P0720
 

I replaced countershaft SPeed Sensor in it and it still came on. I also used a modis and cleared the code, still same.

Any other ideas? ALl I had was P0720 & P0700. I know 700 is general trans fault as a result of 720.

That code often means the trans is shot. If that code came up on pilots, accords, and odyssey's we almost always replaced the transmission. Rarely would this code appear on civics though.

I can't see how that would be the case. Vehicle has 83k on the trans, always serviced at Honda Dealer. The engine had loose main bearing, pulled it out, rebuilt. Trans wasn't touched, Torque Converter never taken off.

Upon reinstalling, filled with genuine Honda ATF.

I know the trans isn't toast.

A lot of the p0700-p0720 codes that point you toward incorrect speed at sensors or malfunction often have nothing to do with the sensors on hondas. Most actually indicate slippage in the trans, incorrect gear ratio- input/ output speed malfunction codes are most commonly codes that are associated with replacement in a dealership setting. The exceptions are - the car was in an accident, code sets immediately after clearing code (is this your case), or major work was just performed (soft set connector, damaged wiring ect.)