2004.5 sportsman 500 help!

Got a new battery that had the poles reversed and hooked it up backwards. Got a puff of smoke from under the front, also a sizzle noise. Put in correct battery and had no power to switch. put a volt meter between battery and neg. cable and was reading 12.84 volts, same as battery. does this mean I have a dead short? When i disconnected the ecm it dropped to 12.06 volts, when I unplugged the speedo it stayed at 12.84 until i unplugged the ecm also then it dropped to zero. does this mean the ecm is bad or both ecm amd speedo? I can not find any burnt wiring or sign of damage anywhere, although ecm smells burnt. How can I tell what is really bad without just buying parts? By the way the 04 1/2 had the first ecm that had the circuit breakers built in with the regulator and temp control box that is called the SSCB on the wiring diagram or ecm or logic box in the manual. Thanks for any help anyone can give me. JT