HP LaserJet 4 Service Manual - Page 247

PC Empty Sensor (PS2) Functional Check 1 Power on the printer with the PC tray (Tray 2) empty. 2 After the 05 SELF TEST and the 02 WARMING UP cycles, the PC LOAD LETTER (or A4) or TRAY 2 EMPTY message appears. 3 Add paper to the PC tray and re-install the tray. 4 The display should read 02 WARMING UP, then 00 READY. If the PC LOAD or TRAY 2 EMPTY message persists, replace PS2. PS4 Check (MP Tray Empty Sensor) 1 With the printer powered ON and 00 READY displayed, select the Config Menu from the Control Panel. 2 Configure the MP Tray (Tray 1) as a cassette (MP TRAY=CASS or TRAY 1=CASSETTE). 3 Lock out the remaining paper trays (LOCK= PC LC or LOCK TRAY= 2 3). 4 Remove any paper from the MP Tray (Tray 1). The printer should display an MP LOAD [paper size] message. For the LaserJet 5 printer, run a Self Test to generate the TRAY 1 LOAD message. 5 Insert paper into the MP Tray (Tray 1). If the MP LOAD (TRAY 1 LOAD) message persists (or if the load message never occurred), PS4 or the sensor flag is defective. Troubleshooting 7-17