GOING ABOUT 50 MPH ON INTERSTATE WHEN ENGINE LOST POWER. HAD MULTIPLE WARNING LIGHTS AND MESSAGES, INCLUDING ABS AND SERVICE BRAKES. PULLED OFF ON EXIT RAMP AND STOPPED ON GRASS COMPLETELY OFF TRAVEL LANE. TRIED TO RESTART ENGINE SEVERAL TIMES WITH NO SUCCESS. BEFORE I COULD TAKE OTHER ACTION, I WAS HIT IN THE LEFT REAR BY ANOTHER CAR, WHICH PUSHED MY VEHICLE ABOUT 50 FEET BACK INTO THE TRAVEL LANE. DAMAGE TO REAR QUARTER PANEL, BUMPER, AND TAILGATE. MY VEHICLE HAD TO BE TOWED TO DEALER. DEALER WAS ABLE TO START ON FIRST ATTEMPT. NO PROBLEM FOUND WITH ENGINE. ONLY ABS CODE IN COMPUTER.