I purchased an '08 Chevrolet Suburban LTZ from a dealer in February of 2015. Within 2 days a warning came on that said 'Service Suspension' or something to that affect. I took it back to the dealer where I purchased it, they claimed to order a part and repair it. NOW, we are having issues with the air ride system and upon further inspection we discovered that rear air shock (that they claimed to fix) is split. It appears to have been that way for a lengthy amount of time. The true question of this thread, when checking the fuses, the 40amp fuse (54) that I was told to check has a white 'X' drawn on it. Has anyone ever had a fuse with an 'X' drawn or have you drawn an 'X' on a fuse? Why? Is there a module that can be purchased by a dealer to override the air ride suspension system to prevent the display of an error code on the instrument panel?

 

My 2¢ is the X is likely from the factory / assembly plant. When that option was installed the line worker doing the inspection probably made the mark as part of a quality check verifying that the part was there.
The color of the mark could be an indicator of the shift or inspector it was done by... As long as the fuse is good the X is likely irrelevant..