GM Service Manual Online
For 1990-2009 cars only

Diagnostic Category

Diagnostic Information

DEFINITION: The following table consists of seven diagnostic categories that are located in the left-hand column. Using this column, choose the appropriate category based on the operating conditions of the vehicle or transmission. After selecting a category, use the right-hand column to locate the specific symptom diagnostic information.

Fluid Diagnosis

This category contains the following topics:

    • Fluid condition - appearance, contaminants, smell, overheating
    • Line pressure - high or low
    • Fluid leaks
    • Refer to Transmission Fluid Check .
    • Refer to Line Pressure Check .
    • Refer to Fluid Leak Diagnosis .

Noise and Vibration Diagnosis

This category contains the following topics:

    • Ratcheting noise
    • Noise - drive gear, final drive, whine, growl, rattle, buzz, popping
    • Vibration
    • Refer to No Park or Ratcheting Noise in Park .

Range Performance Diagnosis

This category contains the following topics:

    • No Park
    • No Reverse
    • No Drive
    • No engine braking
    • No gear selection
    • Refer to No Park or Ratcheting Noise in Park .
    • Refer to No Reverse or Slips in Reverse
    • Refer to Unable to Run in All Ranges .
    • Refer to Shift Cable Replacement .

Shift Quality/Feel Diagnosis

This category contains the following topic:

Harsh shifts

Refer to Harsh Engagement into any Drive Range .

Shift Pattern

This category contains the following topics:

    • One forward gear only
    • Slipping
    • Refer to First Gear Only .
    • Refer to No 2-3 Shift or 2-3 Shift Slipping .
    • Refer to Slips in First Gear .
    • Refer to Slipping or Harsh 1-2 Shift .

Shift Speed Diagnosis

This category contains the following topic:

Inaccurate or inconsistent shift points

Refer to High or Low Shift Points .

Torque Converter Diagnosis

This category contains the following topic

Torque Converter Diagnosis

Refer to Flexplate/Torque Converter Vibration Test .

If no symptoms are found

    • Refer to Transmission Fluid Check .
    • Refer to Road Test .
    • Refer to Line Pressure Check .