Ahh.... Google! Heated seat wiring seems not impossible. Seems there's a relay needed, and a new spot on the fuse block. Also have to figure out which wires do what on the big 7(?)-pin connector.
http://www.allpar.com/forums/topic/142419-heated-seats-in-a-non-heated-seat-car/
"PT CRUISER HEATED SEAT SYSTEM - DESCRIPTION
Individually controlled, electrically heated front seats are available factory-installed optional equipment on this model. Vehicles with this option can be visually identified by the two separate heated seat switches mounted on each of the seat cushion side shields. The heated seat system allows the front seat driver and passenger to select from two different levels of supplemental electrical seat heating, or no seat heating to suit their individual comfort requirements. The heated seat system for this vehicle includes the following major components, which are described in further detail later in this section:
Heated Seat Elements - Two heated seat elements are used per vehicle, one for each front seat. The heated seat elements are integral to the front seat and seat back cushions. Refer to the description of the heated seat elements later in this section for additional information.
Heated Seat Modules - Two heated seat modules are used per vehicle. One module is mounted to each of the power seat cushion pans, under the forward edge of each front seat. Refer to the description of the heated seat module in the electronic control modules section of the service manual for additional information.
Heated Seat Relay - One heated seat relay is used per vehicle. The relay is located in the instrument panel fuse block, on the left lower side of the instrument panel.
Heated Seat Sensors - Two heated seat sensors are used per vehicle, one for each front seat. The heated seat sensors are integral to each of the heated seat cushions.
Heated Seat Switch - Two heated seat switches are used per vehicle, one for the driver and one for the passenger side front seats. The switches are mounted to each of the front seat cushion side shields. Refer to the description of the heated seat switch later in this section for additional information.
Hard wired circuitry connects the heated seat system components to each other through the electrical system of the vehicle. These hard wired circuits are integral to several wire harnesses, which are routed throughout the vehicle and retained by many different methods. These circuits may be connected to each other, to the vehicle electrical system and to the heated seat system components through the use of a combination of soldered splices, splice block connectors and many different types of wire harness terminal connectors and insulators. Refer to the appropriate wiring information. The wiring information includes wiring diagrams, proper wire and connector repair procedures, further details on wire harness routing and retention, as well as pin-out and location views for the various wire harness connectors, splices and grounds.
HEATED SEAT MODULE - DESCRIPTION
Two heated seat modules are used on each vehicle equipped with the heated seat option. One heated seat module is located on each power seat track, where they are secured with two push-in type plastic fasteners. The modules are contained within a small, rectangular, molded plastic housing with a single connector receptacle that allows them to be connected to all of the required inputs and outputs through the power seat wire harness. The heated seat modules are electronic microprocessor controlled devices that are designed to monitor the inputs and control the outputs of the heated seat system. The heated seat modules are programmed to provide two levels of heating for each front seat: a Lo temperature set point of about 36° C (97° F), or a Hi temperature set point of about 41° C (105° F) The heated seat modules are also programmed to perform self-diagnosis of certain heated seat system functions. Refer to heated seat module diagnosis and testing for additional information. The heated seat modules cannot be adjusted or repaired. If a module is damaged or faulty, the entire module must be replaced."
Also,
Re: Need help installing heated seats please!
I wanted to do exactly the same thing to my wife's '01. In the first place the local Chrysler dealer service manager told me that it could not be done since the ecm(?) would not have the proper circuitry(or something) and it was a high risk to add something that it wasn't designed for. But since I already had purchased the heated seats I decided to do it anyway...what they were telling me did not make good common sense since 12v can't pull more than what you fuse it with. I just went from the fused side of the main panel to a seperate little auxiliary panel I bought and mounted it beneath the steering column under that little plastic panel. I fused each circuit going out to the seats seperately and have had no trouble whatsoever. I think there is also a lumbar thing there too as well as the air bags (be careful messing with those). It's been so long since I did it I can't remember the specifics, but I just tried to use lower value fuses as I went out from the main oem panel. The dealer didn't have much to say when I took it back to them and proved them wrong. Makes me wonder if there are any old-school mechanics left out there that can actually figure something out without plugging in a scanner.