Does the dx have passenger door solenoid? i.e the passenger door unlocks from the drivers door lock?
I fitted a keyless set up to my 03 ST ute which involved fitting genuine door latch/solenoid assy to drivers door from a wagon, running two wires for the lock/ unlock solenoid to under the centre of the dash (just behind the lighter socket is the control module for the passenger door on the ST) and activating it by an alarm kit through the lock and unlock negative trigger feeds that come from the drivers door window control panel and go to the module. Most off the shelf alarm kits have the functions to operate central locking. They just need to be wired to suit which is in the diagrams supplied.
I fitted a keyless set up to my 03 ST ute which involved fitting genuine door latch/solenoid assy to drivers door from a wagon, running two wires for the lock/ unlock solenoid to under the centre of the dash (just behind the lighter socket is the control module for the passenger door on the ST) and activating it by an alarm kit through the lock and unlock negative trigger feeds that come from the drivers door window control panel and go to the module. Most off the shelf alarm kits have the functions to operate central locking. They just need to be wired to suit which is in the diagrams supplied.