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Makes 🢒 GMC_Truck 🢒 2001 🢒 Sonoma Pickup - 2WD 🢒 HVAC 🢒 HVAC Systems - Manual 🢒 HVAC Compressor Clutch Does Not Engage

HVAC Compressor Clutch Does Not Engage 2.2 L

Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

  1. The A/C compressor relay output is disabled if engine coolant temperature is above 121°C (250°F).

  1. Placing the mode switch in any position other than OFF, along with placing the air temperature control switch in a cold setting, activates A/C operation. For the purpose of this and future steps where A/C operation is necessary, bi-level mode is used for consistent testing.

    2.

  2. The HVAC control assembly is inoperative when the module does not respond to any operator control requests.

Step

Action

Value

Yes

No

Schematic Reference:

DEFINITION: The A/C compressor clutch will not engage when an A/C request has been made and a Powertrain DTC has not been set.

1

Did you review the HVAC operation and perform the necessary inspections?

--

Go to Step 2

Go to

2

  1. Install a scan tool.
  2. Start the engine.
  3. With a scan tool, observe the ECT parameter in the Powertrain data list.

Does the scan tool indicate that the ECT parameter is below 121°C (250°F)?

--

Go to Step 3

Go to

3

Important: For A/C compressor operation, ambient air temperature must be above 3°C (38°F).

  1. Start the engine.
  2. Place the blower motor switch in the maximum speed position.
  3. Place the mode switch in the bi-level position.
  4. Place the air temperature switch in the coldest position.

Does the A/C compressor clutch engage?

--

Go to in Wiring Systems

Go to Step 4

4
  1. Park the vehicle inside or in the shade.
  2. Open the windows in order to ventilate the interior of the vehicle.
  3. If the A/C system was operating, then allow the A/C system to equalize for approximately 2 minutes.
  4. Turn OFF the ignition.
  5. Install the ACR 2000.
  6. Record the ambient air temperature at the vehicle.
  7. Record readings of the low and high side STATIC pressures.
  8. Compare the pressure values with the specifications for the ambient air temperature. Refer to in Heating, Ventilation and Air Conditioning.

Are the pressure values within the specifications for the ambient air temperature, and within 103 kPa (15 psi) of each other?

--

Go to Step 5

Go to in Heating, Ventilation and Air Conditioning

5
  1. Turn ON the ignition, with the engine OFF.
  2. With a scan tool, observe the A/C High Side Pressure parameter in the powertrain data list.
  3. Compare the A/C high side pressure on the scan tool to the high side pressure on the ACR 2000.

Are the high side pressure values within 103 kPa (15 psi) of each other?

--

Go to Step 6

Go to Step 19

6

Is the HVAC control assembly inoperative?

--

Go to Step 18

Go to Step 7

7
  1. Start the engine.
  2. With a scan tool, observe the A/C Request Signal parameter in the powertrain Engine Data 2 list.
  3. Place the air temperature switch in the coldest position.
  4. Place the mode switch in bi-level position.

Does the scan tool indicate that the A/C Request Signal parameter is YES?

--

Go to Step 8

Go to Step 30

8

With a scan tool, observe the A/C High Side Pressure parameter in the powertrain data list.

Does the scan tool indicate that the A/C High Side Pressure parameter is within the specified range?

310-2930 kPa

(45-425 psi)

Go to Step 12

Go to Step 9

9
  1. Turn OFF the ignition.
  2. Disconnect the A/C refrigerant pressure sensor.
  3. Start the engine.
  4. With a scan tool, observe the A/C High Side Pressure parameter.

Does the scan tool indicate that the A/C High Side Pressure parameter is greater than the specified value?

2930 kPa

(425 psi)

Go to Step 10

Go to Step 23

10
  1. Turn OFF the ignition.
  2. Connect a 3-amp fused jumper wire between the signal circuit and the low reference circuit of the A/C refrigerant pressure sensor.
  3. Start the engine.
  4. With a scan tool, observe the A/C High Side Pressure parameter.

Does the scan tool indicate that the A/C High Side Pressure parameter is less than the specified value?

310 kPa

(45 psi)

Go to Step 11

Go to Step 24

11
  1. Turn OFF the ignition
  2. Disconnect the fused jumper wire.
  3. Connect a 3-amp fused jumper wire between the 5-volt reference circuit and the signal circuit of the A/C refrigerant pressure sensor.
  4. Start the engine.
  5. With a scan tool, observe the A/C High Side Pressure parameter.

Does the scan tool indicate that the A/C refrigerant pressure sensor parameter is greater than the specified value?

2930 kPa

(425 psi)

Go to Step 22

Go to Step 21

12

With a scan tool, command the A/C Relay ON and OFF.

