I have a 2001 GMC Sierra 1500 pickup with a v-8 engine that the lifters have started making a ticking noise that comes and goes. I have added a product recommended by tech called Lucas Oil treatment. This seemed to help but recently the ticking is louder and I get a "service engine soon" message on my dash that comes and goes.
The service engine soon could be relatd, or could not. A scan of the trouble code should differentiate. As far as the ticking noise, I have seen a couple of these that have had cam and lifter damage. This can be hard to detect, and the heads have to come off to remove the lifter carriers to inspect. If you can determine which cylinder the noise is loudest at, you may be able to isolate it running with the appropriate valve cover removed.