Refer to
A/C Relay and A/C Request Signal
.
Circuit Description
The PCM receives the A/C request from the A/C select switch. When the A/C is requested, the PCM will ground the A/C clutch relay control circuit. When the relay is grounded, the PCM energizes the A/C compressor clutch. The PCM delays grounding the relay circuit for 0.3 seconds so that the PCM can adjust the engine idle speed for the additional load
The PCM will temporarily de-energize the A/C compressor clutch relay for one or more of the following conditions:
| • | A hot engine restart |
| • | A wide open throttle |
| • | The engine speed is greater than 6000 RPM |
| • | An Idle Air Control (IAC) valve reset |
The A/C compressor clutch relay will remain de-energized when one of the following conditions exist:
| • | A DTC 530 is set. |
| • | There is no A/C request signal to the PCM. |
Refer to the A/C diagnostics in the HVAC section for additional information A/C refrigerant system.
Diagnostic Aids
| • | If the complaint is insufficient cooling, the problem could be an inoperative cooling fan. |
| • | An A/C refrigerant pressure outside of 43-468 PSI will cause the PCM to disable the A/C compressor clutch. |
| 1. | Observe the A/C refrigerant pressure parameter on the scan tool for 2 minutes with the engine idling and the A/C on. |
| 2. | Refer to the A/C diagnostics in the HVAC section if the A/C pressure goes out of range. |
| • | Inspect for a malfunctioning A/C compressor diode. |
Test Description
The numbers below refer to the step numbers on the Diagnostic Table.
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The Powertrain OBD System Check prompts the technician to complete some basic checks and to store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data the PCM recorded when the malfunction occurred. The scan tool then stores the information for later reference.
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If any one of these three fuses are open the A/C system will not operate.
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If the clutch does not disengage, the fault then lies on the compressor side of the circuit.
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A test light that does not illuminate indicates that the A/C relay is malfunctioning.
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This test will determine if the A/C refrigerant pressure sensor is out of range.
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This test will determine if the signal is reaching the PCM from the A/C selector switch. This signal should only be present when the A/C mode or defrost mode has been selected.
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When using the A/C gauges make sure that the gauges are reading accurately.
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Reprogram the replacement PCM. Refer to the latest Techline information for programming procedures.
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Inspect the complete circuit from the fuse to the component for a short to ground. Check the power feed circuit from the A/C compressor relay to the A/C compressor clutch.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to OBD System Check | ||
Check fuse #4 (Gauges), Fuse #6 (HTR A/C), and Fuse #14 (A/C Comp) for an open. Are all 3 fuses good? | -- | |||
Turn the ignition ON leaving the engine off. Is the A/C compressor clutch engaged? | -- | |||
4 | Disconnect the A/C relay. Did the A/C compressor clutch disengage? | -- | ||
5 |
Does the A/C compressor clutch cycle ON and OFF with the selector switch? | -- | ||
With a test lamp connected to B+, probe the A/C relay control terminal. Does the test lamp illuminate? | -- | |||
7 | Disconnect the A/C compressor clutch electrical connector. Does the A/C compressor clutch disengage? | -- | ||
Are the Highside pressures within the specified values of each other? | 20 psi | |||
Does the scan tool indicate when the A/C Request is ON and when the A/C Request is OFF? | -- | |||
10 |
Was a repair necessary? | -- | ||
11 | Replace the A/C compressor clutch relay. Refer to HVAC. Is the action complete? | -- | -- | |
12 | Repair the short to voltage in the A/C compressor clutch ignition feed circuit. Refer to Wiring Repairs in Engine Electrical. Is the action complete? | -- | -- | |
13 | Replace the A/C compressor clutch assembly. Refer to HVAC. Is the action complete? | -- | -- | |
14 |
Does the test lamp illuminate? | -- | ||
15 |
Is the A/C Highside pressure between the specified value? | 40-430 psi | ||
16 |
Does the test lamp turn ON when the selector switch is turned ON and turn OFF when the selector switch is turned OFF? | -- | ||
17 |
Was a repair necessary? | -- | ||
18 | Replace the A/C refrigerant pressure sensor. Refer to HVAC. Is the action complete? | -- | -- | |
19 | Repair the poor connection in the A/C refrigerant pressure sensor ground circuit. Refer to HVAC. Is the action complete? | -- | -- | |
20 |
Does the test lamp illuminate on both circuits? | -- | ||
Are the Highside pressures within the specified values of each other? | 20 psi | Go to HVAC | ||
Replace the PCM. Refer to Powertrain Control Module Replacement/Programming . Is the action complete? | -- | -- | ||
23 |
Was a repair necessary? | -- | ||
24 |
Does the A/C compressor clutch engage? | -- | ||
25 | Replace the A/C selector switch (HVAC blower). Refer to HVAC. Is the action complete? | -- | -- | |
26 |
Does the test lamp illuminate? | -- | ||
27 |
Does the test lamp illuminate? | -- | ||
28 | Repair the open in the power feed circuit to the A/C compressor clutch relay that did not illuminate the test lamp. Is the action complete? | -- | -- | |
29 |
Did the test lamp illuminate? | -- | ||
30 | With a test lamp connected to B+, probe the A/C compressor clutch ground circuit. Did the test lamp illuminate? | -- | ||
31 | Repair the open in the A/C compressor clutch ignition feed circuit. Is the action complete? | -- | -- | |
32 |
| -- | ||
33 | Inspect the A/C compressor clutch relay control circuit for an open or a poor connection. Is a repair necessary? | -- | ||
34 | Replace the A/C compressor clutch coil. Refer to HVAC. Is the action complete? | -- | -- | |
35 | Repair the open or the poor connection in the A/C compressor clutch ground circuit. Is the action complete? | -- | -- | |
Is the action complete? | -- | -- | ||
37 |
Does the A/C compressor clutch cycle ON and OFF? | -- | System OK Refer to Diagnostic Aids |
