Hi, first, I replaced the battery. No need to buy the expensive branded battery - in the case of the Hummer H2, just get a standard 12v 12mAh battery and attach the special wiring harness from the old one to it.

I then de-soldered and re-soldered a bad connection on the battery cable.

Then, I took apart the gear shifter and used contact cleaner on all the switches.

Finally, the jeep works!!!

Take care