Most likely your crack is letting too much air into your exhaust, and when your o2 sensor reads it, it is spiked off the charts lean. The computer says that can't be right and throws the circuit code, not the lean code. Thats my thoughts anyhow, I could be wrong. Start there, it will need to be fixed anyhow.
“Coming of age in a fascist police state will not be a barrel of fun for anybody, much less for people like me, who are not inclined to suffer Nazis gladly and feel only contempt for the cowardly flag-suckers who would gladly give up their outdated freedom to live for the mess of pottage they have been conned into believing will be freedom from fear.”