One problem related to transmission failure has been reported for the 2003 Mazda Protege. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2003 Mazda Protege based on all problems reported for the 2003 Protege.
My transmission completely failed at 18,000 miles and one month shy of being a year old. A new transmission was installed. I had my car back for one week and the new transmission would down shift for no reason as I was doing 70 mph down the interstate. After replacing the computer, throttle position sensor, throttle range sensor, and the engine wiring harness, Mazda has now decided to replace the new transmission. This will be the third transmission in a year old car.