This will likely prevent the cruise control from functioning correctly, as the system is confused by the constant signal. It might also cause other issues depending on how the faulty signal interacts with other systems.
You'll need to have the speed control switch replaced to resolve this issue. It's a relatively straightforward repair, but it's recommended you have a qualified mechanic do it, or at least consult a repair manual specific to your year and model PT Cruiser. Attempting to fix this yourself might involve disassembling parts of the steering column.
