It means that it has failed one of the startup self-tests on the digital I/O subsystem – most likely that one of the chips failed a readback test.

If your unit is a "CE" type, with a removeable audio board, it might be worth giving the audio board connectors a splash of switch cleaner, and wiggling any socketed parts in the audio area. (At your own risk, of course).

Otherwise, it will have to go for service.