you are guessing. there is no need to.Pleasestate country and car, ok 05 Forenza.but what country.?do not confuse Saturn with any Suzuki they are not bothers.not at ALL.what counts is the country and VIN.State side, the car has OBD2 ECU/PCM. and here, we connect ascan tool and see MPH. does yours show good MPH?this is the first test, preventing vast guessing and $$$ wasted and no photos of objects , no guesses.try posting the full symptoms, and let the tech work the issue.1: is Speedo MPH dead, or acting up.?2: is only the odometer dead?and most cars changing out he speedo head, will fail.with out a factory scan tool (id dont care what the saturn did,)on newer cars, you must train the PCM/ BCM to accept a new speedo head. (federal rules....)btw, its all here, read the online FSM ,for how to test and repair the ODOMETER.
http://www.scantool.net/software/alldata-diy-1-month-subscription.htmlon some cars 2004 and newer , use the CAN buss.this is a communications buss all newer cars use, usa.at some point, the ECU tells the BCM the mileage and the BCM send this data to the speedo processor.that is a complex path, and trying to guess, $3000 of electronicsis not a good idea. eg. swapping all 3? 1 by 1?The book shows how to find out , where this path is broken. on old cars, the cable is broken (gears) or head is bad.on new cars, it's vastly more complex, foiling dealer tampers...etc.btw2 there are cheap tools to find these facts.