HP 3150 EN - Manual (Page 176)

174 Troubleshooting EN
Engine test
The engine test is used to verify that the print engine is functioning
correctly. The formatter is bypassed during an engine test, so the
engine test is useful for isolating printer problems. The engine test
prints vertical lines down the entire printable area of a page and is
also useful for checking and adjusting registration.
Engine test button location
The engine test switch is accessible without removing the covers. It is
located on the bottom of the HP LaserJet 3100/3150 product.
.
Figure 75. Engine test switch location
To print an engine test
Lift the front of the product and squeeze the engine test switch. A
single test page is printed.