Patient came to clinic to evaluate pump malfunction.Walkmed 350vl (b)(4).Pump alarmed at 0300.Patient tried changing battery and called infu system support when pump continued to alarm.He was instructed to clamp pump and come to clinic in am.Port with positive blood return.Pump infused 11 hrs before alarming.When pump checked message displayed er u (system malfunction).New pump was issued to patient and infusion rate adjusted to finish in 46 hrs.