Code 68, Cruise System Problem: Notes

Fig 1: Code 68 - Schematic

Courtesy of GENERAL MOTORS CORP.

PCM-controlled cruise control system monitors itself to ensure desired and actual cruise control servo positions are equal. Code 68 sets if actual servo position sensor signal is 15 percent greater than desired signal for .6 second. Code 68 does not turn on SERVICE ENGINE SOON light. If Code 68 is current, vehicle will operate in power management mode. During this mode, PCM will shut off fuel to 3 cylinders to prevent excessive engine RPM if throttle is held open by cruise system malfunction. Power management mode may be perceived as a severe engine miss or lack of power.

1. Most servo vacuum solenoids leak a small amount of vacuum when closed, however, they should not leak enough to allow WOT in 15 seconds with vent closed.
2. When vacuum solenoid is forced on, vacuum will be vented to atmosphere unless vent valve is stuck closed.