A/C REQUEST SIGNAL CIRCUIT DIAGNOSIS 4.3L - VIN W & Z, 5.0L - VIN H ("G" Only), 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.

Fig 1: A/C Request Signal Circuit Diagnosis, Schematic (4.3L VIN W & Z, 5.0L VIN H, 5.7L VIN K & 7.4L VIN N "G" Series)

Courtesy of GENERAL MOTORS CORP.

Fig 2: A/C Request Signal Circuit Diagnosis, Schematic (4.3L VIN W & Z, 5.0L VIN H, 5.7L VIN K & 7.4L VIN N "P" Series)

Courtesy of GENERAL MOTORS CORP.