme 66: Duct Air Temperature Sensor Replacement - Lower Left Side
CalloutComponent Name
Preliminary Procedure Remove instrument panel insulator panel- left side. Refer to Instrument Panel Insulator Panel Replacement - Left Side .
1Duct Air Temperature Sensor- Lower Left Side Procedure Disconnect the air temperature sensor electrical connector. Twist and pull the lower duct air temperature sensor from the HVAC module assembly.

Duct Air Temperature Sensor Replacement - Lower Left Side

Scheme 67

Scheme 67: Duct Air Temperature Sensor Replacement - Lower Right Side
Scheme 67: Duct Air Temperature Sensor Replacement - Lower Right Side
CalloutComponent Name
Preliminary Procedure Remove the instrument panel compartment. Refer to Instrument Panel Compartment Replacement .
1Duct Air Temperature Sensor Replacement- Lower Right Side Procedure Disconnect the duct air temperature sensor electrical connector. Twist and pull the duct air temperature sensor from the HVAC module assembly.

Duct Air Temperature Sensor Replacement - Lower Right Side

Scheme 68

Scheme 68: Ambient Air Quality Sensor Replacement
Scheme 68: Ambient Air Quality Sensor Replacement
CalloutComponent Name
Preliminary Procedure Remove the air inlet grille panel. Refer to Air Inlet Grille Panel Replacement .
1Ambient Air Quality Sensor Procedures Unsnap the ambient air quality sensor and move it forward. Disconnect the electrical connector.

Ambient Air Quality Sensor Replacement

Scheme 69

Scheme 69: Inside Air Temperature Sensor Replacement
Scheme 69: Inside Air Temperature Sensor Replacement
CalloutComponent Name
Preliminary Procedure Remove auxiliary blower motor. Refer to Auxiliary Blower Motor Replacement . Disconnect the inside air temperature sensor electrical connectors.
1Inside AirTemperature Sensor Procedure Disconnect the duct air temperature sensor electrical connector. Twist and pull the duct air temperature sensor from the HVAC module assembly.

Inside Air Temperature Sensor Replacement

Scheme 70

Scheme 70: Inside Air Moisture and Windshield Temperature Sensor Replacement
Scheme 70: Inside Air Moisture and Windshield Temperature Sensor Replacement
CalloutComponent Name
Preliminary Procedure Remove the inside rearview mirror mount cover Inside Rearview Mirror Replacement .
1Inside Air Moisture and Windshield Temperature Sensor Retainer Procedure Disconnect the electrical connector Release the inside air moisture and windshield temperature sensor retainer.

Inside Air Moisture and Windshield Temperature Sensor Replacement

Automatic HVAC Description and Operation

The air temperature and the air delivery description and operation are divided into eight areas

  1. HVAC Control Components
  2. Air Speed (Front)
  3. Air Speed (Rear)
  4. Air Delivery (Front)
  5. Air Delivery (Rear)
  6. Heating and A/C Operation
  7. Recirculation Operation
  8. Automatic Operation
  9. Engine Coolant
  10. A/C Cycle

HVAC Control Components

Radio/HVAC Control

The Radio/HVAC control contains all switches, which are required to control the functions of HVAC and serve as interface between the operator and the HVAC control module. The selected values are passed to the HVAC control module via LIN-Bus.

Radio/HVAC Control - Auxiliary (CJ4 only)

The Radio/HVAC control - auxiliary contains all switches, which are required to control the functions of rear HVAC and serve as interface between the operator and the HVAC control module. The selected values are passed to the HVAC control module via LIN-Bus.

HVAC Control Module

The HVAC control module is a GMLAN device that interfaces between the operator and the HVAC system to maintain and control desired air temperature and air distribution settings. The battery positive voltage circuit provides power that the HVAC control module uses for keep alive memory. If the battery positive voltage circuit loses power, all HVAC DTCs and settings will be erased from keep alive memory. The body control module (BCM), which is the vehicle mode master, provides a device ON-Signal. The HVAC control module provides blower, air delivery mode and air temperature settings.

