I have a 99 F-150.I started my truck and it blew a spark plug which caused the service engine soon light to come on.I had it taken to a auto machine shop to get fixed.mechanic called and said fixed spark plug problem but service engine light wont reset, his computer wasnt picking up any codes.Im going to disconnect the battery if he didnt already.Any other suggestions? Thanks

 

Just to touch all the bases, once the lite comes on and the problem is corrected , you need a scan tool to turn off the light , or like several trips where the problem no longer exists, or just maybe there is a new problem the computer is picking up. The previous post said it well, you need a scan tool! Autozone will provide that service free of charge.
Once you get the codes , then you can move on to removing the cause.

 

When all else fails, you just cover it up with a piece of black electric tape...