MODEL IDENTIFICATION
| Body Designation | Model |
|---|---|
| "A" Body | Century, Cutlass Ciera & Cutlass Cruiser |
| (1) Body codes are determined by fourth character of VIN code. | |
| (1) | Body codes are determined by fourth character of VIN code. |
BODY CODE DESIGNATIONS (1)
DESCRIPTION & OPERATION
To improve idle quality and Wide Open Throttle (WOT) performance, and for system protection, the A/C compressor clutch is controlled by the Powertrain Control Module (PCM).
A refrigerant pressure sensor is used to indicate high and low side refrigerant pressure to the PCM for controlling cooling fan, A/C compressor clutch and Idle Air Control (IAC) valve. If a fault is detected in refrigerant pressure circuit, A/C compressor clutch will be disabled.
The A/C compressor clutch relay is controlled by the PCM. This allows the PCM to raise idle speed before engaging compressor clutch, and disable compressor clutch during WOT, high engine RPM, high power steering loads and hot engine restarts. PCM also disables compressor clutch if coolant temperature becomes excessive.
TROUBLE SHOOTING
Note. This article contains test flocharts which are part of General Motors Computerized Engine Controls. Only those flocharts required to test A/C compressor clutch control are included. Other diagnostic information may be referenced while performing A/C compressor clutch control diagnosis. For complete information on General Motors Computerized Engine Control systems, see appropriate articles in ENGINE PERFORMANCE section.
Trouble shoot A/C compressor clutch control using appropriate schematic and diagnostic flocharts. See A/C COMPRESSOR CLUTCH RELAY LOCATION table for A/C compressor clutch relay location.
RELAY LOCATION
| Application | Location |
|---|---|
| "A" Body | (1) In Right Front Corner Of Engine Compartment |
| (1) see scheme 3 | |
| (1) | See scheme 3 |
A/C COMPRESSOR CLUTCH RELAY LOCATION
TROUBLE SHOOTING CHART DIRECTORY
| Application | Figure No. | |
|---|---|---|
| "A" Body | ||
| 2.2L VIN 4 | 1-4 | |
| 3.1L VIN M | 5-8 | |
A/C COMPRESSOR CLUTCH CHART INDEX
SCAN TESTER
A variety of information is transmitted through Data Link Connector (DLC) terminal "E" or "M", depending on engine. This data is transmitted at a high frequency which requires a Tech 1 scan tester for interpretation. Several scan testers are available for diagnostic work. Scan testers other than Tech 1 scan tester will function and provide information for diagnostic work; however, some flocharts will specify a Tech 1 scan tester. Failure to use a Tech 1 scan tester when specified may result in incorrect diagnosis of a system.
CHART C-10, A/C COMPRESSOR CLUTCH CKT DIAGNOSIS 2.2L (1 OF 2)
A/C compressor clutch relay is controlled by the Powertrain Control Module (PCM). The PCM provides a ground on circuit No. 459 and A/C is requested. PCM will delay A/C compressor clutch engagement momentarily after A/C is requested. This delay allows Idle Air Control (IAC) valve to adjust engine RPM for additional load.
PCM will temporarily disengage A/C compressor clutch for a precalibrated time during one or more of the following conditions: hot engine restart, Wide Open Throttle (WOT), engine RPM greater than 6000 RPM, engine coolant temperature is greater than 251°F (122°C), A/C refrigerant pressure less than 43 psi (3.0 kg/cm 2 ) or greater than 429 psi (30.2 kg/cm 2 ) and IAC reset. A/C compressor clutch will remain disengaged if Diagnostic Trouble Code (DTC) 66 is present, and no A/C request signal exists from A/C select switch or circuit.
Note. Test numbers refer to numbers on diagnostic flochart.
- If DTCs are present, see appropriate article in ENGINE PERFORMANCE section. PCM will energize A/C compressor clutch relay only when engine is running. This test will determine whether relay or circuit No. 459 is faulty.
- Determines if signal is reaching PCM through circuit No. 66 from A/C control panel. Signal should only be present when A/C mode or defrost mode is selected.