The HVAC control module supports the following features

FeatureAvailability
AfterblowAvailable if reprogrammed by the technician
PurgeYes
PersonalizationYes
Actuator CalibrationYes

Mode Actuator (Front)

The mode actuator is a 5-wire stepper motor. The HVAC control module supplies a 12 V reference voltage to the stepper motor and energizes the 4 stepper motor coils with a pulsed ground signal. The stepper motor puts the mode flap into the calculated position in order to reach the selected position. The null point of the stepper motor will be calibrated, if the stepper motor is new. When the stepper motor is calibrated, the HVAC control module can drive the applicable coil to reach exactly the desired position of the flap.

Mode Actuator - Rear (CJ4 only)

The mode actuator is a 5-wire stepper motor. The HVAC control module supplies a 12 V reference voltage to the stepper motor and energizes the 4 stepper motor coils with a pulsed ground signal. The stepper motor puts the mode flap into the calculated position in order to reach the selected position. The null point of the stepper motor will be calibrated, if the stepper motor is new. When the stepper motor is calibrated, the HVAC control module can drive the applicable coil to reach exactly the desired position of the flap.

Air Temperature Actuators (Front)

The interior temperature can be selected separately for the driver and passenger. For this purpose, two stepper motors are used that regulates two mixed air flaps independently of each other. The air temperature actuators are 5-wire stepper motors. The HVAC control module supplies a 12 V reference voltage to each stepper motor and energizes the 4 stepper motor coils with a pulsed ground signal. The left air temperature actuator moves the left mixed air flap into the calculated position, in order to reach the selected temperature of the left temperature switch. The right air temperature actuator puts the right mixed air flap into the calculated position, in order to reach the selected temperature of the right temperature switch. The null point of the stepper motor will be calibrated, if the stepper motor is new. When the stepper motor is calibrated, the HVAC control module can drive the applicable coil to reach exactly the desired position of the flap.

Air Temperature Actuator - Rear (CJ4 only)

The interior temperature can be selected separately for the rear passengers. The air temperature door actuator - auxiliary is a 5-wire stepper motor. The HVAC control module supplies a 12 V reference voltage to the stepper motor and energizes the 4 stepper motor coils with a pulsed ground signal. The air temperature door actuator - auxiliary moves the rear mixed air flap into the calculated position, in order to reach the selected temperature of the rear temperature switches. The null point of the stepper motor will be calibrated, if the stepper motor is new. When the stepper motor is calibrated, the HVAC control module can drive the applicable coil to reach exactly the desired position of the flap.

Recirculation Actuator

The recirculation actuator is a 5-wire stepper motor. The HVAC control module supplies a 12 V reference voltage to the stepper motor and energizes the 4 stepper motor coils with a pulsed ground signal. The stepper motor puts the recirculation flap into the calculated position in order to reach the desired position. The null point of the stepper motor will be calibrated, if the stepper motor is new. When the stepper motor is calibrated, the HVAC control module can drive the applicable coil to reach exactly the desired position of the flap.

Air Inlet Actuator

The air inlet actuator is a 5-wire stepper motor. The HVAC control module supplies a 12 V reference voltage to the stepper motor and energizes the 4 stepper motor coils with a pulsed ground signal. The stepper motor moves the air inlet flap into the calculated position, in order to reach the selected position. The null point of the stepper motor will be calibrated, if the stepper motor is new. When the stepper motor is calibrated, the HVAC control module can drive the applicable coil to reach exactly the desired position of the flap.

Blower Motor Control Processor (Front)

The blower motor control processor controls the speed of the blower motor by increasing or decreasing the voltage drop on the ground side of the blower motor. The HVAC control module provides a low side pulse width modulation (PWM) signal to the blower motor control processor via the blower motor speed control circuit. As the requested blower speed increases, the HVAC control module increases the amount of time that the speed signal is modulated to ground. As the requested blower speed decreases, the HVAC control module decreases the amount of time that the signal is modulated to ground.

