EGR sim question

I would try unplugging the battery and retrying it. You usually have to clear the codes.

Unplug the battery.
Turn on lights
Plug battery back in.

Retest.

All the $20 plug is probably just a resistor in series.

I also have purchased one of those a while ago, and it did the exact same thing.

The seller's ad claimed that it worked for several different year vehicles. I really believe that the egr sim probably would work on a fox stang, however, I suspect that on OBDI or OBDII cars, the computer might be a little "smarter", if you will, than the earlier fox computers. I don't know this for certain, but I got the same result you did and rather quickly! The computer likely realizes that the EGR is unplugged, thus, you get a CE. That would be my best guess.

its just a fancy container that holds the resistors you could go to the store and buy resistors and do it yourself and then caulk the resistors into the connector but thats messy and a pain or spend the cash and get one of them off ebay thats got a nice pakage and just plugs in...its what i will be using when i do mine...you just need to unplug the battery and reset the codes...i have heard those work well but a lot of people think its a waste of money when you can just do the resistors yourself for like 2 dollars...but i say the ebay way is easier and cleaner and if for some reason down the road you ever wanted to put the egr back on all you have to do is unplug it as apposed to digging out caulk or silicone out of the connector