Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
1992 GMC Forward Control 6.2 J, AutomaticFACTORY OEM SERVICE PROCEDURE
Engine Controls - Tests W/Codes - Transmission
- Introduction
- Self-Diagnostic System
- Trouble Code Charts
- Component Check Charts
- Code 28, Pressure Switch Manifold Fault
- Code 39, Torque Converter Clutch Stuck "Off"
- Code 53, System Voltage High
- Code 58, Transmission Temp. Sensor CKT (High Temp. Indicated)
- Code 59, Transmission Temp. Sensor CKT (Low Temp. Indicated)
- Code 68, Overdrive Ratio Error
- Code 73, Force Motor Current (Current Error)
- Code 75, System Voltage Low
- Code 81, QDM Fault (Solenoid "B")
- Code 82, QDM Fault (Solenoid "A")
- Code 83, TCC QDM Fault
- Code 85, Undefined Ratio
- Code 86, Shift Solenoid "B" Stuck "On"
- Code 87, Shift Solenoid "B" Stuck "Off"
- Output Speed Sensor Circuit Check (2WD) "C/K/G & P" Series
- Output Speed Sensor Circuit Check (4WD)
- Input Speed Sensor Circuit Check
- Brake Signal Circuit Check
- Torque Converter Clutch (TCC) Circuit Check
- Shift Solenoid "A" Circuit Check
- Shift Solenoid "B" Circuit Check
- Force Motor Circuit Check
Factory Service Tools
Use the Manual With the Right Hardware
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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