confused about engine codes

[backyardcustom]

Well, I finally pulled the codes of my truck. 1990 2.3l 5sp. I had never done this before so when I pulled the codes i got 21, for engine coolant sensor, which i expected and then I got 33, for egr, but i got the same code twice. I did it several times and got the code twice. It was key on engine off. Why did i get the same codes twice? Also, I forgot to disconnect the jumper wire and was driving around with it plugged in and my truck ran much better at idle and during acceleration. I was going to leave it like that but I hoped someone here would know why it did that. As of now its disconnected. Thanks, Jason

 

[Dave R]

If I'm understanding your question correctly, you get the same codes twice so that you can be sure that you got the codes correct.

No clue why it should have run better with a jumper wire on it.

 

[backyardcustom]

I only got the second code twice. Why wouldn't it read both codes twice. I reicieved three seperate codes but the last 2 were identical.