I think that as Hugh has suggested, using PJL is sometimes necessary on certain devices. One way I would test this out is by using a common Windows application to generate a simple PCL output, as follows.
1. Change your printer's driver to be a generic PCL5 driver, so that you can ensure a Windows application sending a test document to the printer, will print successfully in PCL. You might for example be able to use the Windows driver for "HP LaserJet 2200 Series PCL5", which is installed already, or find a universal PCL driver.
2. Use Microsoft Word, for example, to create a very simple piece of text. Check that it can print to your printer, using the PCL driver you've selected, to prove that sending PCL via the USB connection is successful.
3. Print it again, but in the print dialogue box, tick the option "Print to File". Capture the output in a file and take a look at it, with a file editing tool, or even just notepad. You will find that it prefixes the output with PJL commands. You can replicate those commands in your own output and copy what was achieved successfully via Word.