Code 12 Won't start

I have a 1995 Cherokee that won't start unless I jump start it. When I turn the key to on it seems like the voltage pulses, you can see the lights dim and the radio goes on and off. When running the voltage is 14 volts and battery alone not running is 13 volts. I hear a high pitch sound near the front passanger side when the key is on. Sounds like it may be comming from a module on the fender wall. When I check the code I get 12. Any thoughts would be appreciated.

Thanks
Mike

Not sure, but it sounds like the voltage isn't making it from the battery to the starter. Since the extra voltage seems to push through, I'd check the positive battery cable. If it's corroded (on the inside of the insulation) it would reduce the amount of juice available. I had one vehicle that died because of that problem, replaced the cable and it was good to go.

It ended up being a bad battery. It had the voltage but not the amps when tested. Thanks for the help.

Don't you love it when it's a simple problem!!

CODE 12 is battery disconnected within last 50 cycles.