THE DHC8 CREW SHUT AN ENG DOWN WITH A LOW OIL PRESS WARNING LIGHT. AN EMER WAS DECLARED FOLLOWED BY AN EMER LNDG. THE LIGHT ILLUMINATED BECAUSE A PREVIOUS SENSOR WIRING REPAIR FAILED; SHORTING THE SYSTEM.

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WE WERE IN CRUISE FLT AT FL250 BTWN ZZZ AND ZZZ1. WE HAD REQUESTED A DEV TO THE E TO AVOID A LINE OF TSTMS. WE HAD BEEN CLRED DIRECT WHEN ABLE AND HAD JUST PROCEEDED DIRECT. THE WX RADAR SHOWED ONLY LIGHT PRECIP ALONG OUR RTE WITH OCCASIONAL AREAS OF MODERATE. ALL OF THE AREAS OF SEVERE RETURNS WERE WELL TO OUR W. WE HAD RECEIVED SEVERAL FLASHES OF LIGHTNING AROUND THE AIRPLANE; BUT WE DID NOT BELIEVE THAT WE HAD BEEN STRUCK. WE WERE IN ICING CONDITIONS AND I HAD TURNED THE AUTOPLT OFF TO MAKE SURE WE WERE NOT HAVING ANY ADVERSE SIDE EFFECTS FROM THE ICING CONDITIONS. AFTER A FEW MINS IN CRUISE; THE MASTER WARNING ILLUMINATED AND WE OBSERVED A #2 ENG OIL PRESSURE WARNING LIGHT. I OBSERVED THE OIL PRESSURE WAS NORMAL AND REQUESTED THE FO TO PULL THE EPC FOR THE ENG OIL PRESSURE WARNING LIGHT EMER CHKLIST. HE READ THE CHKLIST VERBATIM AND WE DECIDED THAT THE OIL PRESSURE APPEARED NORMAL. WE WERE UNABLE TO CANCEL THE MASTER WARNING AND THE #2 ENG OIL PRESSURE WARNING CONTINUED FLASHING. AFTER WATCHING THE SITUATION FOR A FEW MINS; WE DECIDED TO SHUT DOWN THE #2 ENG. PRIOR TO SHUTTING THE ENG DOWN; I CALLED OUR FLT ATTENDANT AND HAD HER TAKE HER SEAT AND ADVISED HER THAT WE WOULD BE SHUTTING THE #2 ENG DOWN. I THEN TOLD ZDV THAT WE WOULD BE SHUTTING AN ENG DOWN DUE TO LOW OIL PRESSURE AND WOULD LIKE TO PROCEED TO ZZZ2 AS WE WERE ONLY ABOUT 15 NM NE OF THE FIELD. ATC CLRED US TO 10000 FT AND I INITIATED A DSCNT. AS WE WERE DSNDING; I CALLED FOR THE ENG/FIRE/FAIL SHUTDOWN CHKLIST AS CALLED FOR BY THE ENG OIL PRESSURE WARNING LIGHT CHKLIST. I INSTRUCTED THE FO TO JUST READ THE CHKLIST SINCE THERE WAS NO REAL REASON TO PERFORM IT FROM MEMORY. WE COMPLETED THE CHKLIST TO THE 1 ENG INOP EMER CHKLIST. I THEN HAD THE FO BRIEF THE FLT ATTENDANT. WE INSTRUCTED HER THAT THERE WOULD BE NO NEED TO BRACE OR EVAC AND THAT WE WOULD BE STOPPING ON THE RWY. WE REQUESTED CFR IN ZZZ1 AS A PRECAUTION. NEXT; WE CALLED COMMERCIAL RADIO AND ATTEMPTED TO CONTACT DISPATCH. THE FO HAD NEVER CALLED COMMERCIAL RADIO BEFORE; SO I HELPED HIM WITH THE CONTACT PROC. WE WERE INITIALLY TOLD TO STAND BY. WE THEN INSTRUCTED THEM THAT WE HAD AN EMER AND RECEIVED SVC. WE INFORMED DISPATCH THAT WE WOULD BE PROCEEDING TO ZZZ2 AND WOULD NEED LNDG DISTANCE NUMBERS. THE ANTISKID HAD BEEN MEL'ED IN ZZZ. AFTER WAITING FOR ABOUT 10 MINS; WE FIGURED THE NUMBERS FOR OURSELVES AND DETERMINED THAT WE COULD LAND ON EITHER RWY AT ZZZ2 AND INFORMED DISPATCH THAT WE HAD THE NUMBERS AND WOULD TALK TO THEM ON THE GND. COMMERCIAL RADIO WAS HARD TO READ AT 10000 FT NEAR ZZZ2. THERE WERE TSTMS IN THE AREA AND AS SUCH HAD BEEN REQUESTING HDGS FROM CTR THAT KEPT US OUT OF THE TSTMS AND IN THE VICINITY OF ZZZ2. THE FO OBTAINED THE WX FOR ZZZ2 AND WE DECIDED ON RWY 30 SINCE IT HAD AN ILS AND THE WINDS WERE 050 AT 5 DEGS. WE CIRCLED OVER THE ARPT WHILE RUNNING THE 1 ENG IN RANGE CHKLIST TO THE 1 ENG LNDG CHKLIST. I THEN JOINED A DOWNWIND FOR RWY 30 AND I HAD THE FO REVIEW THE 1 ENG LNDG CHKLIST. I THEN TURNED ABOUT A 15 NM FINAL AND SET MYSELF UP FOR A 30 DEG INTERCEPT FOR THE ILS. I TURNED THE AUTOPLT OFF AND ENTERED APCH MODE FOR THE ILS. WE JOINED THE LOC AND RAN THE 1 ENG LNDG CHKLIST. WE THEN LANDED IN ZZZ2 WITHOUT FURTHER INCIDENT AND STOPPED ON THE RWY SHORT OF RWY 5/23. THEN WE RAN THE NORMAL SHUTDOWN CHKLIST AND HAD THE PAX REMAIN SEATED. WE DECIDED THAT SINCE IT WAS RAINING AND THERE WAS NO TRANSPORTATION FOR THEM THAT WE WOULD LEAVE THE DOOR CLOSED AND WAIT FOR THEM TO GET A RIDE. WE CALLED ATC AND DISPATCH TO LET THEM KNOW WE WERE ON THE GND SAFELY. WHEN WE ARRIVED THE NEXT MORNING MAINT INFORMED US THAT THEY HAD DISCOVERED THE SOURCE OF THE PROB. AT SOME POINT IN THE PLANE'S LIFE; THE WIRES LEADING TO THE OIL PRESSURE SENSOR HAD WORN OFF AND HAD BEEN REPAIRED BY USING THE AVIATION EQUIVALENT OF ELECTRICAL TAPE TO RE-INSULATE THE WIRES. THE WIRES WERE THEN TAPED TOGETHER. OVER TIME; THE TAPE WORE OUT AND WITH THE WIRES NEXT TO EACH OTHER; THEY EVENTUALLY SHORTED OUT CAUSING OUR CAUTION LIGHT TO ILLUMINATE.