Problem with our printer 5200tn ...error 49 4c02

From the Service Manual:

49.XXXXX ERROR
alternates with
To continue turn off then on
A critical firmware error has occurred that
caused the processor on the formatter to
abort operation. This type of error can be
caused by invalid print commands, corrupt
data, or invalid operations. In some cases,
electrical noise in the cable can corrupt data
during transmission to the printer. Other
causes include poor-quality parallel cable,
poor connections, or home-grown programs.
On rare occasions, the formatter is at fault
which typically appears as a 79 Service Error.

1. Turn the printer off and then on.
2. Press Stop to clear all print jobs from the printer memory.
3. Turn the printer off and then on.
4. Try printing a job using a different software program. If the job prints, try using the original software program to print a different job.