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I bought my car 1 year ago and having the DTC 5503 recovery time during filling of central reservoir takes to long.
to start troubleshoot and look for leaks at struts, reservoir in back, valve pack, I checked my pump first. Something is not right , instead of an airfilter I have the Tube connected to a sensor, seems like a pressure sensor. ( when I unscrewed the clamp the sensor has a pointy end).
also the car makes loud hising/ pressure releif sounds, noticable when coming to traffic light stops etc.
I'm willing to bet that pointy ended sensor that someone has jammed in there is your outside temperature sensor. Should go on the front bumper. Just judging by what it sounds like from your description.