firstly it wont be steering 'rack' its column , secondly you MUST make sure your battery is 100% good before replacing anything as it could be down to battery, did it come on after starting or when heater fans and lights are on, or did it come on after hitting a pot hole or putting it on full lock.
there is hundreds of pages about this on net, if its not your battery it will be motor or steering ECU , I only sell full columns as this covers all bases and is easy to swap, if you are fairly mech minded, full column from me is £90 delivered but you will need to know your 4 digit code from the steering ecu
but first make sure your battery is ok, when was the battery last changed?