GM Service Manual Online
For 1990-2009 cars only

Strategy Based Diagnostics

  1. Perform Diagnostic Starting Point - Engine Mechanicalbefore using the symptom tables, if applicable.
  2. Review the system operations in order to familiarize yourself with the system functions. Refer to Disassembled Views , Engine Component Description , Lubrication Description , and to the Drive Belt System 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 problem. The diagnostic flow is the place to start when repairs are necessary. For a detailed explanation, refer to Strategy Based Diagnosis .

Visual/Physical Inspection

    • Inspect for aftermarket devices which could affect the operation of the Engine. Refer to Checking Aftermarket Accessories .
    • Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.
    • Check for the correct oil level, proper oil viscosity, and correct 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:

    •  Base Engine Misfire without Internal Engine Noises
    •  Base Engine Misfire with Abnormal Internal Lower Engine Noises
    •  Base Engine Misfire with Abnormal Valve Train Noise
    •  Base Engine Misfire with Coolant Consumption
    •  Base Engine Misfire with Excessive Oil Consumption
    •  Engine Noise on Start-Up, but Only Lasting a Few Seconds
    •  Upper Engine Noise, Regardless of Engine Speed
    •  Lower Engine Noise, Regardless of Engine Speed
    •  Engine Noise Under Load
    •  Engine Compression Test
    •  Oil Consumption Diagnosis
    •  Oil Pressure Diagnosis and Testing
    •  Oil Leak Diagnosis
    •  Drive Belt Chirping, Squeal, and Whine Diagnosis
    •  Drive Belt Rumbling and Vibration Diagnosis
    •  Drive Belt Falls Off and Excessive Wear Diagnosis