Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSOLDSMOBILE1998EIGHTY-EIGHT V6-3.8L VIN KREPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTCOMPUTERS AND CONTROL SYSTEMSA/C SIGNALDESCRIPTION AND OPERATIONPCM CONTROLLED A/C
1998 Oldsmobile Eighty-Eight V6-3.8L VIN K
PCM Controlled A/C
1998 Oldsmobile Eighty-Eight V6-3.8L VIN KSECTION PCM Controlled A/C
DESCRIPTION
The air conditioning system uses a compressor with variable displacement. This compressor is referred to as the V-5 type compressor. The V-5 compressor meets A/C requirements without cycling.
OPERATION
The A/C compressor operation is controlled by the Powertrain Control Module (PCM) for the following reasons:
^ Improved idle quality during compressor clutch engagement.
^ Improved wide open throttle performance (WOT).
^ Protects the A/C compressor from operation with incorrect refrigerant pressures.
The A/C clutch electrical system consists of the following components:
^ The A/C control head and/or the A/C programmer.
^ The A/C refrigerant pressure sensor.
^ The A/C compressor clutch.
^ The A/C compressor clutch relay.
^ The PCM.
When an A/C mode is selected at the A/C control head, the A/C programmer provides a 12 volt signal to the A/C request circuit. The PCM monitors the A/C request circuit and controls the A/C compressor relay based on the A/C request signal. This allows the PCM to increase the engine idle speed just prior to A/C clutch engagement for better idle quality. In addition, the PCM will command the cooling fans ON during A/C operation. The PCM also monitors the A/C refrigerant pressure sensor circuit. If the A/C refrigerant pressure is too high or low, the PCM will disable The A/C compressor relay.
The PCM will enable the A/C compressor clutch whenever the engine is running and the A/C has been requested unless one or more of the following conditions are present:
^ Throttle angle is greater than 96%.
^ A/C head pressure is greater than 440 psi (4.6 volts) or less than 35 psi (0.4 volt) as determined by the A/C refrigerant pressure sensor.
^ Ignition voltage is less than 10.5 volts.
^ Engine speed is greater than 4400 RPM for any amount of time.
^ Engine speed is greater than 3700 RPM for longer than 5 seconds.
^ ECT is greater than 124°C (255°F).
^ Intake Air Temperature (IAT) is less than 5°C (41°F).
Any of the conditions described above will inhibit A/C compressor relay operation.
DIAGNOSTIC INFORMATION
DTC P0530, P0560, P1639, or P1654 can affect A/C operation. Refer to Testing and Inspection / Procedures / Diagnostic Tables if any DTCs are set.
The PCM Controlled Air Conditioning Diagnosis table should be used for diagnosing the electrical portion of the A/C compressor clutch circuit it a DTC is not set. To diagnose the refrigerant portion of the HVAC system, refer to the Heating and Air Conditioning. A scan tool will be used in diagnosing the system. The scan tool has the ability to display the A/C request and refrigerant pressure inputs to the PCM. The scan tool can display when the PCM has commanded the A/C clutch ON. The scan tool also has the ability to override the A/C request signal and energize the A/C control relay.
The air conditioning system uses a compressor with variable displacement. This compressor is referred to as the V-5 type compressor. The V-5 compressor meets A/C requirements without cycling.
OPERATION
The A/C compressor operation is controlled by the Powertrain Control Module (PCM) for the following reasons:
^ Improved idle quality during compressor clutch engagement.
^ Improved wide open throttle performance (WOT).
^ Protects the A/C compressor from operation with incorrect refrigerant pressures.
The A/C clutch electrical system consists of the following components:
^ The A/C control head and/or the A/C programmer.
^ The A/C refrigerant pressure sensor.
^ The A/C compressor clutch.
^ The A/C compressor clutch relay.
^ The PCM.
When an A/C mode is selected at the A/C control head, the A/C programmer provides a 12 volt signal to the A/C request circuit. The PCM monitors the A/C request circuit and controls the A/C compressor relay based on the A/C request signal. This allows the PCM to increase the engine idle speed just prior to A/C clutch engagement for better idle quality. In addition, the PCM will command the cooling fans ON during A/C operation. The PCM also monitors the A/C refrigerant pressure sensor circuit. If the A/C refrigerant pressure is too high or low, the PCM will disable The A/C compressor relay.
The PCM will enable the A/C compressor clutch whenever the engine is running and the A/C has been requested unless one or more of the following conditions are present:
^ Throttle angle is greater than 96%.
^ A/C head pressure is greater than 440 psi (4.6 volts) or less than 35 psi (0.4 volt) as determined by the A/C refrigerant pressure sensor.
^ Ignition voltage is less than 10.5 volts.
^ Engine speed is greater than 4400 RPM for any amount of time.
^ Engine speed is greater than 3700 RPM for longer than 5 seconds.
^ ECT is greater than 124°C (255°F).
^ Intake Air Temperature (IAT) is less than 5°C (41°F).
Any of the conditions described above will inhibit A/C compressor relay operation.
DIAGNOSTIC INFORMATION
DTC P0530, P0560, P1639, or P1654 can affect A/C operation. Refer to Testing and Inspection / Procedures / Diagnostic Tables if any DTCs are set.
The PCM Controlled Air Conditioning Diagnosis table should be used for diagnosing the electrical portion of the A/C compressor clutch circuit it a DTC is not set. To diagnose the refrigerant portion of the HVAC system, refer to the Heating and Air Conditioning. A scan tool will be used in diagnosing the system. The scan tool has the ability to display the A/C request and refrigerant pressure inputs to the PCM. The scan tool can display when the PCM has commanded the A/C clutch ON. The scan tool also has the ability to override the A/C request signal and energize the A/C control relay.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.