Does the A/C compressor clutch relay turn ON and OFF with each command?

--

Go to Step 16

Go to Step 13

13
  1. Turn OFF the ignition.
  2. Disconnect the A/C compressor clutch relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the coil side voltage supply circuit of the A/C Relay with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

--

Go to Step 14

Go to Step 32

14
  1. Connect a test lamp between the control circuit of the A/C compressor clutch relay and the coil side voltage supply circuit of the A/C compressor clutch relay.
  2. With a scan tool, command the A/C compressor clutch relay ON and OFF.

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

--

Go to Step 33

Go to Step 15

15

Does the test lamp remain illuminated with each command?

--

Go to Step 27

Go to Step 26

16
  1. Turn OFF the ignition.
  2. Disconnect the A/C compressor clutch relay.
  3. Probe the switch side voltage supply circuit of the A/C compressor clutch relay with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

--

Go to Step 17

Go to Step 31

17

Connect a 10-amp fused jumper wire between the switch side voltage circuit of the A/C compressor clutch relay and the A/C compressor clutch supply voltage circuit of the A/C compressor clutch.

Does the A/C compressor clutch engage?

--

Go to Step 33

Go to Step 28

18

Test the ignition 3 voltage circuit of the HVAC control assembly for a short to ground, a high resistance, or an open. Refer to and in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 43

Go to Step 20

19

Test the ground circuit of the A/C pressure sensor for an open. Refer to and in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 43

Go to Step 34

20

Test the ground circuit of the HVAC control assembly for an open. Refer to and in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 43

Go to Step 36

21

Test the 5-volt reference circuit of the A/C refrigerant pressure sensor for a short to ground. Refer to and in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 43

Go to Step 37

22

Test the 5-volt reference circuit of the A/C refrigerant pressure sensor for a short to voltage, a high resistance, or an open. Refer to and in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 43

Go to Step 34

23

Test the signal circuit of the A/C refrigerant pressure sensor for a short to ground. Refer to and in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 43

Go to Step 37

24

Test the signal circuit of the A/C refrigerant pressure sensor for a short to voltage, a high resistance, or an open. Refer to and in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 43

Go to Step 25

25

Test the low reference circuit of the A/C refrigerant pressure sensor for a high resistance or an open. Refer to and in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 43

Go to Step 37

26

Test the control circuit of the A/C compressor clutch relay for an open. Refer to and in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 43

Go to Step 37

27

Test the control circuit of the A/C compressor clutch relay for a short to ground. Refer to and in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 43

Go to Step 37

28

Test the A/C compressor clutch supply voltage circuit of the A/C compressor clutch for a short to ground, a high resistance, or an open. Refer to and in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 43

Go to Step 29

29

Test the ground circuit of the A/C compressor clutch for a high resistance or an open. Refer to and in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 43

Go to Step 35

30
  1. Turn OFF the ignition.
  2. Test the A/C request signal circuit for a short to ground, a high resistance, or an open. Refer to and in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 43

Go to Step 37

31

Repair the switch side voltage supply circuit of the A/C compressor clutch relay. Refer to in Wiring Systems.

Did you complete the repair?

--

Go to Step 43

--

32

Repair the coil side voltage supply circuit of the A/C compressor clutch relay. Refer to in Wiring Systems.

Did you complete the repair?

--

Go to Step 43

--

33

Inspect for poor connections at the A/C compressor clutch relay. Refer to and in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 43

Go to Step 39

34

Inspect for poor connections at the harness connector of the A/C refrigerant pressure sensor. Refer to and in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 43

Go to Step 38

35

Inspect for poor connections at the harness connector of the A/C compressor clutch. Refer to and in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 43

Go to Step 40

36

Inspect for poor connections at the harness connector of the HVAC control assembly. Refer to and in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 43

Go to Step 41

37

Inspect for poor connections at the harness connector of the powertrain control module (PCM). Refer to and in Wiring Systems.

Did you find and correct the condition?

--

Go to Step 43

Go to Step 42

38

Replace the A/C refrigerant pressure sensor. Refer to in Heating, Ventilation and Air Conditioning.

Did you complete the replacement?

--

Go to Step 43

--

39

Replace the A/C compressor clutch relay. Refer to in Heating, Ventilation and Air Conditioning.

Did you complete the replacement?

--

Go to Step 43

--

40

Replace the A/C compressor clutch coil. Refer to and in Heating, Ventilation and Air Conditioning.

Did you complete the replacement?

--

Go to Step 43

--

41

Replace the HVAC control assembly. Refer to .

Did you complete the replacement?

--

Go to Step 43

--

42

Important:  Perform the programming procedure for the PCM.

