TROUBLE SHOOTING
Note. This article contains test flow charts which are part of General Motors Computerized Engine Controls. Only those flow 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 appropriate articles in ENGINE PERFORMANCE section.
TROUBLE SHOOTING CHART DIRECTORY
| Application | Figure No. | |
|---|---|---|
| "C" & "K" Series | ||
| 4.3L VIN Z | 1-2 | |
| 5.0L VIN H | 1-2 | |
| 5.7L VIN K | 1-2 | |
| 6.5L VIN F, P & S | 3 | |
| 7.4L VIN N | 1-2 | |
A/C COMPRESSOR CLUTCH CHART INDEX
A/C REQUEST SIGNAL CIRCUIT DIAGNOSIS (M/T)
Turning on A/C system supplies battery voltage to A/C compressor clutch and Engine Control Module (ECM) terminal B8 through circuit No. 59, increasing idle speed. ECM 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 ECM. If circuit No. 59 is okay, repair faulty ECM connection or replace faulty ECM.
A/C Request Signal Circuit Diagnostic Schematic (M/T). Scheme 1
A/C REQUEST SIGNAL CIRCUIT DIAGNOSIS (6.5L)
Turning on A/C system supplies battery voltage to A/C compressor clutch and Powertrain Control Module (PCM) terminal B4 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 or replace faulty PCM.
