The Nissan Path

I love my Pathfinder. Got from 21 to 32 mpg until I took it into the dealer for tire pressure warning and oil change. They hooked it up to the computer and it’s starting to feel like Windows updates. Now I’m doing as low as 10 mpg around town and never above 21 mpg. I am desperate to reset the ECM to the factory settings when I bought it. The instructions they have on YouTube don’t work with the push button start. Wondering if unplugging the ECM relay will help reset it or if it’s all stored in an EPROM somewhere. Not even sure how to remove the relay without breaking it.

If they reprogrammed the ECM with updated software, there is nothing you can do. The only way to go back to the old program is to have the ECM reprogrammed to the previous software program. To have the ECM go back to the base settings, you can disconnect the battery for a period, but this may erase the idle air volume memory and an idle air volume relearn may be needed afterwards.

How can I prevent it from being reverted without my permission every time they do the nitrogen for my tires?

don't take it to the stealer...

sounds like they put it in limp mode by accident Id take it back and make them fix it thats too much of a drop, stealerships are known for sneaky roach methods like this to get you to bring it back in