GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2009 🢒 Sierra Denali 🢒 Transmission 🢒 Automatic Transmission - 6L50/6L80/6L90 🢒 Symptoms - Automatic Transmission

Important: Use the symptom tables only if the following conditions are met:

   • Refer to Diagnostic Starting Point - Vehicle.
   • There are no DTCs set.
   • The control modules can communicate via the serial data link.
   • Review the system operation in order to familiarize yourself with the system functions. Refer to Transmission General Description and Transmission Component and System Description.

Visual/Physical Inspection

Inspect the easily accessible or visible system components for obvious damage or conditions which could cause the symptom.

Intermittent

Faulty electrical connections or wiring may be the cause of intermittent conditions. Refer to Testing for Intermittent Conditions and Poor Connections.

Symptom List

Refer to a symptom diagnostic procedure from the following list in order to diagnose the symptom:

    • Fluid Diagnosis
       -  Transmission Fluid Check
       -  Fluid Pressure High or Low
       -  Automatic Transmission Fluid Leaks
       -  Fluid Leak Diagnosis
    • Noise and Vibration Diagnosis
       -  Whine/Growl Noise That Changes with Vehicle Speed
       -  Noise in First or Reverse Gear
       -  Noise in First, Second, Third, Fourth, Fifth, or Reverse Gear
       -  Noise in First, Second, Sixth, or Reverse Gear
       -  Noise in Second or Sixth Gear
       -  Noise During 3-4 or 4-3 Shifts
       -  Noise in Fourth, Fifth, or Sixth Gear
       -  Vibration
       -  Vibration in Second, Third, Fourth, Fifth, or Sixth Gear
       -  Flex Plate/Torque Converter Vibration Test
       -  Noise and Vibration Analysis
    • Range Performance Diagnosis
       -  No Park or Drive
       -  No Drive in All Ranges
       -  No Reverse Gear
       -  No Drive or Reverse Gear
    • Shift Quality Feel Diagnosis
       -  Harsh Garage Shift
       -  Harsh, Soft, Delayed or Slipping First or Reverse Gear
       -  Harsh, Soft, Delayed or Slipping 1-2-3-4 Shift
       -  Harsh, Soft, Delayed or Slipping 4-5-6 Shift
       -  Harsh, Soft, Delayed or Slipping Third, Fifth, or Reverse Gear
       -  Harsh, Soft, Delayed or Slipping Second or Sixth Gear
    • Shift Pattern
       -  No First Gear
       -  No First and Reverse Gears
       -  No First, Second, Third, and Fourth Gear
       -  No First, Second, Third, Fourth, Fifth, or Reverse Gear
       -  No Second and Sixth Gear
       -  No First, Second, Sixth, or Reverse Gear
       -  No Fourth, Fifth, and Sixth Gear
       -  No Third, Fifth, and Reverse Gear
       -  Stuck in Second or Sixth Gear
       -  Stuck in First or Reverse Gear
    • Torque Converter Diagnosis
       -  Torque Converter Diagnosis
       -  No Torque Converter Clutch Apply
       -  No Torque Converter Clutch Release
    • Symptom Not Found or No Symptom Detected
       -  Transmission Fluid Check
       -  Road Test
       -  Line Pressure Check