WHILE DRIVING AT 65 MPH VEHICLE WENT ONTO AN EXIT RAMP, SLOWED DOWN TO ABOUT 35 MPH, AND IT TURNED RIGHT. THEN, WENT TO STRAIGHTEN OUT VEHICLE AND STEERING LOCKED UP. RAN VEHICLE OFF THE ROAD INTO EMERGENGY LANE; DID NOT HIT ANYTHING, BUT HURT SHOULDER, POPPED IT, TRYING TO TURN STEERING. COULD NOT GET STEERING UNLOCKED. GMC SENT INVESTIGATOR OUT TO CHECK OUT CAR, AND THEY FIXED EVERYTHING. REPLACED STEERING COLUMN E7680/ PART 267460, COLUMN LOCK/10424050S WHEEL, AND SC4X 267460 (COUNT 2). CLAIM TYPE E OM. REPLACED N4800 533WC0.60, MODULE 1 AT 9381389, SC4X 9381389. CUSTOMER TO SEND INVOICE.*AK