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.
DTC 68, Transmission Component Slipping (4L80-E): Notes
1995 GMC Suburban K2500, 7.4 NSECTION Notes
PCM monitors difference in engine speed and input speed. With transmission in Drive and TCC locked, scan tester should display engine speed closely matching input speed. DTC 68 will set when:
- DTCs 28, 71 or 74 are not set.
- TCC slip speed greater than 200 RPM.
- 4th gear is indicated.
- TCC is locked.
- Not in Park/Neutral.
- All conditions are met for 2 seconds.
PCM will default to inhibit TCC operation.
NOTE:
Test numbers refer to numbers on diagnostic chart.
- This test checks the indicated range signal to actual selected range. A faulty switch could set DTC 68.
- This test checks torque converter for slippage while in commanded lock-up state.
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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.