You can get a service manual for your Rancher HERE
I recommend that you pull apart every harness plug and make sure each are clean and dry before you go any further. If any are wet spray them out with some electrical contact cleaner or better yet, buy a can of CorrosionX. Then snap them back together with some dielectric grease in the plugs to make them watertight.
Most electrical problems on ATVs stem from them getting wet... despite what you may expect, they are NOT ready for water and mud when they leave the dealer.
If your DTC code still remains after performing these routine services, use the service manual troubleshooting steps (in the back of the manual there is an entire section dedicated to DTC fault diagnosis) to troubleshoot and isolate the fault. As I mentioned, there may be nothing wrong with it except for a dirty/poor wiring harness connection.
Enjoy your work!