1996 Dodge Dodge Truck

EVERY WEEK THIS PAST MONTH I HAVE BEEN TAKING MY CAR INTO THE NELSON DODGE DEALERSHIP IN EL MONTE, CALIFORNIA IN REGARDS TO THE SERVICE ENGINE LIGHT KEEPS COMING ON. THE DEALERSHIP CANNOT FIND OUT WHAT IS WRONG WITH THE CAR. THEY "THINK" IT MAY NEED POWERSTRAIN CONTROL MODULE AND MAP SENSOR. THE DEALERSHIP IS NOT SURE. I TOOK THE VAN IN ON 10/15/01 DUE TO THE CHECK ENGINE LIGHT AND I WAS CHARGE FOR REPLACING THE THERMOSTAT AND GASKET. ON 10/23/01, MY VAN STALL WHILE DRIVING AND I TOOK IT IN AND WAS CHARGE FOR THE THROTTLE BODY SERVICE. ON 10/29/01 I NOTICE A GREEN LIQUID THAT WAS DRIPPING AND THE DEALERSHIP SAID IT WAS THE COOLING SYSTEM, THEY CHECK IT AND FOUND NOTHING WRONG, I WAS NOT CHARGED. ON 11/05/01, I TOOK IT IN AGAIN FOR THE SERVICE ENGINE SOON LIGHT WAS COMMING ON AGAIN, THEY CHECK THE VAN AND WERE NOT ABLE TO DETECT A PROBLEM, THEY "THINK" IT MIGHT NEED POWERSTRAIN CONTROL MODULE AND MAP SENSOR. ON 11/06/01, THE SERVICE ENGINE SOON LIGHT HAS BEEN GOING ON THEN IT TURNS OFF, I HAVE IT IN THE DEALERSHIP AGAIN, WAITING TO RECEIVE A CALL FROM THE DEALERSHIP AS TO WHAT THEY "THINK" MIGHT BE THE PROBLEM, THAT'S IF THEY DETECT A PROBLEM.