With key on, push off and warmer on the climate panel until all segments illuminate. It will display all codes and return to ECM. With the fan down button, scroll to ACM, or ACP, and then push fan up to select. From there you can scroll through options like data, inputs/outputs, overrides, codes, and clear codes. When you get the selection to clear codes, push fan up, and you should be done. You can shut key off to exit, or push either auto/econ or the recirc button to exit with key on.