So my issue is, when i purchased the truck few years back it did not have a check engine light. So we thought everything was okay. We later found out when trying to get the emissions done that it failed because they couldn't read the system. If you stop at the store and turn the vehicle off but leave the key in the run position for a few seconds to a minute and try to restart the truck the check engine light will then be on and stay on until we turn the truck completely off and remove the keys for a few minutes. What would cause this to happen? Is it like a radio where it has a power wire and a memory wire which saves your stations when you shut the vehicle off? And any idea on how to fix it?