HVAC System - Automatic: Diagnosis Cadillac STS I

Scan Tool Output Controls

HVAC Control Module Scan Tool Output Controls

ECM Scan Tool Output Controls

Scan Tool Data List

HVAC Control Module Scan Tool Data List

ECM Scan Tool Data List

Circuit Description

The ambient air temperature sensor provides the HVAC control module software with the temperature of the air outside the vehicle. That temperature can be displayed in the driver information center (DIC). A reference voltage is supplied to the sensor thermistor and the HVAC control module determines the voltage drop across that device which is proportional to temperature. As the air temperature increases, the resistance decreases and the voltage signal decreases. As the air temperature decreases, the resistance increases and the voltage signal increases. The inside air temperature sensor provides the HVAC control module with the temperature of the air drawn through an aspirator from the passenger compartment across a sensor. A reference voltage is supplied to the sensor thermistor and the HVAC control module determines the voltage drop across that device which is proportional to temperature. As the air temperature increases, the resistance decreases and the voltage signal decreases. As the air temperature decreases, the resistance increases and the voltage signal increases.

DTC Descriptors

This diagnostic procedure supports the following DTCs

1. DTC B0158 Outside Air Temperature Sensor Circuit.
2. DTC B0163 Passenger Compartment Temperature Sensor Circuit.

This vehicle has DTCs which include DTC Symptoms. For more information on DTC Symptoms, refer to DTC Symptom Description in Vehicle DTC Information.

DTC B0158 or B0163

Conditions for Running the DTC

The ignition is turned ON.

Visual/Physical Inspection

1. Inspect for aftermarket devices which could affect the operation of the HVAC System. Refer to «Checking Aftermarket Accessories»(ref-197533-S03944243902005101200000) in Wiring Systems.
2. Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.
3. Verify the A/C compressor clutch turns freely and is not seized.
4. Verify that the customer is using the correct key to enable personalization and is not inadvertently activating auxiliary HVAC controls.
5. The A/C compressor will not operate in cold outside air temperatures. Refer to «Air Temperature Description and Operation»(ref-197560-S42300243782005101200000) .
6. The following conditions may cause window fogging: Wet carpet or mats High humidity Interior water leak Blocked A/C evaporator drain tube Maximum passenger capacity Blocked body pressure relief valves
7. Inspect the air distribution system for causes of reduced air flow: Obstructed or dirty passenger compartment air filter, if equipped Blocked or damaged air inlet or outlet vents

Symptom List

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

1. «HVAC Compressor Clutch Does Not Engage»(ref-197560-S19350007492005101200000)
2. «HVAC Compressor Clutch Does Not Disengage»(ref-197560-S08118794112005101200000)
3. «Blower Motor Always On»(ref-197560-S38781294002005101200000)
4. «Blower Motor Inoperative»(ref-197560-S28017168452005101200000)
5. «Blower Motor Malfunction»(ref-197560-S31004354172005101200000)
6. «Too Hot in Vehicle»(ref-197560-S29064761022005101200000)
7. «Too Cold in Vehicle»(ref-197560-S07414210622005101200000)
8. «Air Delivery Improper»(ref-197560-S00679745522005101200000)
9. «Air Recirculation Malfunction»(ref-197560-S04882761362005101200000)
10. «Leak Testing»(ref-197627-S14271993192005101200000) in Heating, Ventilation and Air Conditioning
11. «Noise Diagnosis - Blower Motor»(ref-197627-S15777028482005101200000) in Heating, Ventilation and Air Conditioning
12. «Noise Diagnosis - Air Conditioning (A/C) System»(ref-197627-S26229898672005101200000) in Heating, Ventilation and Air Conditioning
13. «Odor Diagnosis»(ref-197627-S40745734262005101200000) in Heating, Ventilation and Air Conditioning
14. «Steering Wheel Controls Inoperative»(ref-197539-S12953729862005101200000) in Entertainment

Scan Tool Not Completed

Refer to Air Quality Sensor (RPO K14) in the HVAC Systems Automatic Description and Operation to understand the functionality of this system. The air quality sensor sensitivity can be adjusted. Refer to Air Quality Calibration Offset .

Diagnostic Aids

1. The condition may be intermittent. Refer to «Testing for Intermittent Conditions and Poor Connections»(ref-197533-S35858719362005101200000) in Wiring Systems.
2. Inspect the air delivery system for the following conditions: A dirty HVAC air filter An obstruction to the airflow Air leaks Misaligned air ducts Broken or binding linkages or doors

Air Delivery Improper

1. If the control A circuit of the recirculation actuator is shorted to ground, the following conditions will occur. The recirculation actuator will operate properly when recirculation is requested. The recirculation actuator will continually modulate between the outside air and recirculation positions when outside air is requested.
2. If the control B circuit of the recirculation actuator is shorted to ground, the following conditions will occur. The recirculation actuator will operate properly when outside air is requested. The recirculation actuator will continually modulate between the outside air and recirculation positions when recirculation is requested.
3. The condition may be intermittent. Refer to «Testing for Intermittent Conditions and Poor Connections»(ref-197533-S35858719362005101200000) in Wiring Systems.
4. Inspect the recirculation door and the recirculation actuator for the following conditions: A misaligned recirculation actuator - Refer to «Recirculation Actuator Replacement»(ref-197560-S18564314042005101200000) . Broken or binding linkages A broken or binding recirculation door An obstruction that prevents the recirculation door from operating within its full range of motion Missing seals to the recirculation door Misaligned seals to the recirculation door

Air Recirculation Malfunction