Hello! Welcome to justanswer!
IT will not alter the odometer and the PCM has to be programmed before you install it. The procedures are pretty basic. See the PDF file below for the instructions on how to change it as well as the location.
CLICK HERE FOR PDF FILE DOWNLOAD
Thank you. The reason I ask is my truck was stolen and it has been now recovered. One of my issues is now the odometer is reading an erroneous mileage (like an extra 50000 miles) impossible , it was gone only 20 days but the crooks screwed up a lot of things. I thought by replacing the ECU I could correct it. In addition, the insurance company is jacking me up over the mileage, by trying to say that the mileage is accurate. Any thoughts on what you would do if faced with a similar problem.
Thank your sir.