Cant clear ECU codes

[dwd1985]

I have cleared my ECU codes before, like after I replaced knock sensor #2, but for some reason, my current codes will not go away. I have codes 22, 34, and 37. Each time a new code appeared, all that happened was the CEL came on for a few seconds, and then went out. It doesnt ever come on anymore, and that is why I want to clear the codes. I havent done anything to fix these problems yet, but I thought that maybe 1 or 2 of these codes could possibly have been thrown by mistake, like my knock sensor code (22) could have been caused on the night I overheated, and not actually been a bad knock sensor. So I wanted to clear the codes, and then wait for the CEL to come on again to see what really did need to be fixed, and what was just an accident. But so far, it is impossible to clear the codes. Everytime I do the procedure (which I know that im doing properly), and then plug in the wire again to make sure the codes are clear, they pop right back up. Does this mean that all 3 of these things are actually bad?