Means you heater isn't functioning within set time limit. The best you can hope for is that the heater element has a break in the filament, or that the temp sensor is defective, or the heater relay is not working properly. You need someone with an electrical background to check these unless you are familiar (& comfortable) with using a multimeter...perhaps even on live components. If in doubt get help...better to part with some cash than end up in hospital...or worse. I should also add that this fault could also be caused by a defective control module, however this is less common.
Mike
October 2009