Why do I not have any acceleration

I have a 2005 Nissan Murano se I've replaced the alternator, the accelerator pedal sensor, the throttle control body, and the thermostat as the codes was throwing up on the obdm. I have tried clearing it out and the codes go away for a minute but come right back. I also did the relearn on it. Help me please...codes are 1122...etc actuator malfunction.....1126 thermostat stuck open...but I replaced the thermostat. I can't get the codes cleared out for some reason