GM Service Manual Online
For 1990-2009 cars only

Strategy Based Diagnostics

  1. Perform the Diagnostic System Check - Vehicle before using the symptom tables, if applicable.
  2. Review the system operations in order to familiarize yourself with the system functions. Refer to Disassembled Views and Engine Component Description.

All diagnosis on a vehicle should follow a logical process. Strategy based diagnostics is a uniform approach for repairing all systems. The diagnostic flow may always be used in order to resolve a system condition. The diagnostic flow is the place to start when repairs are necessary.

Visual/Physical Inspection

    • Inspect for aftermarket devices which could affect the operation of the engine.
    • Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.
    • Inspect the for the proper oil level, oil viscosity, and filter application.
    • Verify the exact operating conditions under which the concern exists. Note factors such as engine RPM, ambient temperature, engine temperature, amount of engine warm-up time, and other specifics.
    • Compare the engine sounds, if applicable, to a known good engine and make sure you are not trying to correct a normal condition.

Intermittent

Test the vehicle under the same conditions that the customer reported in order to verify the system is operating properly.

Symptom List

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

    •  Oil Pressure Diagnosis and Testing
    •  Oil Leak Diagnosis
    •  Engine Noise Diagnosis
    •  Engine Knocks Cold and Continues for Two-Three Minutes and/or Knock Increases with Engine Torque
    •  Engine Noise Under Load
    •  Light Knock Hot
    •  Engine Noise on Start-Up, but Only Lasting a Few Seconds
    •  Knocks at Idle Hot
    •  Main Bearing Noise
    •  Connecting Rod Bearing Noise
    •  Piston Noises
    •  Base Engine Misfire with Abnormal Valve Train Noise
    •  Engine Compression Test