GM Service Manual Online
For 1990-2009 cars only

Diagnostic Category

Diagnostic Information

Important: The Functional Test Procedure should be performed before beginning any diagnosis. If this procedure has not already been performed, refer to Functional Test .

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 High or Low Oil Pressure .
    • Refer to Fluid Leak Diagnosis (procedure).
    • Refer to Transmission Component Fluid Leaks .
    • Refer to Oil Out the Vent or Foaming .

Noise and Vibration Diagnosis

This category contains the following topics:

Torque Converter Diagnosis (procedure)

Refer to Torque Converter Diagnosis .

Range Performance Diagnosis

This category contains the following topics:

    • No Park
    • No Reverse
    • No Drive
    • No engine braking
    • Refer to Vacuum Modulator Diagnosis (procedure).
    • Refer to No Park Range .
    • Refer to No Reverse .
    • Refer to Slips in Reverse .
    • Refer to No Drive in Drive Range .
    • Refer to Slips in Drive .
    • Refer to Locked Up in Drive/Reverse .

Shift Quality (Feel) Diagnosis

This category contains the following topics:

    • Harsh shifts
    • Soft Shifts
    • Harsh engagement (garage shifts)
    • Delayed engagement (garage shifts)
    • Shift shudder
    • Refer to Vacuum Modulator Diagnosis (procedure).
    • Refer to Harsh or Soft 1-2 Shift Feel .
    • Refer to Harsh or Soft 2-1 Shift Feel .
    • Refer to Harsh or Soft 2-3/3-2 Shift Feel .
    • Refer to Harsh or Soft 3-4/4-3 Shift Feel .
    • Refer to Delayed Engagement .
    • Refer to Shudder 1-2 Shift .

Shift Pattern

This category contains the following topics:

    • No upshift
    • One forward gear only
    • Two forward gears only
    • Non-first gear start
    • Refer to No 2-3 Shift .
    • Refer to No 3-4 Shift .
    • Refer to First Gear Only .
    • Refer to Third Gear Only .
    • Refer to Third and Fourth Gear Operation .
    • Refer to Second Gear Starts .
    • Refer to Third and Fourth Gear Operation .
    • Refer to Fourth Gear Starts .

Shift Speed Diagnosis

This category contains the following topic:

Incorrect shift points

Refer to High or Low Upshift or Downshift Speed .

Torque Converter Diagnosis

This category contains the following topics:

    • Torque Converter Diagnosis
    • TCC does not apply
    • TCC does not release
    • TCC shudder
    • Refer to Torque Converter Diagnosis .
    • Refer to No Torque Converter Clutch Apply .
    • Refer to Converter Clutch Does Not Release .
    • Refer to Harsh Torque Converter Clutch Apply .