Any idea why the keyelss entry system would quit "chirping" the horn and re-locking the vehicle when the lock button on the fob is pressed a second time? I'm guessing that the module may be suspect.
May be try recoding the FOBS to the Van. Turn the key eight times on and off with out starting the vehicle. When the power door locks cycle up and down press the lock button on one FOB then the unlock button on the other FOB. This will recode them. The key needs to be in the run position to this.