Diagnosis
Refer to the Air Conditioning portion of the service manual for the diagnosis of the refrigerant portion of the system.
A scan tool can be used to display the following parameters:
| • | A/C Request--This displays if PCM has received an A/C request from Body Function Controller (BFC) YES or NO. |
| • | A/C Clutch--This displays if the PCM has commanded the A/C clutch ON or OFF. |
| • | A/C Highside--This displays the A/C refrigerant highside pressure in VOLTS andPSI . |
Circuit Description
The PCM receives an A/C request signal from the Body Fucntion Controller (BFC) over the Class ll 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 .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%). |
| • | Engine RPM greater 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 Air Conditioning System portion of the service manual for more information on the A/C refrigerant systems. |
Diagnostic Aids
| • | If DTCs P0530, P1601 or P1610 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 protion of the service manual. |
| • | If the fan operates correctly, refer to Air Conditioning System portion of the service manual for further diagnosis. |
| • | 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 toAir Conditioning System portion of the service manual for further diagnosis. |
Test Description
The number(s) below refer(s) to the number(s) on the diagnostic table.
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The Powertrain OBD System Check prompts you to complete some of the 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 captured when the malfunction occurred. The scan tool stores this data for later reference.
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The PCM will only energize the A/C relay when the engine is running or momentarily during cranking the engine in order to minimize the slugging noise. This step 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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This step determines if the signal is reaching the PCM from the A/C control panel from the Body Function Controller (BFC). The signal should only be present when an A/C mode or a defrost mode has been selected and the blower motor is turned ON.
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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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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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The A/C request signal is communicated through the BFC to the PCM over the Class ll serial data line. The BFC also receives other information in order to decide if the A/C request should be enabled. This step checks for the A/C request switch for the correct function. Additional steps must be completed in order to perform this step correctly. The blower motor must be turned ON and the heater, the vent, and the A/C Control assembly (HVAC) selector switch must not be in the OFF position. With the A/C selector switch in the OFF position, the scan tool should read A/C request OFF. If the A/C selector switch is in the ON position, the scan tool may read Clutch enabled or the following conditions: OFF, Low RPM, - OFF, Low Ambient - OFF, High Press - OFF, Low Battery Voltage - OFF, High Coolant Temp. If any of the above conditions are present on the scan tool when the A/C selector switch is enabled, the BFC senses a change.
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Connecting the ignition feed circuit and the A/C compressor Clutch feed circuit together bypasses the PCM's 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 the A/C Compressor Clutch feed circuit, the compressor coil, or the compressor coil ground circuit.
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Locate and repair any shorts that may have caused the fuse to open before replacement.
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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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Reprogram the replacement PCM and perform the crankshaft position system variation learning procedure. Refer to the latest Techline information for PCM programming and the Powertrain Control Module (PCM) for the crankshaft position system variation learning 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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If no malfunctions are present at this point, refer to the 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 | Install a scan tool. Were DTCs P0530, P1601 or P1610 set? | -- | Go to DTC tables first | |
Turn ON the ignition leaving the engine OFF. Is the A/C compressor clutch engaged? | -- | |||
Disconnect the A/C relay. Does the A/C compressor clutch disengage? | -- | |||
Does the scan tool indicate when the A/C is requested and not requested correctly? | -- | |||
Does the test light illuminate? | -- | |||
7 | Disconnect the A/C clutch electrical connector. Does the A/C compressor clutch disengage? | -- | ||
Check the A/C compressor clutch relay control circuit for a short to ground and repair the circuit as necessary. Was a repair necessary? | -- | |||
9 | Replace the A/C compressor clutch relay. Is the action complete? | -- | -- | |
10 | Repair the short to B+ in the A/C compressor clutch ignition feed circuit. Is the action complete? | -- | -- | |
11 | Replace the malfunctioning A/C compressor clutch assembly. Is the action complete? | -- | -- | |
Does the scan tool display indicate change when commanded? | -- | |||
13 |
Does the test light turn ON and OFF when the A/C selector switch is cycled? | -- | ||
14 | Refer to the Body Function Controller (BFC) portion of the service manual for further diagnosis. Is the action complete? | -- | -- | |
15 | Repair the signal from the A/C selector switch (refer to the Electrical Diagnosis of the Compressor Control portion of the service manual). Is the action complete? | -- | -- | |
16 | Cycle the A/C selector switch ON and OFF. Does the A/C clutch turn ON and OFF when commanded? | -- | ||
17 |
Does the test light illuminate on both circuits? | -- | ||
Connect a jumper between the A/C relay ignition feed terminal and the A/C compressor clutch feed terminal. Does the A/C compressor clutch engage? | -- | |||
Was a repair necessary? | -- | |||
Does the test light illuminate? | -- | |||
21 |
Does the test light illuminate? | -- | ||
22 | Repair the open ignition feed circuit to the A/C relay. Is the action complete? | -- | -- | |
23 |
Did the test light illuminate? | -- | ||
Does the test light illuminate? | -- | |||
25 | Repair the open in the A/C compressor clutch ignition feed circuit. Is the action complete? | -- | -- | |
26 | Check the A/C compressor clutch relay control circuit for a short to voltage and repair the circuit as necessary. Was a repair necessary? | -- | ||
27 | Check the A/C compressor clutch relay control circuit for an open or for a poor electrical connection and repair the circuit as necessary. Was a repair necessary? | -- | ||
28 | Repair the open or the poor electrical connection in the A/C compressor clutch ground circuit. Is the action complete? | -- | -- | |
29 | Turn ON the ignition leaving the engine OFF. Is the A/C High side value between the specified values? | 40-430 psi | ||
30 |
Does the test light illuminate? | -- | ||
31 |
Are the High side pressures within the specified value of each other? | 20 psi | Go to Air Conditioning System | |
32 | Check for a poor electrical connection. If the connection is OK, replace the A/C refrigerant pressure sensor. Is the action complete? | -- | -- | |
33 | Check for an open or for a poor electrical connection in the A/C refrigerant pressure sensor ground circuit and repair the connection as necessary. Was a repair necessary? | -- | -- | |
34 | Replace the PCM. Is the action complete? | -- | -- | |
35 | Turn ON the ignition leaving the engine OFF. Is the A/C High side value between the specified value? | 40-430 psi | Go to Body Function Controller Diagnosis | |
Are the High side pressures within the specified value of each other? | 20 psi | Go to Air Conditioning System | ||
37 | Disconnect the A/C refrigerant pressure sensor electrical connector. Does the scan tool read A/C High side value less than the specified value? | 1.0 V (421 psi) | ||
38 |
Does the DVM measure the specified value? | 5.0 V | ||
39 | Connect a jumper wire between the A/C refrigerant pressure sensor 5.0 volt reference and the signal circuit terminals. Does the scan tool read A/C High side value greater than the specified value? | 4.6 V (421 psi) | ||
40 | Check for an open or for a poor electrical connection in the 5.0 volt reference circuit and repair the circuit as necessary. Was a repair necessary? | -- | ||
41 | Check the A/C signal circuit for a short to voltage and repair the circuit as necessary. Was a repair necessary? | -- | ||
42 | Check the A/C refrigerant pressure sensor signal circuit for an open, or a short to ground, or for a poor electrical connection and repair the circuit as necessary. Was a repair necessary? | -- | ||
Does the A/C compressor clutch cycle ON and OFF? | -- | System OK Refer to Diagnostic Aids |
