If you have a back molar tooth ache does that mean root canal if the tooth is crowned?

Depends on what’s actually happening, I think. I have had some temporary tooth aches (not very bad ones though) that didn’t mean anything and went away. But the dentists I’ve know have said that tooth pain is an emergency, as a rule, so I’d call one and let them have a look. If the pain’s bad, I’d call immediately. If it’s minor, I’d wait till they open on Monday morning, and hope it goes away before then and/or take some pain reliever.

It could just be decay that needs to be dealt with. It could be a root canal is needed. As @Zaku says, call your dentist and get in as soon as possible.

PS: If it’s a throbbing pain, particularly one that gets worse when you lay down, that usually means a root canal is coming your way. A heat pack help with that.

Do not discount that maybe if not the actual tooth , but jaw infection.

Maybe. Most likely (from my own experiences) your crown seal has been broken and bacteria has made it’s way underneath your crown. If the tooth is not dead and there is surface enough for a filling and replacing the crown, that might be what your dentist suggests. I would let her or him know that I don’t expect to have to buy another crown. In any case, if your present crown is not damaged you should be able to keep it after the tooth itself is healed. They often try to sell y ou a new crown…...............why wouldn’t they?