How do you reset the pcm on a 2008 Mazda 3 after it was reconected?

To reset the PCM (Powertrain Control Module) on a 2008 Mazda 3 after it has been reconnected, disconnect the negative battery terminal and leave it disconnected for about 15 minutes. This allows the PCM to clear any stored codes and reset its memory. Afterward, reconnect the negative battery terminal and start the vehicle, allowing it to idle for a few minutes to recalibrate the system. Always ensure that you have the radio code if applicable, as this process may reset it.