TROUBLE SHOOTING
Note. This article contains test charts which are part of General Motors Computerized Engine Controls. Only those charts 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 the G-TESTS W/CODES article in the ENGINE PERFORMANCE section.
Trouble shoot A/C compressor clutch control using appropriate schematic and diagnostic charts. See TROUBLE SHOOTING CHART DIRECTORY.
TROUBLE SHOOTING CHART DIRECTORY
| Application | See Figure |
|---|---|
| 4.3L VIN Z | (Scheme 1) |
| 5.0L VIN H | (Scheme 1) |
| 5.7L VIN K | (Scheme 1) |
| 6.5L VIN F, P & S | (Scheme 2) |
| 7.4L VIN N | (Scheme 1) |
A/C COMPRESSOR CLUTCH CHART INDEX
A/C REQUEST SIGNAL CIRCUIT DIAGNOSIS 4.3L - VIN W & Z, 5.0L - VIN H, 5.7L - VIN K, 7.4L - VIN N
Turning on A/C system supplies battery voltage to A/C compressor clutch and Powertrain Control Module (PCM) terminal E12 through circuit No. 59, increasing idle speed. PCM does not control A/C compressor clutch. If A/C compressor clutch is malfunctioning, repair basic A/C system problem. If A/C system is operating properly and idle speed drops too low when A/C compressor turns on or flares too high when A/C compressor turns off, check for an open circuit No. 59 to PCM. If circuit No. 59 is okay, repair faulty PCM connection (terminal E12) or replace faulty PCM.
Scheme 1
A/C REQUEST SIGNAL CIRCUIT DIAGNOSIS 6.5L - VIN F, P & S
Turning on A/C system supplies battery voltage to A/C compressor clutch and Powertrain Control Module (PCM) terminal PB4 through circuit No. 59, increasing idle speed. PCM does not control A/C compressor clutch. If A/C compressor clutch is malfunctioning, repair basic A/C system problem. If A/C system is operating properly and idle speed drops too low when A/C compressor turns on or flares too high when A/C compressor turns off, check for an open circuit No. 59 to PCM. If circuit No. 59 is okay, repair faulty PCM connection (terminal PB4) or replace faulty PCM.
