GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 Cadillac 🢒 2001 🢒 Catera 🢒 HVAC 🢒 HVAC Systems - Automatic 🢒 Too Cold in Vehicle

Test Description

The numbers below refer to the step numbers on the diagnostic table.

  1. Tests for the proper operation of the circuit in the high voltage range. If the fuse in the jumper opens when you perform this test, the signal circuit is shorted to ground.

    2.

  2. The inside air temperature sensor is an integrated into the heater and A/C control.

    3.

  3. Tests to ensure that the heater and A/C control has the ability to command the LH temperature valve actuator.

    4.

  4. Tests for the proper operation of the circuit in the high voltage range when the actuator is at rest.

    5.

  5. Tests for the proper operation of the circuit in the high voltage range when the actuator is at rest.

    6.

  6. Ensures the heater and A/C control has the ability to control the LH temperature valve actuator.

    7.

  7. Ensures the heater and A/C control has the ability to control the LH temperature valve actuator.

    8.

  8. Ensures the heater and A/C control has the ability to control the LH temperature valve actuator. Test lamp will be illuminated when connection made. Test lamp should increase intensity when commanded.

    9.

  9. Ensures the heater and A/C control has the ability to control the LH temperature valve actuator. Test lamp will be illuminated when connection made. Test lamp should increase intensity when commanded.

    10.

  10. Tests to ensure that the heater and A/C control has the ability to command the RH temperature valve actuator.

    11.

  11. Tests for the proper operation of the circuit in the high voltage range when the actuator is at rest.

    12.

  12. Tests for the proper operation of the circuit in the high voltage range when the actuator is at rest.

    13.

  13. Ensures the heater and A/C control has the ability to control the RH temperature valve actuator.

    14.

  14. Ensures the heater and A/C control has the ability to control the RH temperature valve actuator.

    15.

  15. Ensures the heater and A/C control has the ability to control the RH temperature valve actuator. Test lamp will be illuminated when connection made. Test lamp should increase intensity when commanded.

    16.

  16. Ensures the heater and A/C control has the ability to control the RH temperature valve actuator. Test lamp will be illuminated when connection made. Test lamp should increase intensity when commanded.

Step

Action

Values

Yes

No

Schematic Reference: HVAC Schematics

DEFINITION: The temperature cannot be adjusted, or the heating is insufficient.

1

Did you perform the HVAC Diagnostic System Check?

--

Go to Step 2

Go to Diagnostic System Check - HVAC Systems - Automatic

2

Turn ON the ignition with the engine OFF.

Does the heater auxiliary water pump operate?

--

Go to Step 3

Go to Heater Water Auxiliary Pump Inoperative

3
  1. Turn ON the ignition, with the engine OFF.
  2. Place the mode switch in any position except OFF.
  3. Place the blower control in each speed position.

Does the blower motor operate correctly for each speed position?

--

Go to Step 4

Go to Blower Motor Inoperative

4

Does the blower motor provide sufficient air flow?

--

Go to Step 5

Go to Air Delivery Improper

5
  1. Start the engine.
  2. Place the mode switch in the vent position.
  3. Place the blower motor switch in the maximum speed position.
  4. Place the recirculation switch in the ON position.

Does the recirculation door operate properly?

--

Go to Step 6

Go to Air Recirculation Malfunction

6

Inspect the cooling system for the following conditions:

    • A low coolant level
    • A loose or worn accessory drive belt
    • A leaking radiator hose or heater hose
    • A kinked radiator hose or heater hose
    • A missing radiator cap pressure seal
    • A leaking radiator cap

Refer to Heating Performance Diagnostic in Heating, Ventilation and Air Conditioning.

Did you find and correct the condition?

--

Go to Step 20

Go to Step 7

7
  1. Start the engine.
  2. Turn OFF the heater and A/C controls.

Does the A/C compressor operate?

--

Go to HVAC Compressor Clutch Does Not Disengage

Go to Step 8

8
  1. Turn OFF the ignition.
  2. Disconnect the headlamp automatic control ambient light sensor.
  3. Turn ON the ignition, with the engine OFF.
  4. Measure the voltage at terminal 1 of the headlamp automatic control ambient light sensor to a good ground.

Does the voltage measure near specified value?

5 V

Go to Step 9

Go to Step 55

9

Measure the voltage at terminal 1 to terminal 4 of the headlamp automatic control ambient light sensor.

Does the voltage measure near specified value?

5 V

Go to Step 10

Go to Step 56

10

  1. Turn OFF the ignition.
  2. Connect a 3 amp fused jumper wire between the circuit FM60 of the headlamp automatic control ambient light sensor and the circuit X812 of the headlamp automatic control ambient light sensor.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the Solar Sen. Intensity parameter in the Heating and Air Conditioning Data List.

