Code 68, Overdrive Ratio Error - 4L80-E Transmission: Notes

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