How do you clean trane Air conditioning drain lines?

If you're referring to drain lines coming from the drip pan beneath the air handler (the one inside the house), then just take some bleach water and pour it in the drip pan and it'll flow down the pipe and clean.

If you're referring to another drain line coming from the machine itself, go ahead and cut off the pipe and replace it with a new pipe. Make sure you know what you're doing. It's PVC pipe, so use appropriate PVC glue and elbow joints.

For best results, call your installation professional.