Need Help, My steering sensor, airbag sensor went out, key fob quit same event

Hello,

I own a 2009 Tacoma Toyota, four wheel drive, four door 83000 miles. I have had it for a little over a year, runs great, does well. All of the sudden one day, the little yellow car with squiggle lines comes on as well as the generic air bag light, and the passengar air bag light on the dash goes to off. The only the thing I have ever had done to this is add an amp about a year prior to this event. So, my airbags don't work and my key fob doesn't work, it is all tied to the ECU? computer, so says the dealer, but they have no clue as to the issue. They replaced the steering angle sensor and the error code went away, but the light stayed on the dash display, along with the generic airbag light and the key fob failure, they could not get it to program. The mechanic said the computer was not receiving any information, but seemed to be working fine. He wanted to put a completely new harness in the thing....please, help.