Does the scan tool indicate that the Solar Sen. Intensity parameter is less than the specified value?

5 V

Go to Step 57

Go to Step 11

11
  1. Turn OFF the ignition.
  2. Connect the headlamp automatic control ambient light sensor.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, observe the Solar Intensity parameter.
  5. Using the J 42220 Universal 12V Leak Detection Lamp, direct lamp at the headlamp automatic control ambient light sensor.
  6. Cover headlamp automatic control ambient light sensor to shield from lamp.

Does the Solar Intensity parameter change state?

--

Go to Step 12

Go to Step 62

12

With a scan tool, command the Heating Cutoff Valve Test ON and OFF.

Does the water cut-off vacuum solenoid valve turn ON and OFF with each command?

--

Go to Step 16

Go to Step 13

13
  1. Disconnect the electrical connector for the water cut-off vacuum solenoid valve.
  2. Measure the resistance of the water cut-off vacuum solenoid valve.

Does the resistance measure within the specified range?

35-40 ohms

Go to Step 14

Go to Step 63

14
  1. Connect a test lamp across circuits 920 and 939 at the water cut-off vacuum solenoid valve.
  2. With a scan tool, command the Heating Cutoff Valve Test ON and OFF.

Does the test lamp turn ON and OFF with each command?

--

Go to Step 63

Go to Step 15

15
  1. Connect a test lamp from circuit 920 of the water cut-off vacuum solenoid valve to B+ voltage.
  2. With a scan tool, command the Heating Cutoff Valve Test ON and OFF.

Does the test lamp turn ON and OFF with each command?

--

Go to Step 58

Go to Step 59

16
  1. Install a thermometer near the ambient air outside, LH air duct, and the RH air duct temperature sensor.
  2. With a scan tool observe the following parameters:
    3. • Outside Temperature
    • LH Air Out Temp Act.
    • RH Air Out Temp Act.

Does the scan tool indicate that the sensors temperatures are within the specifications at the thermometer temperatures?

-3 to 3°C

(-5 to 5°F)

Go to Step 20

Go to Step 17

17

Inspect the suspect temperature sensor for the following conditions:

    • An obstruction to the airflow
    • Damaged or missing seal to the sensor
    • Misaligned air ducts
    • Misaligned sensor

Did you find and correct the condition?

--

Go to Step 72

Go to Step 18

18
  1. Disconnect the suspect air temperature sensor.
  2. Measure the voltage from the 5 volt reference circuit to the sensor ground circuit of the suspect air temperature sensor.

Does the voltage measure near the specified value?

5 V

Go to Step 64

Go to Step 19

19

Measure the voltage from the 5 volt reference circuit of the suspect air temperature sensor to a good ground .

Does the voltage measure near the specified value?

5 V

Go to Step 60

Go to Step 61

20

  1. Install a thermometer near the inside air temperature sensor.
  2. With a scan tool, observe the Inside Air Temperature parameter.

Does the scan tool indicate that the inside air temperature sensor temperature are within the specifications at the thermometer temperature?

-3 to 3°C

(-5 to 5°F)

Go to Step 21

Go to Step 71

21

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, command the Left Air Mix Door Mot. ON and OFF.

Does the scan tool indicate that the Left Air Mix Door Mot. parameter goes inactive within 10 seconds when the door is commanded?

--

Go to Step 45

Go to Step 22

22
  1. Turn OFF the ignition.
  2. Disconnect the LH temperature valve actuator.
  3. Turn ON the ignition, with the engine OFF.
  4. Measure the B+ power supply voltage at the LH temperature valve actuator connector to a good ground.

Does the voltage measure near the specified value?

B+

Go to Step 23

Go to Step 47

23

Important: Ensure the connector for the LH temperature valve actuator is connected during this step to avoid misdiagnosis.

  1. Turn OFF the ignition.
  2. Connect LH temperature valve actuator.
  3. Turn ON the ignition, with the engine OFF.
  4. Measure voltage on terminals 3 and 6 at the LH temperature valve actuator to a good ground.

Does the voltage measure near the specified value?

0.5 V

Go to Step 24

Go to Step 48

24

Important: Ensure the connector for the LH temperature valve actuator is connected during this step to avoid misdiagnosis.

Measure voltage on terminals 1 and 4 at the LH temperature valve actuator.

Does the voltage measure near the specified value?

