Notes On Intermittents

If Code P063 is intermittent, ensure vehicle operator is not overrunning set speed by greater than 20 MPH. Trouble code will not set by vacuum leaks or vacuum supply problem. Trouble code can only be set by vehicle exceeding set speed by 20 MPH.

Fig 1: Code P063 Schematic, Vehicle Speed & Set Speed Difference Too High

Courtesy of GENERAL MOTORS CORP.

Fig 2: Code P063 Diagnostic Flow Chart, Vehicle Speed & Set Speed Difference Too High

Courtesy of GENERAL MOTORS CORP.