GM Service Manual Online
For 1990-2009 cars only

Diagnostic Category

Diagnostic Information

DEFINITION: The following table consists of 8 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 specified symptom diagnostic information.

Electrical Diagnosis

    • A/T warning indicator always ON or flashes continuously
    • O/D OFF indicator always ON
    • O/D OFF indicator inoperative
    • Refer to overdrive OFF indicator, always ON
    • Refer to overdrive OFF indicator inoperative

Fluid Diagnosis

    • 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
    • Refer to Oil Out the Vent

Noise and Vibration Diagnosis

    • Noise - drive gear, final drive, whine, growl, rattle buzz, popping
    • Vibration

Refer to Noise and Vibration Analysis

Range Performance Diagnosis

    • No Park
    • No Reverse
    • No Drive
    • No Engine Braking
    • No Gear Selection
    • Refer to Unable to Run in All Ranges in All Ranges
    • Refer to First Gear Range Only - No Upshift
    • Refer to No Drive in Drive Range in Forward Ranges
    • Refer to No Reverse
    • Refer to Drives in Neutral in Neutral
    • Refer to No Engine Braking in First Gear in First Gear
    • Refer to Shift Cable Replacement

Shift Quality/Feel Diagnosis

Harsh shifts

Shift Pattern

    • One forward gear only
    • Slipping
    • Refer to Transmission Slips
    • Refer to Slips in Reverse
    • Refer to No 1-2 Upshift
    • Refer to No 2-3 Upshift
    • Refer to No 3-4 Upshift
    • Refer to Inaccurate Shift Points
    • Refer to Slipping 1-2 Upshift
    • Refer to Slipping 2-3 Upshift
    • Refer to Slipping 3-4 Upshift
    • Refer to Abrupt 1-2 Upshift
    • Refer to Abrupt 2-3 Upshift
    • Refer to Abrupt 3-4 Upshift
    • Refer to Lack of Power or Hesitation

Torque Converter Diagnosis

Torque Converter Diagnosis

    • Refer to No Torque Converter Clutch Apply
    • Refer to Engine Stall

If no symptoms are found

    • Refer to Fluid Leak Diagnosis
    • Refer to Road Test
    • Refer to Stall Speed Test
    • Refer to Line Pressure Check