GM Service Manual Online
For 1990-2009 cars only

Important: The following steps must be completed before using the symptom tables.

  1. Perform the Diagnostic System Check before using the Symptom Tables in order to verify that all of the following are true:
  2. • There are no DTCs set.
    • The control module(s) can communicate via the serial data link.
  3. Review the system operation in order to familiarize yourself with the system functions.
  4. •  Operating Modes
    •  Relays and Sensors Description
    •  HVAC Blower Controls Circuit Description
    •  HVAC Compressor Controls Circuit Description
    •  Temperature Control Motor Circuit Description
    •  Air Conditioning (A/C) System Description
    •  Heater System Description
    •  Air Distribution System Description
    • Control Assembly Description

Visual/Physical Inspection

    • Inspect for aftermarket devices which could affect the operation of the HVAC System. Refer to Checking Aftermarket Accessories in Wiring Systems.
    • Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.

Intermittent

Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections in Wiring Systems.

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom:

    •  HVAC Compressor Clutch Does Not Engage
    •  HVAC Compressor Clutch Does Not Disengage
    •  Blower Motor Inoperative at Any Speed
    •  Blower Motor Low Speed Inoperative
    •  Blower Motor Medium Speed Inoperative
    •  Blower Motor Medium Speed Inoperative
    •  Blower Motor Medium Speed Inoperative
    •  Blower Motor High Speed Inoperative
    •  Air Delivery Improper
    •  Temperature Control Inoperative
    •  Cooling Insufficient - Air Conditioning (A/C) System
    •  Heating Insufficient
    •  Noise Diagnosis - Blower Motor
    •  Noise Diagnosis - Air Conditioning (A/C) System
    •  Cold Drafts on Floor
    •  Odor Diagnosis