My 07 runs and drives like a dream, except when for no reason while driving at any speed, all the dashboard lights go on, beeping and guages JUMP to 70mph, Tach goes to 6,000 rpm and Temp jumps from normal to hot, and the radiator fan goes to "supersonic". I've replaced the RCM with a rebuilt "upgraded" one. I've installed a 4 guage ground cable from the - battery terminal to the Bell Housing on the Transmission. And years ago completely disconnected the alarm system/siren. DOES ANYONE KNOW HOW TO FIX THIS??? Please help!

Parked with key out of the ignition. What could the problem be?