The numbers below refer to the step numbers on the diagnostic table.
The HVAC control module is inoperative when the module does not respond to any operator control requests.
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 perform the HVAC Diagnostic System Check? | Go to Step 2 | Go to |
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).
Does the A/C compressor operate? | Go to in Wiring Systems | Go to Step 4 |
4 |
Are the low and high side pressure values within the allowable limits for the recorded 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 |
Are the high side pressure values within 103 kPa (15 psi) of each other? | Go to Step 6 | Go to Step 21 |
Is the HVAC control module inoperative? | Go to Step 20 | Go to Step 7 | |
7 |
Does the scan tool indicate that the A/C Request Signal parameter is ON? | Go to Step 10 | Go to Step 8 |
8 | Does the A/C request indicator illuminate? | Go to Step 9 | Go to Step 34 |
9 |
Does the scan tool indicate that the A/C Request Signal parameter is ON? | Go to Step 30 | Go to Step 27 |
10 | With a scan tool, observe the A/C Compressor Cycling Switch parameter in the powertrain data list. Does the scan tool indicate the A/C Compressor Cycling Switch parameter is Normal? | Go to Step 12 | Go to Step 11 |
11 |
Does the scan tool indicate the A/C Compressor Cycling Switch parameter is Normal? | Go to Step 32 | Go to Step 23 |
12 | With a scan tool, command the A/C compressor clutch 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 |
Does the test lamp illuminate? | Go to Step 14 | Go to Step 29 |
14 |
Does the test lamp turn ON and OFF with each command? | Go to Step 31 | Go to Step 15 |
15 | Does the test lamp remain illuminated with each command? | Go to Step 19 | Go to Step 18 |
16 |
Does the test lamp illuminate? | Go to Step 17 | Go to Step 28 |
17 |
Does the A/C compressor clutch engage? | Go to Step 31 | Go to Step 25 |
18 | 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 42 | Go to Step 35 |
19 | 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 42 | Go to Step 35 |
20 | Test the ignition 3 voltage circuit of the HVAC control module 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 42 | Go to Step 22 |
21 | Test the ground circuit of the A/C high pressure sensor for an open. Refer to and in Wiring Systems. Did you find and correct the condition? | Go to Step 42 | Go to Step 30 |
22 | Test the ground circuit of the HVAC control module for an open. Refer to and in Wiring Systems. Did you find and correct the condition? | Go to Step 42 | Go to Step 34 |
23 | 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 42 | Go to Step 24 |
24 | 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 42 | Go to Step 35 |
25 | 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 42 | Go to Step 26 |
26 | 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 42 | Go to Step 33 |
Did you find and correct the condition? | Go to Step 42 | Go to Step 35 | |
28 | 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 42 | -- |
29 | 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 42 | -- |
30 | Inspect for poor connections at the harness connector of the A/C high pressure sensor. Refer to and in Wiring Systems. Did you find and correct the condition? | Go to Step 42 | Go to Step 36 |
31 | 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 42 | Go to Step 37 |
32 | 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 42 | Go to Step 38 |
33 | 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 42 | Go to Step 39 |
34 | Inspect for poor connections at the harness connector of the HVAC control module. Refer to and in Wiring Systems. Did you find and correct the condition? | Go to Step 42 | Go to Step 40 |
35 | 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 42 | Go to Step 41 |
36 | Replace the A/C high pressure switch. Refer to A/C High Pressure Switch Replacement in Heating, Ventilation and Air Conditioning. Did you complete the replacement? | Go to Step 42 | -- |
37 | Replace the A/C compressor clutch relay. Did you complete the replacement? | Go to Step 42 | -- |
38 | Replace the A/C low pressure switch. Refer to in Heating, Ventilation, and Air Conditioning. Did you complete the replacement? | Go to Step 42 | -- |
39 | Replace the A/C compressor clutch coil. Refer to and in Heating, Ventilation, and Air Conditioning. Did you complete the replacement? | Go to Step 42 | -- |
40 |
Important: Perform the recalibration procedure for the HVAC control module. Replace the HVAC control module. Refer to . Did you complete the replacement? | Go to Step 42 | -- |
41 |
Important: Perform the reprogramming procedure for the PCM. Replace the PCM. Refer to in Engine Controls - 4.3L. Did you complete the replacement? | Go to Step 42 | -- |
42 | Operate the system in order to verify the repair. Did you correct the condition? | System OK | Go to Step 4 |