HP PCL/PJL reference - Printer Job Language Technical Reference Manual

2-10 PJL Command Syntax and Format EN
Note Any errors that occur during PJL parsing can be received by enabling
device status as described in Chapter 7 (send the @PJL USTATUS
DEVICE = VERBOSE command). Appendix D lists the status codes
that are received by the host when an invalid command is received
and unsolicited verbose device status is enabled.