Replace the PCM. Refer to in Engine Controls - 2.2L.

Did you complete the replacement?

--

Go to Step 43

--

43

Operate the system in order to verify the repair.

Did you correct the condition?

--

System OK

Go to Step 4

HVAC Compressor Clutch Does Not Engage 4.3 L

Test Description

The number(s) below refer to the step number(s) on the diagnostic table.

  1. The A/C compressor relay output is disabled if engine coolant temperature is above 121°C (250°F).

  1. Placing the mode switch in any position other than OFF, along with placing the air temperature control switch in a cold setting, activates A/C operation. For the purpose of this and future steps where A/C operation is necessary, bi-level mode is used for consistent testing.

    2.

  2. The HVAC control assembly is inoperative when the module does not respond to any operator control requests.

    3.

  3. Ensure to test both A/C request signal circuits of the A/C high pressure sensor for the listed conditions.

Step

Action

Yes

No

Schematic Reference:

DEFINITION: The A/C compressor clutch will not engage when an A/C request has been made and a Powertrain DTC has not been set.

1

Did you review the HVAC operation and perform the necessary inspections?

Go to Step 2

Go to

2

  1. Install a scan tool.
  2. Start the engine.
  3. With a scan tool, observe the ECT parameter in the Powertrain data list.

Does the scan tool indicate that the ECT parameter is below 121°C (250°F)?

Go to Step 3

Go to

3

Important: For A/C compressor operation, ambient air temperature must be above 3°C (38°F).

  1. Start the engine.
  2. Place the blower motor switch in the maximum speed position.
  3. Place the mode switch in bi-level position.
  4. Place the air temperature switch in the coldest position.

Does the A/C compressor clutch engage?

Go to in Wiring Systems

Go to Step 4

4
  1. Park the vehicle inside or in the shade.
  2. Open the windows in order to ventilate the interior of the vehicle.
  3. If the A/C system was operating, then allow the A/C system to equalize (about 2 minutes).
  4. Turn OFF the ignition.
  5. Install the ACR 2000.
  6. Record the ambient air temperature at the vehicle.
  7. Record readings of the low and high side STATIC pressures.

Are the side pressure values within the specifications for the ambient air temperature, and within 103 kPa (15 psi) of each other?

Go to Step 5

Go to in Heating, Ventilation and Air Conditioning

5

Is the HVAC control assembly inoperative?

Go to Step 18

Go to Step 6

6
  1. Start the engine.
  2. With a scan tool, observe the A/C Request Signal parameter in the powertrain Engine Data 2 list.
  3. Place the air temperature switch in the coldest position.
  4. Place the mode switch in bi-level position.

Does the scan tool indicate that the A/C Request Signal parameter is YES?

Go to Step 8

Go to Step 7

7
  1. Turn OFF the ignition.
  2. Disconnect the A/C high pressure switch.
  3. Connect a 3 amp fused jumper wire between the A/C request signal circuits at the A/C high pressure switch connector.
  4. Start the engine.
  5. With a scan tool, observe the A/C Request Signal parameter.
  6. Place the air temperature switch in the coldest position.
  7. Place the mode switch in the bi-level position.

Does the scan tool indicate that the A/C Request Signal parameter is YES?

Go to Step 31

Go to Step 24

8

Does the scan tool indicate the A/C Compressor Cycling Switch parameter is Normal?

Go to Step 10

Go to Step 9

9
  1. Turn OFF the ignition.
  2. Disconnect the A/C low pressure switch.
  3. Connect a 3-amp fused jumper wire between the A/C low pressure switch signal and ground circuits.
  4. Start the engine.
  5. With a scan tool, observe the A/C Compressor Cycling Switch parameter.

Does the scan tool indicate the A/C Compressor Cycling Switch parameter is Normal?

Go to Step 28

Go to Step 20

10

With a scan tool, command the A/C Relay ON and OFF.

Does the A/C compressor clutch relay turn ON and OFF with each command?

Go to Step 14

Go to Step 11

11
  1. Turn OFF the ignition.
  2. Disconnect the A/C compressor clutch relay.
  3. Turn ON the ignition, with the engine OFF.
  4. Probe the coil side voltage supply circuit of the A/C compressor clutch relay with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

Go to Step 12

Go to Step 26

12
  1. Connect a test lamp between the control circuit of the A/C compressor clutch relay and the coil side voltage supply circuit of the A/C compressor relay.
  2. With a scan tool, command the A/C compressor clutch relay ON and OFF.

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

Go to Step 27

Go to Step 13

13

Does the test lamp remain illuminated with each command?

Go to Step 17

Go to Step 16

14
  1. Turn OFF the ignition.
  2. Disconnect the A/C compressor clutch relay.
  3. Probe the switch side voltage supply circuit of the A/C compressor clutch relay with a test lamp that is connected to a good ground.

