We had a customer trying to figure out a 13.A2.FF error in an HP M60x series, also gave a 13.FF.FF error. The 13.A2.FF error code isn't listed in the service manual, other sites suggest paper or dust blocking a paper sensor -- guess what is was?

Bad toner cartridge.

Goes to show, always try a different toner first, especially with these weird errors. It's really quick to test the toner compared to removing assemblies to get at a sensor.