We had a a frustrating day with the autosteer on our 2011 Magnum 290.  The tractor was in the shop last fall because a bunch of seals failed on the front end.  We used it for a few days last fall but only with the scraper and did not use autosteer.  Today we started some discing and on the very first past found that the autosteer would engage and then promptly steer the tractor offline until it disengaged.  After many calls to the dealer (who installed the system) and a Trimble dealer that we used for almost all our other precision stuff we narrowed the problem down to the steering sensor.  When the front end was reassembled the hex rod/bolt that the steering pot sets on was not indexed properly.  Because of this the FMX was not seeing enough voltage between full left and straight and was unable to calibrate the sensor.  I was able to re-index the sensor and get it calibrated but it sure wasted my day!  Once I learned how the entire system worked getting it adjusted properly was not too difficult.