Canít see which unit have. LF jack error implies an error with the left front jack as opposed to a rear jack. As to the rear jacks - make sure you have sufficient voltage from either good batteries(battery) or shore power. Iíve read where insufficient power can cause some odd errors. Next, Iíd check the electrical connections at the rear jacks and also where they plug into the control box. Lastly, if it is indeed this system, you can pull the rubber plug on top of the jack and operate them manually if thereís room.
Thatís all Iíve got. The smart people should respond soon.