If you have Syswin or CX-Programmer software and the correct interface cable, you will be able to read what the error is in the software.
You cannot clear a fatal error if it is current, but if you know what the error is (from the above) it will allow you to fix the problem and then you can clear the error.
It is also possible with a hand held programmer, just more difficult.
Do you have the software and interface cable to read what the error is? If so, what error does the software report?