B+

Go to Step 25

Go to Step 49

25

  1. Turn OFF the ignition.
  2. Disconnect the LH temperature valve actuator.
  3. Connect test lamp from terminal 2 to terminal 1 of the LH temperature valve actuator.
  4. Turn ON the ignition, with the engine OFF.
  5. With a scan tool, command the Left Air Mix Door Mot. ON and OFF.

Does the test lamp illuminate with each command?

--

Go to Step 26

Go to Step 50

26

  1. Turn OFF the ignition.
  2. Connect test lamp from terminal 5 to terminal 4 of the LH temperature valve actuator.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, command the Left Air Mix Door Mot. ON and OFF.

Does the test lamp illuminate with each command?

--

Go to Step 27

Go to Step 51

27

  1. Turn OFF the ignition.
  2. Connect test lamp from terminal 2 to terminal 3 of the LH temperature valve actuator.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, command the Left Air Mix Door Mot. ON and OFF.

Does the test lamp dim when commanded?

--

Go to Step 28

Go to Step 52

28

  1. Turn OFF the ignition.
  2. Connect test lamp from terminal 5 to terminal 6 of the LH temperature valve actuator.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, command the Left Air Mix Door Mot. ON and OFF.

Does the test lamp dim when commanded?

--

Go to Step 29

Go to Step 53

29
  1. Disconnect the LH temperature valve actuator.
  2. Measure the resistance from terminal 2 to terminal 1 of the LH temperature valve actuator.

Does the resistance measure near specified value?

90 ohms

Go to Step 30

Go to Step 65

30

Measure the resistance from terminal 2 to terminal 3 of the LH temperature valve actuator.

Does the resistance measure near specified value?

90 ohms

Go to Step 31

Go to Step 65

31

Measure the resistance from terminal 5 to terminal 4 of the LH temperature valve actuator.

Does the resistance measure near specified value?

90 ohms

Go to Step 32

Go to Step 65

32

Measure the resistance from terminal 5 to terminal 6 of the LH temperature valve actuator.

Does the resistance measure near specified value?

90 ohms

Go to Step 33

Go to Step 65

33

  1. Install a scan tool.
  2. Turn ON the ignition, with the engine OFF.
  3. With a scan tool, command the Right Air Mix Door Mot. ON and OFF.

Does the scan tool indicate that the Right Air Mix Door Mot. parameter goes inactive within 10 seconds when the door is commanded?

--

Go to Step 45

Go to Step 34

34
  1. Turn OFF the ignition.
  2. Disconnect the RH temperature valve actuator.
  3. Turn ON the ignition, with the engine OFF.
  4. Measure the B+ power supply voltage at the RH temperature valve actuator connector to a good ground.

Does the voltage measure near the specified value?

B+

Go to Step 35

Go to Step 47

35

Important: Ensure the connector for the RH temperature valve actuator is connected during this step to avoid misdiagnosis.

  1. Turn OFF the ignition.
  2. Connect RH temperature valve actuator.
  3. Turn ON the ignition, with the engine OFF.
  4. Measure voltage on terminals 3 and 6 at the RH temperature valve actuator to a good ground.

Does the voltage measure near the specified value?

0.5 V

Go to Step 36

Go to Step 48

36

Important: Ensure the connector for the RH temperature valve actuator is connected during this step to avoid misdiagnosis.

Measure voltage on terminals 1 and 4 at the RH temperature valve actuator.

Does the voltage measure near the specified value?

B+

Go to Step 37

Go to Step 49

37

  1. Turn OFF the ignition.
  2. Disconnect the RH temperature valve actuator.
  3. Connect test lamp from terminal 2 to terminal 1 of the RH temperature valve actuator.
  4. Turn ON the ignition, with the engine OFF.
  5. With a scan tool, command the Right Air Mix Door Mot. ON and OFF.

Does the test lamp illuminate with each command?

--

Go to Step 38

Go to Step 50

38

  1. Turn OFF the ignition.
  2. Connect test lamp from terminal 5 to terminal 4 of the RH temperature valve actuator.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, command the Right Air Mix Door Mot. ON and OFF.

Does the test lamp illuminate with each command?

--

Go to Step 39

Go to Step 51

39

  1. Turn OFF the ignition.
  2. Connect test lamp from terminal 2 to terminal 3 of the RH temperature valve actuator.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, command the Right Air Mix Door Mot. ON and OFF.

Does the test lamp dim when commanded?

--

Go to Step 40

Go to Step 52

40

  1. Turn OFF the ignition.
  2. Connect test lamp from terminal 5 to terminal 6 of the RH temperature valve actuator.
  3. Turn ON the ignition, with the engine OFF.
  4. With a scan tool, command the Right Air Mix Door Mot. ON and OFF.

