Circuit Description
The Powretrain Control Module (PCM) receives an A/C request signal from the instrument panel cluster (IPC) over the UART serial data line. 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 (TP sensor over 90 percent) |
| • | Engine RPM greater than 6,000 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 DTCs P0530 or U1016 is set |
| • | There is no A/C request signal to the PCM |
| Refer to the Air Conditioning portion of the service manual for more information on the A/C refrigerant systems. |
Diagnostic Aids
| • | If DTCs P0530 or U1016 are set, do not use this table. |
| • | If the complaint is insufficient cooling, the problem may be caused by an inoperative cooling fan. Refer to Electric Cooling Fan Diagnosis. |
| • | If the fan operates correctly, refer to A/C Diagnosis in the Air Conditioning portion of the service manual. |
| • | 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 to the Air Conditioning portion of the service manual. |
Test Description
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 light that does not illuminate indicates that the A/C compressor clutch relay is malfunctioning.
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Determines if the system is normal or if the A/C refrigerant pressure sensor reading is out of range.
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Determines if the signal is reaching the PCM from the A/C control panel through the IPC. The signal should only be present when an A/C mode or defrost mode has been selected.
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The A/C request signal is communicated through the IPC to the PCM over the UART serial data line. The A/C selector switch must send a signal to the IPC before the IPC will send a signal to the PCM to turn ON the A/C compressor.
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Before replacing the PCM, check for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals, poor terminals to wiring connections or physical damaged to the wiring harness. The replacement PCMs must be reprogrammed and the crankshaft position system variation procedure must be preformed. Refer to PCM Replacement/Programming for the PCM reprogramming and CKP System Variation Learn Procedure for the crankshaft variation learn procedure.
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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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Connecting circuits 59 and 439 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 | ||||
|---|---|---|---|---|---|---|---|---|
Was the Powertrain On-Board Diagnostic (OBD) System Check performed? | -- | Go to Powertrain On Board Diagnostic (OBD) System Check for 2.4L or Powertrain On Board Diagnostic (OBD) System Check for 2.2L | ||||||
2 | Turn ON the ignition switch leaving the engine OFF. Install a scan tool. Were DTCs P0530 or U1016 set? | -- | Go to DTC tables first | |||||
Is the A/C compressor clutch engaged? | -- | |||||||
Remove the A/C relay. Refer to A/C Compressor and Cooling Fan Relays Replacement . Does the A/C compressor clutch disengage? | -- | |||||||
5 |
Does the A/C compressor clutch cycle ON and OFF when the selector switch is cycled? | 85°C (185°F) | ||||||
Does the test light illuminate? | -- | |||||||
7 | Disconnect the A/C clutch electrical connector. Does the A/C compressor clutch disengage? | -- | ||||||
Are the A/C High side pressures within the specified value of each other? | 20 psi | |||||||
Turn ON and OFF the A/C selector switch. Does the scan tool indicate when the A/C is requested and not requested correctly? | -- | |||||||
10 |
Was a repair necessary? | -- | ||||||
11 |
Is the action complete? | -- | -- | |||||
12 | Repair the short to B+ in the A/C compressor clutch ignition feed circuit. Refer to Wiring Repairs in Wiring Systems. Is the action complete? | -- | -- | |||||
13 | Replace the malfunctioning A/C compressor clutch assembly. Refer to Compressor Clutch Plate/Hub Assembly Install in HVAC Systems - Manual. Is the action complete? | -- | -- | |||||
14 |
Does the DMM read the specified value? | B+ | ||||||
15 | Turn OFF the engine leaving the ignition switch ON. Is the A/C High side value between the specified values? | 40-430 psi | ||||||
Does the test light turn ON and OFF when the A/C selector switch is cycled? | -- | |||||||
Is the action complete? | -- | -- | ||||||
18 | Replace the A/C refrigerant pressure sensor. Refer to Air Conditioning (A/C) Refrigerant Pressure Sensor Replacement in HVAC Systems. Is the action complete? | -- | -- | |||||
19 |
Is the action complete? | -- | -- | |||||
20 |
Does the test light illuminate on both circuits? | -- | ||||||
Are the A/C High side pressure within the specified value of each other? | 20 psi | Go to Functional Check in HVAC Systems - Manual | ||||||
22 | Replace the IPC. Refer to Instrument Cluster Replacement in Instrument Panel, Gages and Cluster. 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 fused jumper wire between the following circuits:
Does the A/C compressor clutch engage? | -- | |||||||
25 | If the test light did not illuminate on the A/C relay battery feed terminal, check for a short to ground in the following item(s):
Was a repair necessary? | -- | ||||||
Does the test light illuminate? | -- | |||||||
27 |
Does the test light illuminate? | -- | ||||||
28 |
Was a repair necessary? | -- | ||||||
29 |
Did the test light illuminate? | -- | ||||||
30 |
Does the test light illuminate? | -- | ||||||
31 |
Is the action complete? | -- | -- | |||||
32 |
Was a repair necessary? | -- | ||||||
33 |
Was a repair necessary? | -- | ||||||
34 |
Is the action complete? | -- | -- | |||||
35 |
Is the action complete? | -- | -- | |||||
Does the A/C compressor clutch cycle ON and OFF? | System OK |
