You could try the key dance method to see if it blinks out any codes, but that probably wont help fixing the port connection problem. Sounds like a wiring or ECM problem. Repair any obvious damaged wires, otherwise check and clean the ECM connectors under the hood.
If you bought the ZJ from a reputable dealer, take it back and complain. If you bought it "as is" on CL, good luck.
06 Laredo - 4x4 V6 - Stone White - Custom LED Cargo Area Lights, Lighted Visors Added - now at 49k miles
97 Laredo - 4.0 4x4 Daily driver for 8 years then relocated to Arizona for 6 more years with the relatives