Blower Motor Control Processor - Rear (CJ4 only)

The blower motor control processor controls the speed of the blower motor by increasing or decreasing the voltage drop on the ground side of the blower motor. The HVAC control module provides a low side pulse width modulation (PWM) signal to the blower motor control processor via the blower motor speed control circuit. As the requested blower speed increases, the HVAC control module increases the amount of time that the speed signal is modulated to ground. As the requested blower speed decreases, the HVAC control module decreases the amount of time that the signal is modulated to ground.

Duct Temperature Sensors

The air temperature sensors are 2-wire negative temperature co-efficient thermistors. The sensors operate within a temperature range of -40 to +85°C (-40 to +185°F). The sensors are installed in the air distribution ducts and measure the temperature of the air that streams from the ducts. The HVAC control module uses these values to calculate the mixed air flap position.

Evaporator Temperature Sensor

The evaporator temperature sensor is a 2-wire negative temperature co-efficient thermistor. The sensor operates within a temperature range of -40 to +85°C (-40 to +185°F). The sensor is installed at the evaporator and measures its temperature. If the temperature drops under 3°C (38°F), the compressor will be switched off in order to prevent a frozen evaporator.

A/C Refrigerant Pressure Sensor

The A/C refrigerant pressure sensor is a 3-wire piezoelectric pressure transducer. A 5 V reference voltage, low reference, and signal circuits enable the sensor to operate. The A/C pressure signal can be between 0.2-4.8 V. When the A/C refrigerant pressure is low, the signal value is near 0 V. When the A/C refrigerant pressure is high, the signal value is near 5 V. The engine control module (ECM) converts the voltage signal to a pressure value. When pressure is too high or too low, the ECM will not allow the A/C compressor clutch to engage.

A/C Compressor

The A/C compressor is constantly belt driven. The performance of the A/C compressor is regulated per a lifting magnet in the A/C compressor. The HVAC control module supplies battery voltage to the A/C compressor. When the A/C switch is pressed, the HVAC control module provides a pulse width modulation (PWM) signal to the A/C compressor in order to command the performance of the A/C compressor. The performance of the A/C compressor is regulated according to adjusted interior temperature on the basis of characteristic lines. Therefore the HVAC control module grounds the A/C compressor with the PWM signal.

Windshield Temperature and Inside Moisture Sensor

The windshield temperature and inside moisture sensor includes the relative humidity sensor, windshield temperature sensor and humidity sensing element temperature sensor.

This sensor assembly provides information about

  1. Relative humidity level at windshield (compartment side)
  2. Temperature of the windshield inside (compartment side)
  3. Temperature of the humidity sensor element

The relative humidity sensor measures the relative humidity of the compartment side of the windshield. It also detects the temperature of the windshield surface on the passenger compartment side. Both values are used as control inputs for the HVAC control module application to calculate the fog risk on windshield compartment side and ability to reduce fuel consumption by decreasing A/C compressor power to a minimum without causing any fog. The sensor will also enable partial recirculation mode in order to improve heat-up performance of the passenger compartment under cold ambient temperature conditions without the risk of mist build-up on the windshield. The humidity sensor element temperature sensor supplies the temperature of the humidity sensor element. It is only needed if the thermal contact between the humidity sensing element and the inside windshield surface is not sufficient.

Ambient Light/Sunload Sensor

The ambient light/sunload sensor includes the sunload sensor and passenger compartment temperature sensor.

This sensor assembly provides information about

  1. Sun heat intensity
  2. Elevation
  3. Azimuth
  4. Passenger compartment temperature

The sunload sensor is connected to ground and to a 12 V clocked power supply through the HVAC control module. This clocked power supply is to power the sensor electronics and to work as a clock generator to the sunload sensor micro controller. The sensor uses a pulse signal for data identification and transferring the sun intensity measurement. At each positive transition from the clocked supply input, the sunload sensor micro controller will shift channels enabling new intensity measurement on the signal output to the HVAC control module. The signal voltage varies between 0-4 V.

