1999 Jeep Cherokee Air bag light on/no horn

Several months back, we had some work done (at the dealership) on the wiring harness because the air bag light would occasionally come on and all the gauges would go dead. Everything worked fine for a couple of months, but now the airbag light is on constantly, the horn won't honk, and only the front speakers work. Dealership says there is no connection to the work they did...
Any thoughts