problems remote starting when hot outside

Yup that grinding sound is the starter engaging again even though the engine is running, which says that the tach is faulty, either it needs to be re-learnt or the wire needs replacing, try the relearn firstly it's the easier thing to start with.

Also i'm not sure but doesn't that bypass connect to the keysense wire which would cause the bypass to drop out when you insert the key you use to start the vehicle, i'm almost certain it does, if this is the case then the bypass was ruled out a long time ago.

if its a 556uw bypass with the keybox the harness only has power, ground and the blue/white, i think

I said i was almost certain, i didn't say i was sure that it had the keysense.

i know thats why i said i think those are the only colors....its been a while since i used a 556uw