Once you have done this if you still really want to remove the jailbreak then download the 4.84 OFW and install it the same way as the REBUG PUP file. If it says you need to dump your EID_root _key when you select " Re-write Target-ID in Flash " then the EID_root_key has failed to dump correctly or the Toolbox cannot find it and you should try dumping it again. If " Target-ID " still says DEX then the console is still DEX. which will be on the last column scolling left.
Now your PS3 should reboot again and when it does you should be converted back to CEX, to check this you can go back into REBUG Toolbox and find " System Information".
On a FAT32 MBR format USB Drive create a folder called PS3, then in that folder make another one called UPDATE then put the downloaded PUP file in here and make sure its labled PS3UPDAT.PUP.
It will download a ZIP file and in that ZIP will be a TXT file with a URL in, copy and paste that URL into your Browsers address bar and when you hit enter it should start to download the PUP file> Don't use Broswers like MS IE, or MS EDGE to do this as they have a habbit of not downloading the PUP and dispalying gibberish. The latest REBUG is 4.84.2 and can be found here: Put the new HDD in then download and install a REBUG D-REX CFW not REX. This is what my CECH2003A show everytime as it too has been converted to DEX. Click to expand.If its asking for v2.70 then this PS3 is an original CECH2000A and it has been converted from CEX to DEX using REBUG.