The passenger compartment temperature sensor is a negative temperature co-efficient thermistor. A signal and low reference circuit enables the sensor to operate. As the air temperature increases, the sensor resistance decreases. The sensor signal varies between 0-5 V.

Bright or high intensity light causes the vehicles interior temperature to increase. The HVAC system compensates for the increased temperature by diverting additional cool air into the vehicle.

Air Speed (Front)

The blower control switch is part of the Radio/HVAC control. The selected value of the blower switch position is sent to the HVAC control module via LIN-Bus.

The blower motor control module is an interface between HVAC control module and blower motor. The blower motor control module regulates supply voltage and ground circuits to blower motor. The HVAC control module provides a PWM signal to the blower motor control module in order to command the desired blower motor speed. The blower motor control module supplies battery voltage to the blower motor and uses the blower motor ground as a low side control to adjust the blower motor speed. The voltage amounts between 2-13 V and changes linear to the height of the PWM signal.

Air Speed - Rear (CJ4)

The blower control switches are part of the Radio/HVAC control - auxiliary. The selected value of the rear blower switches position is sent to the HVAC control module via LIN-Bus.

The blower motor control module - auxiliary is an interface between HVAC control module and blower motor - auxiliary. The blower motor control module - auxiliary regulates supply voltage and ground circuits to blower motor - auxiliary. The HVAC control module provides a PWM signal to the blower motor control module - auxiliary in order to command the desired blower motor speed. The blower motor control module - auxiliary supplies battery voltage to the blower motor - auxiliary and uses the blower motor - auxiliary ground as a low side control to adjust the blower motor speed. The voltage amounts between 2-13 V and changes linear to the height of the PWM signal.

Air Delivery (Front)

The HVAC control module controls the distribution of air by the use of recirculation and mode door actuator. The modes that may be selected are

  1. Defrost
  2. Defog
  3. Panel
  4. Floor

The desired air distribution mode can be selected with the air distribution switches at the Radio/HVAC control. The Radio/HVAC control delivers the values to the HVAC control module via LIN-Bus. The HVAC control module controls the mode door actuator so that it drives the flap to the calculated position. Depending on the position of the flap, air is distributed through various ducts leading to the outlets in the dash. Turning the mode flap to the defrost position, the HVAC control module will move the recirculation actuator to outside air, reducing window fogging. When defrost is selected, the blower motor will be activated, regardless of the coolant temperature. The HVAC control module enables a high volume of air delivered to the front defrost vents. A/C is available in all modes.

The rear window defogger does not affect the HVAC system.

Air Delivery - Rear (CJ2)

Rear air delivery does not include an auxiliary blower, rear controls, or actuators such as Mode and Temperature. It uses only the vents in the console between and under the two front seats. The air temperature and mode from the rear ducts will match the temperature and mode that is chosen for the driver, and when air is directed to the windshield for defrost it will be blocked from the rear ducts.

Air Delivery - Rear (CJ4)

The HVAC control module controls the distribution of air by the mode door actuator - auxiliary. The modes that may be selected are

  1. AUTO
  2. Floor
  3. Bi-Level
  4. Vent

The desired rear air distribution mode can be selected with the Mode switch at the Radio/HVAC control - auxiliary. The Radio/HVAC control - auxiliary delivers the values to the HVAC control module via LIN-Bus. The HVAC control module controls the mode door actuator - auxiliary so that it drives the flap to the calculated position. Depending on the position of the flap, air is distributed through various ducts.

