We had exactly the same problem on our 01 Elantra. Took it to the dealer
and they repaired it with no problems. This is what they wrote on the
invoice, if it helps :
62456 warr hooked up scan pro and found PO507 idle expected to HI. found
hole in pvc hose. replaced hose and cleared codes. roadtested and verified
repair. the hose wasn't covered on the warranty though, cuz it's a hose!