My 2012 grand Cherokee 5.7 liter will not start & etc light comes on..solution ??

SOURCE: 1995 jeep grand cherokee power loss

could be engine mounts have to replace mine engine almost jumps outta the compartment

SOURCE: 2000 jeep grand cherokee 4.0 liter engine timing belt replacement

If you have the same pulley arrangement that most 4.0 engines have that pulley is an idler not a tensioner. Your power steering pump has a pivot bolt, and a slide under the pump. You adjust belt tension using the pump.

SOURCE: 2003 Jeep Grand Cherokee check engine light stays

go to autozone they will check codes for free

SOURCE: all warning lights on dash come on and all electrics stop working

The common problem with the dashes on the Jeep is contacts. Remove the cluster and try cleaning the electrical contacts with a Q-tip and alcohol replace cluster and try again.

SOURCE: 2005 jeep grand cherokee 3.7 liter p0303 code

Most likely ,even though you have a 303 code, that
it wasn't that cylinders coil that failed

Need to put the old coil back & walk new one to different
cylinder or use a professional scan tool in Mode $06 ,to see
the misfire counts on all cyl's

Unrelated,I would loose the front O2 sensors after 7 years
& 100,000 miles

Never need to do plugs to diagnose problems
Only do plugs every 3 years a preventative maintenance