I ran into this problem about 2 months ago when I installed a dual battery kit in my 08 Rubi Unlimited. It turned out to be something simple. I discovered that a fairly major connector had come loose. It ran along side the battery towards the TPIM and was located between the battery-TPIM and the engine. Once I plugged the connectors back together everything worked great.
2008 Rubi Unltd • RR Roll Cage - Limb Risers - Evap Skid - Diff Covers • PolyPerf HD Ball Joints • Reid Hi Steer Knuckles • RK 3.5" Triple Threat PRO Longarm • Rebel F & R Coil Overs • sPod Mini • Shrockworks Rock Sliders - Rear Bumper w/ Tire Swing • Xenon Flat Flares • ORO Onboard Air • BD Dual Battery • 5.13 Gears • 35" BFG KM2s • Warn VR12000 Winch • Safari Straps Everything • Tuffy Security Drawer •