This Preliminary Information communication provides information to the technician about vehicles that have either the truck or the snowplow's headlights are flickering or inoperative. There may be a diagnostic trouble code B2575 and or a B2699 set in the body control module. Technician will need to contact the snowplow manufacturer for additional information on their headlight changeover system. Technician is to refer to the latest version of the General Motors up-fitter integration bulletin 116 for additional information these circuits. Technician can find this information at http://www.gmupfitter.com/, under the "Technical Bulletin" Tab and then "Show all bulletins."