Perform the following steps:

1. Print a configuration page.
2. If the Duplex Tray is properly installed, the configuration page will read Duplex Unit: Installed under Installed Options. If the configuration page shows Duplex Unit: Not Installed, check the lower inverter wiring harness:
1. Turn the printer off and unplug the printer.
2. Remove the access cover that is found under the power cord on the right side of the printer.
3. The lower inverter wiring harness (15.7 KB) is a series of gray wires connected to a white connector.
4. With both hands, put your thumbs on the outside of the left and right edges of the connector and push firmly on the connector to ensure that it is seated properly.
5. Reconnect the power cord to the printer.
6. Turn the printer back on and print another Configuration Page after the printer has warmed up to ensure that the Duplex Unit is shown as Installed.