2002 BMW 325

Engine Cooling problem
2002 BMW 325 6 cyl Automatic 67000 miles

HI, I BOUGHT THIS CAR 1 YR AGO IS A 2002 BMW 325i, WHEN I BOUGHT IT ON THE DEALER SHIP THEY DID NOT SHOWED ME, THE PREVIOUS RECORD OF THE CAR, LATER I FOUND OUT THAT HAD ALREADY BEEN CRASHED, THE CAR STARTED TO HAVE A BAD PERFORMANCE, ENGINE SERVICE LIGHT TURNED ON, I HAD TO CHANGED THE GAS FILTER AND I ALSO HAVE CHANGED THE WATER TEMPERATURE SENSOR THAT IS LOCATED NEXT TO OIL FILTER AND THE LIGHT WILL CONTINUE TO TURN ON AGAIN, SO I WENT TO AUTO ZONE FORM THEM TO CHECK THE LIGHT AND THEY GIVE ME A REPORT WITH A CODE (P0128), SO I STARTED TO SEARCH ON WEB TO SEE WHAT DID I HAD TO REALLY CHANGED BUT NOW I AM CONFUSED BECAUSE I HAVE SEEN THAT THEY MAY BE 2 DIFFERENT TYPES OF SENSORS THAT MAY CAUSE THE LIGHT TO KEEP ON TURNING ON, BUT I AM NOT REALLY SURE IF THIS TYPE OF CAR HAS 2 SENSORS, THE REASON I NEED TO FIX THIS PROBLEM IS BECAUSE I HAVE TO GET NEW LICENSE PLATES AND I WILL NEED TO GO FOR A EMISSION TEST AND I AM AFRAID THAT THE CAR WOUN'T PASS IT BECAUSE THE ENGINE LIGHT IS ON, CAN YOU PLEASE HELP ME OUT TELLING ME IF YOU KNOW WHAT TYPE OF SENSOR OR PART WILL I NEED TO CHANGE AND WHERE DOES EXACTLY IS LOCATED OR IF NEED REMPLACE THE THERMOSTAT AND CHANGE THE ANTIFREEZE THANKS FOR YOU HELP