Circuit Description
The PCM receives an A/C request signal from the A/C selector switch. When A/C is requested, the Powertrain Control Module (PCM) provides a ground path to the A/C clutch relay control circuit. When the relay circuit is grounded, the A/C compressor clutch relay is energized. The PCM delays grounding the relay circuit for 0.3 second, so the PCM can adjust the engine idle RPM 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, or TP sensor over 90 percent. |
| • | Engine RPM more than 6000 RPM. |
| • | During an Idle Air Control (IAC) valve reset. |
| The A/C compressor clutch relay will remain de-energized when one or both of the following conditions exist: |
| • | A DTC P0530 is set. |
| • | There is no A/C request signal to the PCM. |
| Refer to A/C diagnosis for more information on the A/C refrigerant systems. |
Diagnostic Aids
| • | If DTC P0530 is set, do not use this table. |
| • | An A/C refrigerant pressure outside the range of 43 to 428 psi, will cause the A/C compressor clutch to be disabled by the PCM. Observe the A/C refrigerant pressure parameter on the scan tool for 2 minutes with the engine idling and A/C ON. If pressure goes out of range, refer A/C Diagnosis. |
Test Description
The numbers below refer to numbers on the diagnostic table.
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The Powertrain OBD System Check prompts the technician to complete some basic checks and store the freeze frame and failure records data on the scan tool if applicable. This creates an electronic copy of the data taken when the malfunction occurred. The information is then stored on the scan tool for later reference.
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The PCM will only energize the A/C relay when the engine is running. This test will determine if the relay or control circuit is malfunctioning.
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By disconnecting the relay, the system can be divided into two sections. If the clutch does not disengage, the malfunction lies on the compressor side of the system.
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A test lamp that does not illuminate indicates that the A/C compressor clutch relay is malfunctioning.
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This step determines if the system is normal or if the A/C refrigerant pressure sensor reading is out of range.
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This step determines if the signal is reaching the PCM from the A/C control panel. The signal should only be present when an A/C mode or defrost mode has been selected.
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This step determines if the A/C refrigerant pressure sensor is out of range causing the A/C compressor clutch to be disabled or if the A/C charge is to low to allow A/C operation.
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Replacement PCMs must be programmed and the Crankshaft Position System Variation Learn Procedure must be performed. Refer to the latest Techline information for PCM programming.
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Connecting circuits 59 and 459 together bypasses the PCMs control of the A/C compressor clutch. An A/C compressor clutch that fails to engage at this point indicates that the malfunction is in circuit 59, the compressor coil or compressor coil ground circuit.
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With the engine running and the A/C relay commanded ON, the PCM should ground the A/C relay control circuit. This will also illuminate the test light.
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If no malfunctions have been found at this point, refer to Diagnostic Aids for additional checks and information.
Step | Action | Value(s) | Yes | No |
|---|---|---|---|---|
Did you perform the Powertrain On-Board Diagnostic (OBD) System Check? | -- | |||
2 |
Was DTC P0530 set? | -- | Go to DTC P0530 Air Conditioning (A/C) Refrigerant Pressure Sensor Circuit | |
Is the A/C compressor clutch engaged? | -- | |||
Disconnect the A/C relay. Does the A/C compressor clutch disengage? | -- | |||
5 |
Does the A/C compressor clutch cycle ON and OFF with the selector switch? | 85°C (185°F) | ||
With a test lamp connected to B+, probe the A/C relay control terminal. Does the test lamp illuminate? | -- | |||
7 | Disconnect the A/C clutch harness connector. Does the A/C compressor clutch disengage? | -- | ||
Are the high side pressures within the specified value of each other? | 20 psi | |||
Turn the A/C ON and OFF. Does the scan tool indicate when the A/C is requested and not requested correctly? | -- | |||
10 |
Was a repair necessary? | -- | ||
11 |
Was a repair necessary? | -- | ||
12 | Replace the A/C compressor clutch relay. Refer to Compressor Relay Replacement in HVAC System. Is the action complete? | -- | -- | |
13 | Replace the malfunctioning A/C compressor clutch assembly. Refer to Compressor Clutch Plate and Hub Assembly Removal (HT6/HD6) and Compressor Clutch Plate/Hub Assembly Install (HT6/HD6) in HVAC System. Is the action complete? | -- | -- | |
14 |
Does the DMM read the specified value? | B+ | ||
15 | Turn ON the ignition leaving the engine OFF. Is the A/C High side value between the specified values? | 40-430 psi | ||
16 |
Does the test lamp turn ON and OFF when the A/C selector switch is cycled? | -- | ||
17 |
Was a repair necessary? | -- | ||
18 | Replace the A/C refrigerant pressure sensor. Refer to Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement in HVAC System. Is the action complete? | -- | -- | |
19 | Repair the open or poor connection in the A/C refrigerant pressure sensor ground. Refer to Wiring Repairs or Connector Repairs in Wiring Systems. Is the action complete? | -- | -- | |
20 |
Does the test lamp illuminate on both circuits? | -- | ||
Are the high side pressure within the specified value of each other? | 20 psi | Go to Refrigerant System Checks | ||
|
Important:: The replacement PCM must be programmed. Refer to Powertrain Control Module Replacement/Programming . Replace the PCM. Is the action complete? | -- | -- | ||
23 | Repair the signal from the A/C selector switch Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
Connect a jumper between the A/C relay ignition positive voltage terminal and the A/C compressor clutch positive voltage terminal. Does the A/C compressor clutch engage? | -- | |||
25 | If the test lamp did not illuminate on the A/C relay battery positive voltage terminal, check for a short to ground in the A/C compressor clutch ignition positive voltage circuit or for a malfunctioning A/C compressor clutch diode and repair as necessary. Refer to Wiring Repairs in Wiring Systems. Was a repair necessary? | -- | ||
Does the test lamp illuminate? | -- | |||
27 |
Does the test lamp illuminate? | -- | ||
28 | Repair the open battery or ignition positive voltage circuit to the A/C relay. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
29 | Connect the test lamp to ground and again probe the compressor clutch relay control terminal. Did the test lamp illuminate? | -- | ||
30 | With a test lamp connected to B+, probe the A/C compressor clutch ground circuit. Does the test lamp illuminate? | -- | ||
31 | Repair the open in the A/C compressor clutch ignition positive voltage circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
32 |
Was a repair necessary? | -- | ||
33 |
Was a repair necessary? | -- | ||
34 | Replace the A/C compressor clutch coil. Refer to Compressor Clutch Coil Removal (HT6/HD6) and Compressor Clutch Coil Install (HT6/HD6) in HVAC System. Is the action complete? | -- | -- | |
35 | Repair the open or poor connection in the A/C compressor clutch ground circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |
Does the A/C compressor clutch cycle ON and OFF? | System OK |
