IBM PCjr Hardware Maintenance And Service page 212

1. Set the system unit's Power switch to Off.
2. Unplug the parallel printer attachment wrap plug
from the parallel printer attachment.
3. Plug the printer cable into the parallel printer
attachment.
4. Set the system unit's Power switch to On.
5. Set the graphics printer's Power switch to ON.
6. Bring the advanced-test menu to your display
screen.
7. Move your cursor to ID "A" under the graphics
printer symbol.
8. Press the Enter key.