Notes On Intermittents

Code is not set by vacuum leaks or vacuum supply problem. Code can only set when vehicle speed exceeds cruise control set speed by 20 MPH.

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

Courtesy of GENERAL MOTORS CORP.

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

Courtesy of GENERAL MOTORS CORP.