Volvo FM fault code

I have a FM 8X4 2014 with U30004B fault code its in the RCIOM rear chassis module, on the dash it says stop vehicle electrical fault loss of functionality. The only thing not working is the side markers both sides, if I take the plug out and power them they work. Any ideas on the code?

hi, did you fix it? i’m getting the same thing on a renault t range.