Need help with Deere 16000 WAM

[jdhicrop]

I'm having a problem with my Deere 1600 wide Area Mower. The front mower is down and functioning but both side mowers will not turn on even though they are both completely down on the ground. I am getting an error message from the ECM with a steady flashing light beside "lower front". The front mower is down, however, and running. I'm thinking a relay or sensor (or even a wire?) is bad but stumped here. Any one have a suggestion? Thanks