Does the test lamp dim when commanded?

--

Go to Step 41

Go to Step 53

41
  1. Disconnect the RH temperature valve actuator.
  2. Measure the resistance from terminal 2 to terminal 1 of the RH temperature valve actuator.

Does the resistance measure near specified value?

90 ohms

Go to Step 42

Go to Step 65

42

Measure the resistance from terminal 2 to terminal 3 of the RH temperature valve actuator.

Does the resistance measure near specified value?

90 ohms

Go to Step 43

Go to Step 65

43

Measure the resistance from terminal 5 to terminal 4 of the RH temperature valve actuator.

Does the resistance measure near specified value?

90 ohms

Go to Step 44

Go to Step 65

44

Measure the resistance from terminal 5 to terminal 6 of the RH temperature valve actuator.

Does the resistance measure near specified value?

90 ohms

System OK

Go to Step 65

45
  1. Turn OFF the ignition.
  2. Disconnect the heater and A/C control connector C1.
  3. Turn ON the ignition, with the engine OFF.
  4. Measure the voltage on the ignition positive voltage circuit at the heater and A/C control connector.

Does the voltage measure near specified value?

B+

Go to Step 46

Go to Step 54

46

Test the ground circuit of the heater and A/C control for a high resistance or an open. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 72

Go to Step 66

47

Test the B+ power supply circuits of the applicable temperature valve actuator for an open, high resistance or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 72

Go to Step 66

48

Test the circuits in terminals 3 and 6 of the applicable temperature valve actuator for an open, high resistance or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 72

Go to Step 66

49

Test the circuits in terminals 1 and 4 of the applicable temperature valve actuator for an open, high resistance or short to ground. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 72

Go to Step 66

50

Test the circuit in terminal 1 of the applicable temperature valve actuator for an open, high resistance or short to power. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 72

Go to Step 66

51

Test the circuit in terminal 4 of the applicable temperature valve actuator for an open, high resistance or short to power. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 72

Go to Step 66

52

Test the circuit in terminal 3 of the applicable temperature valve actuator for an open, high resistance or short to power. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 72

Go to Step 66

53

Test the circuit in terminal 6 of the applicable temperature valve actuator for an open, high resistance or short to power. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 72

Go to Step 66

54

Repair the ignition positive voltage circuit to the heater and A/C control. Refer to Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 72

--

55

Test the 5 volt reference circuit of the headlamp automatic control ambient light sensor for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 72

Go to Step 66

56

Test the sensor ground circuit of the headlamp automatic control ambient light sensor for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 72

Go to Step 66

57

Test the sun sensor input circuit of the headlamp automatic control ambient light sensor for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 72

Go to Step 66

58

Test the circuit 939 of the water cut-off vacuum solenoid for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 72

Go to Step 66

59

Test the circuit 920 of the water cut-off vacuum solenoid for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 72

Go to Step 66

60

Test the sensor ground circuit of the suspect air temperature sensor for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 72

Go to Step 66

61

Test the 5 volt reference circuit of the suspect air temperature sensor for an open or high resistance. Refer to Circuit Testing and Wiring Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 72

Go to Step 66

62

Inspect for poor connections at the harness connector of the headlamp automatic control ambient light sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 72

Go to Step 67

63

Inspect for poor connections at the harness connector of the water cut-off vacuum solenoid valve. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 72

Go to Step 68

64

Inspect for poor connections at the harness connector of the suspect air temperature sensor. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 72

Go to Step 69

65

Inspect for poor connections at the harness connector of the applicable temperature valve actuator. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 72

Go to Step 70

66

Inspect for poor connections at the harness connector of the heater and A/C control. Refer to Testing for Intermittent Conditions and Poor Connections and Connector Repairs in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 72

Go to Step 71

67

Replace the headlamp automatic control ambient light sensor. Refer to Sun Load Sensor Replacement .

Did you complete the replacement?

--

Go to Step 72

--

68

Replace the water cut-off vacuum solenoid valve. Refer to Vacuum Electrical Solenoid Replacement - Hot Water Bypass Control .

Did you complete the replacement?

--

Go to Step 72

--

69

Replace the suspect air temperature sensor. Refer to Air Temperature Actuator Replacement - Right Side or Air Temperature Actuator Replacement - Left Side .

Did you complete the replacement?

--

Go to Step 72

--

70

Replace the suspect air temperature sensor. Refer to the applicable replacement procedure:

Did you complete the replacement?

--

Go to Step 72

--

71

Replace the heater and A/C controls. Refer to HVAC Control Module Replacement .

Did you complete the replacement?

--

Go to Step 72

--

72

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 2