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. 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. Blower motor speed setting
  4. Mode setting

When the A/C switch or the AUTO switch is pressed, the Radio/HVAC control sends a signal to the HVAC control module via LIN-Bus. The HVAC control module evaluates this signal and sends an A/C request signal to the ECM via CAN-Bus. The ECM checks all preconditions before releasing and if all conditions are met sends a release signal back to the HVAC control module. The A/C compressor is activated by the HVAC control module. The HVAC control module supplies battery voltage to the A/C compressor. When the A/C switch is pressed, the HVAC control module provides a pulse width modulation (PWM) signal to the A/C compressor in order to command the performance of the A/C compressor. The performance of the A/C compressor is regulated according to adjusted interior temperature on the basis of characteristic lines. Therefore the HVAC control module grounds the A/C compressor with the PWM signal.

The following conditions must be met in order to activate the A/C compressor

  1. Battery voltage is between 9-18 V
  2. Engine coolant temperature is less than 124°C (255°F)
  3. Engine speed is greater than 600 RPM
  4. Engine speed is less than 5 500 RPM
  5. A/C high side pressure is between 269-2 929 kPa (39-425 PSI)
  6. Throttle position is less than 100%
  7. Evaporator temperature is greater than 3°C (38°F)
  8. ECM does not detect immoderate torque load
  9. ECM does not detect insufficient idle quality
  10. The ambient temperature is above 1°C (34°F)

The sensor information is used by the ECM to determine the following

  1. The A/C high side pressure
  2. An A/C system load on the engine
  3. An immoderate A/C high side pressure
  4. The heat load at the A/C condenser

The air streams into the passenger compartment through the heater core and the evaporator core. The air temperature actuator drives the mixed air flap to induce the airflow. If the interior temperature should be increased, the mixed air flap is put into the position in which more air streams through the heater core. If the interior temperature should be decreased, the mixed air flap is put into the position in which more air streams through the evaporator core.

Recirculation Operation

The recirculation switch is integrated into the Radio/HVAC control. The selected recirculation switch position is sent to the HVAC control module via LIN-Bus. The HVAC control module controls the air intake through the air inlet actuator and recirculation actuator. In the recirculation mode the air inlet flap closes and the recirculation flap opens in order to circulate the air within the vehicle. In fresh air mode the air inlet flap opens and the recirculation flap is closed again in order to route outside air into the vehicle. Recirculation is only available if the defrost mode is not active. When the defrost mode is active, the recirculation actuator opens the recirculation flap and the air inlet actuator opens the air inlet flap and outside air is circulated to the windshield to reduce fogging.

In automatic mode the values of the windshield temperature and inside moisture sensor are used as control inputs for the HVAC control module application to calculate the fog risk on passenger compartment side of the windshield compartment side. The A/C compressor and the defrost mode are activated to prevent or remove fog on the passenger compartment side of the windshield.

Automatic Operation

In automatic operation, the HVAC control module maintains the comfort level inside of the vehicle by controlling the A/C compressor clutch, the blower motor, the air temperature actuators, mode actuator and recirculation actuator.

To put the HVAC system in automatic mode, the following is required

  1. The auto switch must be activated.
  2. The air temperature switches must be in any other position than full hot or full cold position.

Once the desired temperature is reached, the blower motor, mode, recirculation and temperature actuators automatically adjust to maintain the temperature selected. The HVAC control module performs the following functions to maintain the desired air temperature

  1. Monitors the following sensors: Ambient air temperature sensor Lower left air temperature sensor Lower right air temperature sensor Lower rear air temperature sensor (only CJ4) Upper left air temperature sensor Upper right air temperature sensor Upper rear air temperature sensor (only CJ4) Windshield temperature and inside moisture sensor Ambient light/sunload sensor
  2. Regulate the blower motor speed
  3. Regulate the rear blower motor speed (only CJ4)
  4. Position the air temperature actuators
  5. Position the rear air temperature actuators (only CJ4)
  6. Position the mode door actuator
  7. Position the rear mode door actuator (only CJ4)
  8. Position the recirculation actuator
  9. Position the air inlet actuator
  10. Request A/C operation
  11. Control of the A/C compressor

When the warmest position is selected in automatic operation the blower speed will increase gradually until the vehicle reaches normal operating temperature. When normal operating temperature is reached the blower stays on high speed and the air temperature actuators stays in the full heat position.

