I have a 2010 SD 310 with the Axius joystick. When it works, it is great. But, it has been the source of many headaches and pricey marina repairs. I'm not sure how to clear your alarm, but I've found that Mercury technical support is very helpful. I think you can reach them at 920-929-5040. They are Central Time.
Make sure when starting the the motors you alway turn on the starboard key first then port key. Then always start the starboard motor first, the starboard motor is the brain it tell the port what to do. When shutting everything down do the opposite shut port off first then starboard.
I've been trying to figure mine out too. I bought the vessel view mobile to try and get a handle on the code (it gives more detailed code info) but it is telling me I need a software update. In doing some online research, I found this can be the problem, also weak batteries can cause the fault.
I have a 2010 390 DA with Axius. When I first got the boat I had various issues with codes. I have posted these issues several times. First check to see if you the your joystick is the new updated version. Service bulletin 210-70. If it is the old version, replace it with the updated joystick. The updated (879365A21) version of the joystick cured all the spurious codes. Later I started to have various codes about the TVM. In the end I had to replace the engine harness. Also, both lance and kipgresio are correct about starting the engines in sequence and batteries. Mercury require batteries with high Cranking Amps. I originally installed lower (700-800 CA) and had various problems. I then went and purchased high (1100 CA) batteries and have not had any issues since. Mercury recommended, I think they were Odysseys at $400 each. I ended up trying Duracell from Sam's at $110 each and am running on 3 years with no problems. But you must get the commercial version that will have nearly 1100 CA's. I even took my handheld battery tester with me and pick out 4 of the highest CA batteries on the shelf.