you can check them with a test light and a jumper wire,there is a black plug under the hood on the pass. side by the fire wall and a single wire plug. hold that plug in your hand with the 4 wires on the bottom, 2 on top. connect the single wire plug to the top right wire with a jumper wire.connect the test light wire to the pos. side of the battery,then push the metal part of the test light into the 2nd hole from the left on the bottom 4 wires.turn your key on and watch the test light or check engine light for the codes.
check out the 35ththuderbirdregistry.org site for more detailed instructions.you can do either key on egine off or key on engine runnig tests.
good luck.
joe