U99 is a general communication failure between processor and timer, and there may be different causes. Common cause is a defective disk. Removing disk from the drive sometimes may fix the problem.
The first reset that you can attempt is disconnecting power for two minutes.
I quote below a post that was originally published in the MyCe forum (here
"According to the service manual the U99 error is specifically a "hang
up" displayed when there is a communication error that has occured
between the main microprocessor and the timer microprocessor.
With more than twenty Panasonics (including four DMR-ES15 models) I'll offer my own observations:
There can be any number of causes for the U99 error, including a
culmination of reading, writing, finalizing errors--sometimes appearing
after U61 or U88 reading errors. The U99 error might also be associated
with unusual DVD Drive noises, "grinding" indicating a dirty rubber hub
and spindle; "clunking," "chugging" or "errrp" noises indicating a dirty
lens or a failed laser assembly (the "optical pick-up").
Initial remedial measures include the routine DVD Drive lens, rubber hub
and spindle area cleaning described in other CDFreaks/MyCE and AVS
Forum threads. If that does not correct the problem(s) laser assembly or
DVD Drive swapping with a direct replacement may be indicated. Also
check for a disturbance to a ribbon cable or ribbon cable contact,
correct or repair as necessary.
If the Digital PCB has become problematic, model-specific replacement is
indicated. If the DVD Drive on-board contoller (if so equipped) has
become problematic, model-specific replacement is indicated. In most
cases "model-specific" means the same model year DVD Drive and, with
problematic Digital PCBs or DVD Drive controller boards, replacements
should be from the same model year and the same or very similar model
recorder. Laser assemblies should only be replaced with the same model,
i.e., 3331A and 3332A "optical pick-ups" might not interchange
The U99 error may also be displayed when inferior media is in use.
(Beginning in 2008 I've used nothing but Taiyo Yuden 8x Premium Line
DVD-R media in my Panasonic, Philips and Magnavox DVD Recorders and
The U99 error may also be displayed when there is an operating system
"time out" occasioned when the user attempts to move too quickly between
digital and analog channels (in 2007 and newer EZ series models)."