You don't know a great deal agout how to use a VOM, but you confirmed in a round-about way that all four were fine based upon the reading you reported. I'm guessing you were on either the 100K resistance scale or the 1 meg scale. Either way, you tested fine.
Do I understand correctly that *someone* diagnosed sensor as bad and then cleaned wheel and now all is fine? Are we saying BMW replaced a good sensor?
Someone said they don't believe you can diagnose a bad module. You can. You just can't tell a bad input from a bad module. You can diagnose a faulty module that won't communicate with the other modules/DMS for example. Just not a bad sensor from a bad module.