All Pioneer receivers whose model numbers begin with "DEH" have a reset button located inside the faceplate of the unit. When the reset button is pressed, it will completely reset the unit, restoring all settings to their factory defaults. Pioneer recommends resetting the unit when it is first installed if you are experiencing any errors with the unit or if strange messages appear on the display.
Press the release button on the front of the radio the drop the front panel, then remove the front panel by pulling it away from the unit.
Locate the reset button, which is a tiny button labelled "Reset."
Push the reset button using the pointed instrument to reset the unit.
Replace the front panel by inserting the left side into the unit first, then pressing the front panel into place.