engine does not run at constant speed with Odessey on

I'd first take a look at it.  If the speed is varying, the magnet ring may just be loose.  If so, just stick some CA adhesive on it and slide it back up against the lip of the flywheel, job done.

Checked the ring and it is tight and up against the fly wheel and not slipping.  There does not appear to be any breaks in the ring.

Marty

I'd be wondering about the mechanical aspects in that case.

John - what mechanical issues would there be affected by running with Odyssey on, and not affected with it turned off?

I have a couple of TMCC locomotives with the magnet ring. I use FasTrack. Unfortunately FasTrack has terrible conductivity between the sections. There are sections with voltage drops and sections with voltage spikes. I know where the dead spots are since my AC-motored locomotives slow down at those sections with voltage drops. I have jumper wires all over the place which helps with electrical continuity but there are still dead spots that develop.  My TMCC locomotives with Odyssey slow down a bit at those dead spots. The TMCC locomotives are a bit slow to respond to the voltage drop whereas the Legacy equipped locomotives respond much more quickly and, as such, the voltage drops are not noticeable in the operation of the locomotive.   Certainly the TMCC Odyssey system smooths operation out quite a bit but the locomotives still initially slow down a bit at those dead spots. 

Thus, my question is, are there voltage drops around the track which could impair operation of your TMCC Odyssey locomotives?

There are no problems with any other locomotives; TMCC, ERR or legacy.  When I turn off Odessey it runs very smooth.  I really do not need the odessey on my layout since there are only 2 very small changes in grade.

Marty

If it runs fine without Odyssey and varies in speed with Odyssey, then it's something about the sensing.  Either the magnet ring, the spacing to the sensor, a bad sensor, or a loose connection.  Finally, it could be an issue with the Odyssey board, but most issues with the DCDS preclude any running.

Any chance the Odyssey switch could be wired backwards ?

If the switch is wired backwards, why would it be running smooth with odyssey turned off and not on?  I have to think it might be something that John alluded to like a bad sensor or loose wire.  I am going to wait until I have to service the smoke unit before opening it up.

Marty