GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 1999 🢒 GMC P42 Commercial Chassis 🢒 Engine 🢒 Engine Controls - 6.5L (L57) 🢒 Symptom Diagnosis

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.

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 .

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 Transmission Overheats .
    • Refer to Transmission Overheats at WOT .
    • Refer to High Line Pressure .
    • Refer to Low Line Pressure .
    • Refer to Inadequate Lubrication .
    • Refer to Fluid Leak Diagnosis .
    • Refer to Case Extension Bearing/Seal Failed .
    • Refer to Oil Out the Vent Tube .
    • Refer to Oil Pan Fluid Leak .
    • Refer to Fill Tube Fluid Leak .
    • Refer to Electrical Connector Fluid Leak .
    • Refer to Cooler Connector Fluid Leaks .
    • Refer to Case Extension Fluid Leak .
    • Refer to Manual Shaft Fluid Leak .
    • Refer to Pump Body Seal Fluid Leak .
    • Refer to Vehicle Speed Sensor Fluid Leak .
    • Refer to Output Shaft Seal Fluid Leak .
    • Refer to Line Pressure Plug Fluid Leak .

Noise and Vibration Diagnosis

This category contains the following topics:

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

 

    • Refer to Noise .
    • Refer to Vibration .

Range Performance Diagnosis

This category contains the following topics:

    • Drives in Neutral
    • No Park/Neutral
    • No Reverse
    • Engine stalling
    • No Drive
    • No engine braking
    • No or incorrect gear selection

 

    • Refer to Forward Motion in Neutral .
    • Refer to No Park .
    • Refer to No Reverse .
    • Refer to Engine Stall .
    • Refer to No Torque in Reverse and Third .
    • Refer to Loss of Power .
    • Refer to No Torque in Second Gear .
    • Refer to Loss of Drive .
    • Refer to No Overrun Braking - D1 .
    • Refer to No Engine Braking - D1 .
    • Refer to No Overrun Braking - D2 .
    • Refer to No Engine Braking - D2 .
    • Refer to No Second Gear Engine Braking - D2 .
    • Refer to No Overrun Braking - D3 .
    • Refer to No Engine Braking - D3 .
    • Refer to Engine Starts in Gear .
    • Refer to Shift Lever Indicates Wrong Gear .
    • Refer to No Gear Selection .
    • Refer to Remains in Park .
    • Refer to Difficult to Shift Out of Park .
    • Refer to Does Not Stay in Park .

Shift Quality (Feel) Diagnosis

This category contains the following topics:

    • Erratic shifts
    • Harsh, soft, delayed or slipping shifts
    • Harsh, soft, or delayed engagement

 

    • Refer to Erratic Shift Quality .
    • Refer to Harsh Shifts .
    • Refer to Transmission Slips .
    • Refer to Harsh Shift 3 to 4 .
    • Refer to Harsh Shift 4 to 3 .
    • Refer to Harsh Shift D4 to D3, D2, or D1 .
    • Refer to Soft Shifts .
    • Refer to Delayed Shift 1 to 2 .
    • Refer to Soft Shift 2 to 3 .
    • Refer to Soft Shift D3 to D2 .
    • Refer to Soft Shift 3 to 2 .
    • Refer to No D3 to D2 .
    • Refer to No D2 to D1 .
    • Refer to Harsh Shift D to R .
    • Refer to Soft Shift into R .
    • Refer to Soft Shift R to D .

Shift Pattern

This category contains the following topics:

    • One forward gear missing or slipping
    • One forward gear only
    • Two forward gears only
    • Non-First gear start

 

    • Refer to No First Gear - D1 .
    • Refer to No First Gear - D2 .
    • Refer to No First Gear - D4 .
    • Refer to No Second Gear - D1 .
    • Refer to No Second Gear - D2 .
    • Refer to No Second Gear - D4 .
    • Refer to No Second Gear - D3 .
    • Refer to No Third Gear - D3 .
    • Refer to No Third Gear - D4 .
    • Refer to No Fourth Gear - D4 .
    • Refer to First Gear Only - D4 .
    • Refer to Second Gear Only - D4 .
    • Refer to First and Second Gear Only - D4 .
    • Refer to First and Fourth Gear Only - D4 .
    • Refer to Second and Third Gear Only - D4 .
    • Refer to Third and Fourth Gear Only - D4 .
    • Refer to Second Gear Starts .
    • Refer to Third Gear Starts .
    • Refer to Fourth Gear Starts .

Shift Speed Diagnosis

This category contains the following topic:

Inaccurate or inconsistent shift points

 

Refer to Inaccurate Shift Points .

Torque Converter Diagnosis

This category contains the following topics:

    • Torque Converter Diagnosis
    • TCC does not apply
    • TCC does not release
    • TCC apply/release quality
    • Poor acceleration/No Torque Multiplication
    • Converter Ballooning
    • Engine Stall

 

    • Refer to Torque Converter Diagnosis .
    • Refer to No Torque Converter Clutch Apply .
    • Refer to Torque Converter Clutch Stuck On .
    • Refer to Soft Torque Converter Clutch Apply .
    • Refer to No Torque Multiplication .
    • Refer to Torque Converter Clutch Slipping .
    • Refer to Converter Ballooning .
    • Refer to Engine Stall in Neutral .