When the coldest position is selected in automatic operation the blower stays on high and the air temperature actuators stay in full cold position. The mode actuator remains in the panel position and the recirculation actuator will remain in the recirculation position.

Under cold ambient temperatures, the automatic HVAC system provides heat in the most efficient manner. The operator can select an extreme temperature setting but the system will not warm the vehicle any faster. Under warm ambient temperatures, the automatic HVAC system also provides air conditioning in the most efficient manner. Selecting an extreme cool temperature will not cool the vehicle any faster.

In automatic mode the values of the windshield temperature and inside moisture sensor are used as control inputs for the HVAC control module application to calculate the fog risk on the passenger compartment side of the windshield and ability to reduce fuel consumption by decreasing A/C compressor power to a minimum without causing any fog. The A/C compressor and the defrost mode are activated to prevent or remove fog on the passenger compartment side of the windshield. The sensor will also enable partial recirculation mode in order to improve heat-up performance of the passenger compartment under cold ambient temperature conditions without the risk of mist build-up on the windshield.

Engine Coolant

Engine coolant is the essential element of the heating system. The thermostat controls the normal engine operating coolant temperature. The thermostat also creates a restriction for the cooling system that promotes a positive coolant flow and helps prevent cavitation.

Coolant enters the heater core through the inlet heater hose, in a pressurized state. The heater core is located inside the HVAC control module. The ambient air drawn through the HVAC control module absorbs the heat of the coolant flowing through the heater core. Heated air is distributed to the passenger compartment, through the HVAC control module, for passenger comfort. Opening or closing the air temperature flap controls the amount of heat delivered to the passenger compartment. The coolant exits the heater core through the return heater hose and recirculates back to the engine cooling system.

A/C Cycle

Refrigerant is the key element in an air conditioning system. R-134a is presently the only Environmental Protection Agency 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 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 A/C refrigerant pressure sensor fails or if the refrigerant system becomes restricted and refrigerant pressure continued 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 tubing and aluminum cooling fins, which allows rapid heat transfer for the refrigerant. The semi-cooled liquid refrigerant exits the condenser and flows to the Receiver/Dehydrator(R/D).

The R/D contains desiccant that absorbs moisture that may be in the refrigerant system. The R/D also acts as a storage vessel to ensure that a steady flow of liquid reaches the thermal expansion valve. The refrigerant exits the R/D and flows through the liquid line to the thermal expansion valve.

The thermal expansion valve is located at the front of dash and attaches to the evaporator inlet and outlet pipes. 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 on the refrigerant is lowered. 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 control 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 through the suction line and back to the A/C compressor, in a vapor state, and completing the A/C cycle of heat removal. At the A/C compressor, the refrigerant is compressed again and the cycle of heat removal is repeated.

The conditioned air is distributed through the HVAC control 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 control module as water.

See also:
• Radio Control Assembly Replacement
• Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement
• Diagnostic System Check - Vehicle
• Strategy Based Diagnosis
• Diagnostic Procedure Instructions
• Symptom Byte List
• COMPONENT CONNECTOR END VIEWS - INDEX
• Circuit Testing
• Connector Repairs
• Testing for Intermittent Conditions and Poor Connections
• Wiring Repairs
• Control Module References
• Diagnostic Repair Verification
• Power Mode Mismatch
• Steering Wheel Controls Description and Operation
• Checking Aftermarket Accessories
• Heating Performance Diagnostic
• Instrument Panel Compartment Replacement
• Fastener Caution
• Battery Negative Cable Disconnection and Connection
• Air Inlet Grille Panel Replacement
• Inside Rearview Mirror Replacement
• Ambient Air Quality Sensor Replacement
• Automatic HVAC Description and Operation
• Low Reference Test
• HVAC Component Replacement Reference

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