No, nothing whatsoever.
The 2003 GMC Envoy inline 6 engine does not have a timing belt but a timing chain. No need to replace anything unless the chain breaks.
There are several. Anything newer than 2007 will typically employ a timing chain instead.
timing chain timing chain
Timing Chain
The 4 cylinder has a timing chain but the V6 has a timing belt. The belt on the V6 must be replaced at 110,000 miles or 10 years whichever comes first. No maintenance is required on the 4 cylinder chain.
timing chain timing chain
timing chain timing chain
You do not have to do anything. It is recommended on some vehicles, but not many. Timing chains usually last the life of the engine with no maintenance.
No Belt=It has a Timing Chain.=
It has a timing chain
Timing chain
It has a timing chain.