Does the test lamp illuminate?

Go to Step 15

Go to Step 25

15

Connect a 10-amp fused jumper wire between the switch side voltage circuit of the A/C compressor clutch relay and the A/C compressor clutch supply voltage circuit of the A/C compressor clutch.

Does the A/C compressor clutch engage?

Go to Step 27

Go to Step 22

16

Test the control circuit of the A/C compressor clutch relay for an open. Refer to and in Wiring Systems.

Did you find and correct the condition?

Go to Step 39

Go to Step 32

17

Test the control circuit of the A/C compressor clutch relay for a short to ground. Refer to and in Wiring Systems.

Did you find and correct the condition?

Go to Step 39

Go to Step 32

18

Test the ignition 3 voltage circuit of the HVAC control assembly for a short to ground, a high resistance, or an open. Refer to and in Wiring Systems.

Did you find and correct the condition?

Go to Step 39

Go to Step 19

19

Test the ground circuit of the HVAC control assembly for an open. Refer to and in Wiring Systems.

Did you find and correct the condition?

Go to Step 39

Go to Step 30

20

Test the A/C low pressure switch signal circuit for a high resistance or an open. Refer to and in Wiring Systems.

Did you find and correct the condition?

Go to Step 39

Go to Step 21

21

Test the ground circuit of the A/C low pressure switch for a high resistance or an open. Refer to and in Wiring Systems.

Did you find and correct the condition?

Go to Step 39

Go to Step 32

22

Test the A/C compressor clutch supply voltage circuit at the A/C compressor clutch for a short to ground, a high resistance, or an open. Refer to and in Wiring Systems.

Did you find and correct the condition?

Go to Step 39

Go to Step 23

23

Test the ground circuit of the A/C compressor clutch for a high resistance or an open. Refer to and in Wiring Systems.

Did you find and correct the condition?

Go to Step 39

Go to Step 29

24

  1. Turn OFF the ignition.
  2. Reconnect the A/C high pressure switch.
  3. Test both of the A/C request signal circuit for a short to ground, a high resistance, or an open. Refer to and in Wiring Systems.

Did you find and correct the condition?

Go to Step 39

Go to Step 32

25

Repair the switch side voltage supply circuit of the A/C compressor clutch relay. Refer to in Wiring Systems.

Did you complete the repair?

Go to Step 39

--

26

Repair the coil side voltage supply circuit of the A/C compressor clutch relay. Refer to in Wiring Systems.

Did you complete the repair?

Go to Step 39

--

27

Inspect for poor connections at the A/C compressor clutch relay. Refer to and in Wiring Systems.

Did you find and correct the condition?

Go to Step 39

Go to Step 33

28

Inspect for poor connections at the harness connector of the A/C low pressure switch. Refer to and in Wiring Systems.

Did you find and correct the condition?

Go to Step 39

Go to Step 34

29

Inspect for poor connections at the harness connector of the A/C compressor clutch. Refer to and in Wiring Systems.

Did you find and correct the condition?

Go to Step 39

Go to Step 36

30

Inspect for poor connections at the harness connector of the HVAC control assembly. Refer to and in Wiring Systems.

Did you find and correct the condition?

Go to Step 39

Go to Step 37

31

Inspect for poor connections at the harness connector of the A/C high pressure switch. Refer to and in Wiring Systems.

Did you find and correct the condition?

Go to Step 39

Go to Step 35

32

Inspect for poor connections at the harness connector of the powertrain control module (PCM). Refer to and in Wiring Systems.

Did you find and correct the condition?

Go to Step 39

Go to Step 38

33

Replace the A/C compressor clutch relay. Refer to in Heating, Ventilation and Air Conditioning.

Did you complete the replacement?

Go to Step 39

--

34

Replace the A/C low pressure switch. Refer to in Heating, Ventilation, and Air Conditioning.

Did you complete the replacement?

Go to Step 39

--

35

Replace the A/C high pressure switch. Refer to in Heating, Ventilation, and Air Conditioning.

Did you complete the replacement?

Go to Step 39

--

36

Replace the A/C compressor clutch coil. Refer to and in Heating, Ventilation, and Air Conditioning.

Did you complete the replacement?

Go to Step 39

--

37

Replace the HVAC control assembly. Refer to .

Did you complete the replacement?

Go to Step 39

--

38

Important:  Perform the programming procedure for the PCM.

Replace the PCM. Refer to in Engine Controls - 4.3L.

Did you complete the replacement?

Go to Step 39

--

39

Operate the system in order to verify the repair.

Did you correct the condition?

System OK

Go to Step 4