@Meade you have an OBD-II diagnostics port, which can be scanned with a common code reader. Most auto parts stores have these and let you use them for free. You will always have a secondary o2 code and a data link code, but note all of the codes and I can reference exactly what they are.
4500RPM is the cutoff point that the motor defaults to if you do not have a speed signal, so a broken or disconnected speedo cabe, a slipping dust cap or a failed speed sensor will cause this. There are other faults that will cause an early rev limit, but they are usually down around 3500RPM, such as a bad VVT solenoid or an errant throttle pedal signal. Normal redline and hard cutout for the motor is 6800RPM, just FYI