GM Service Manual Online
For 1990-2009 cars only

Diagnostic Category

Diagnostic Information

DEFINITION: The following table consists of eight diagnostic categories that are located in the left 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 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 Fluid Foaming .
    • Refer to High or Low Line Pressure .
    • Refer to Fluid Leak Diagnosis .
    • Refer to Automatic Transmission Fluid Leaks .

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 Ratcheting Noise .
    • Refer to Noise .
    • Refer to Vibration .

Transmission Will Not Upshift or Downshift

This category contains the following topic:

Using TAP Shift

Refer to TAP Shift Circuit Performance .

Range Performance Diagnosis

This category contains the following topics:

    • Drives in Neutral
    • No Park
    • No Reverse
    • No Drive
    • Loss of power
    • No engine braking
    • Shift indicator indicating wrong gear
    • No gear selection
    • Refer to Drives in Neutral .
    • Refer to No Park .
    • Refer to No Reverse or Slips in Reverse .
    • Refer to Loss of Drive .
    • Refer to Loss of Power .
    • Refer to Engine Stall .
    • Refer to No Engine Braking; All Manual Ranges .
    • Refer to No Gear Selection .

Shift Quality, Feel, Diagnosis

This category contains the following topic:

Harsh shifts

Refer to Harsh Shifts .

Shift Pattern

This category contains the following topics:

    • One forward gear only
    • Specific forward gears only
    • Slipping
    • Refer to Second Gear Only .
    • Refer to First and Second Gears Only .
    • Refer to First and Fourth Gears Only .
    • Refer to Second and Third Gears Only .
    • Refer to Third and Fourth Gears Only .
    • Refer to No First Gear, Slips in First Gear .
    • Refer to No Second Gear, Slips in Second Gear .
    • Refer to No Third Gear, Slips in Third Gear .

Shift Speed Diagnosis

This category contains the following topic:

Inaccurate or inconsistent shift points

Refer to Inaccurate/Inconsistent Shift Points .

Torque Converter Diagnosis

This category contains the following topics:

    • Torque Converter Diagnosis
    • TCC remains engaged
    • TCC application while engine is cold
    • TCC shudder
    • Engine stalling
    • Refer to Torque Converter Diagnosis .
    • Refer to No Torque Converter Clutch Release .
    • Refer to Torque Converter Clutch Shudder .
    • Refer to Engine Stall .

If no symptoms are found

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