Code 68, Overdrive Ratio Error: Notes

WARNING: This page does not describe the selected car, but rather 10 other vehicles, including the 1994 GMC Yukon, 1994 GMC Suburban, 1994 GMC Pickup, 1994 GMC Cab & Chassis, and 1994 GMC C3500 HD. However, it is still accessible from the selected car via links, so may be relevant.

The PCM/TCM monitors the difference in engine RPM and input shaft RPM. With transmission in Drive, scan tester reading should show engine speed closely matching input speed.

NOTE: Test numbers refer to numbers on diagnostic chart.

Checks the indicated range signal to the selected range. A faulty switch could set this code.
Checks TCC for slippage while in a commanded lock-up state.