05 JEEP TECH QUESTION

No inertia switch in 05 Grand Cherokee, anti theft would prevent cranking. Could be lots of different things, that require various ways of testing and some electrical smarts. Examples - crank position sensor, cam sensor, either can fail without setting a fault code. Wiring - corrosion almost anywhere in the harness. Also, depending on where the OP got his parts - they could be inferior / failing right out of the box. Look up how to bypass a relay, and try that, make sure the terminals that the relay plugs into are tight fitting. I wouldn't recommend throwing any more parts at it without an accurate diagnosis. Sometimes we can help, other times, you just need to bite the bullet and take it in.