If you have a customer concerned that his/her daytime running lights (DRLs) do not operate, check to see if the brake fluid level warning light is “on.” If it is, the DRLs will not function.

You need to check the brake fluid master cylinder for proper level. If the fluid gets too low, the rubber plunger inside the master cylinder drops down and pushes on the low fluid warning light switch, turning on the dash light. This renders the DRLs inoperative. No repair should be attempted other than bringing the brake fluid to its proper level.

Technical service bulletin courtesy of ALLDATA.

For additional information, visit www.alldata.com.