Note On INTERMITTENTS

If an intermittent Code B121 is being set, manipulate related wiring. When BCM BI82 displays change-of-state, an "X" will be indicated. Check circuit for an intermittent open or short.

Fig 1: Code B121, Schematic, Twilight Enable Switch Ckt

Courtesy of GENERAL MOTORS CORP.

Fig 2: Code B121, Flow Chart, Twilight Enable Switch Ckt

Courtesy of GENERAL MOTORS CORP.