Diagnostic Aids
If complaint is insufficient cooling, problem may be caused by an inoperative cooling fan. See appropriate C-12 chart in ENGINE COOLING FANS article in the ENGINE COOLING section. If cooling fan operates correctly, problem is a basic A/C system problem.
PCM will disable A/C compressor if refrigerant pressure is not 43-429 psi (3.0-30.2 kg/cm 2 ). If refrigerant pressure is okay, check A/C pressure sensor circuit. If A/C pressure sensor circuit is okay, replace A/C pressure sensor.
Scheme 1
Scheme 2
CHART C-10, A/C COMPRESSOR CLUTCH CKT DIAGNOSIS 2.2L (2 OF 2)
Note. Test numbers refer to numbers on diagnostic flochart.
- Determines if A/C pressure sensor is out-of-range, causing A/C compressor to be disengaged.
- With engine off and field service mode activated, PCM should ground circuit No. 459, causing test light to come on.
If complaint is insufficient cooling, problem may be caused by an inoperative cooling fan. See appropriate C-12 chart in ENGINE COOLING FANS article in the ENGINE COOLING section. If cooling fan operates correctly, problem is a basic A/C system problem.
PCM will disable A/C compressor if refrigerant pressure is not 43-429 psi (3.0-30.2 kg/cm 2 ). If refrigerant pressure is okay, check A/C pressure sensor circuit. If A/C pressure sensor circuit is okay, replace A/C pressure sensor.
Scheme 3
CHART C-10, A/C COMPRESSOR CLUTCH CKT DIAGNOSIS 3.1L (1 OF 2)
A/C compressor clutch relay is controlled by the Powertrain Control Module (PCM). The PCM provides a ground on circuit No. 459 and A/C is requested. PCM will delay A/C compressor clutch engagement momentarily after A/C is requested. This delay allows Idle Air Control (IAC) valve to adjust engine RPM for additional load.
PCM will temporarily disengage A/C compressor clutch for a precalibrated time during one or more of the following conditions: engine not running, engine coolant temperature greater than 255°F (124°C), A/C refrigerant pressure less than -17 psi (-1.2 kg/cm 2 ) or greater than 457 psi (32 kg/cm 2 ) and IAC reset. A/C compressor clutch will remain disengaged if Diagnostic Trouble Code (DTC) P1530 is present, and no A/C request signal exists from A/C select switch or circuit.
Note. Test numbers refer to numbers on diagnostic flochart.
- If DTCs are present, see appropriate article in ENGINE PERFORMANCE section. PCM will energize A/C compressor clutch relay only when engine is running. This test will determine whether relay or circuit No. 459 is faulty.
- Determines if signal is reaching PCM through circuit No. 66 from A/C control panel. Signal should only be present when A/C mode or defrost mode is selected.
Check branch circuits and splices to other components. If complaint is insufficient cooling, problem may be caused by an inoperative cooling fan. See appropriate C-12 chart in ENGINE COOLING FANS article in the ENGINE COOLING section. If cooling fan operates correctly, problem is a basic A/C system problem.
PCM will disable A/C compressor if refrigerant pressure is not -17 - 457 psi (-1.2 - 32 kg/cm 2 ). If refrigerant pressure is okay, check A/C pressure sensor circuit. If A/C pressure sensor circuit is okay, replace A/C pressure sensor.
Scheme 4
Scheme 5
CHART C-10, A/C COMPRESSOR CLUTCH CKT DIAGNOSIS 3.1L (2 OF 2)
Note. Test numbers refer to numbers on diagnostic flochart.
- Determines if A/C pressure sensor is out-of-range, causing A/C compressor to be disengaged.
- With engine off and field service mode activated, PCM should ground circuit No. 459, causing test light to come on.
If complaint is insufficient cooling, problem may be caused by an inoperative cooling fan. See appropriate C-12 chart in ENGINE COOLING FANS article in the ENGINE COOLING section. If cooling fan operates correctly, problem is a basic A/C system problem.
PCM will disable A/C compressor if refrigerant pressure is not -17 - 457 psi (-1.2 - 32 kg/cm 2 ). If refrigerant pressure is okay, check A/C pressure sensor circuit. If A/C pressure sensor circuit is okay, replace A/C pressure sensor.
