Hp MFP 178nw how to reset counter, how to enter tech or service mode, how to enter pass code

press in this buttons 2.back 3.left arrow 4.right arrow 5.ok 6.stop enter pass code - 1934 1.press right arrow key one time displaying number 1, then press ok button 2.press left arrow key two times, displaying number 9, then press ok button 3.press right arrow key 3 times displaying number 3 then press ok button 4.press right arrow key 4 times displaying number 4 then press ok button two times finely switch OFF ON the machine