How can I replace a flame sensor in a Trane heating unit?

Why do you want to replace it?

Our heat was not working... it was turning on and shutting right back off. I had someone out here to look at it yesterday and they told me it was the flame sensor. He got it working and then it stopped. I can't get someone back out until Wednesday and wanted to know if I could change it myself instead of waiting. Could it be something else that is wrong?

Did he clean it? How? Most of the time they don't go bad they just get dirty.

He said he cleaned the inside but it's still not working. Can I clean it myself?

How can I replace a flame sensor in a Trane heating unit?
Very few flame sensors go bad. Scrape it with a knife and give it a try. Don't use sand paper