Oki ES3640MFP Service & Troubleshooting Manual page 86

400: Paper Size Error / 401: Multiple sheet feed error
Condition
Error indicating that the detected size is not the specified size. The printer ejects the paper, then, displays the error.
* Error 401 may occur along with Error 400 when the paper is fed from the tray.
Cause
There are several possible causes for this problem.
1. Hopping roller or Registration roller cannot transport paper because they have become dirty with paper dust, etc.
2. A piece of paper, foreign substance, etc., has got stuck in the IN1 or IN2 sensor lever.
3. IN1 or IN2 sensor motion failure.
4. Sheets are sent stuck together due to large friction (due to static charge, etc) (Multi feeding).
How to remove the jammed paper
1. If Error 400 or 401 occurs by itself, paper is ejected. So there's no need to remove the paper. Open/close the top cover.
Check Points
Frequent Error 400/401
tray's HP rollers, see Error 390.
Open the tray1 side cover and the side cover, and check the following areas and clean them.
edges, then, set them in the tray.
Pull out the tray - Open the side cover - Clean or replace the rollers.
Remove the tray and clean / replace the hopping rollers (3). For instruction on how to clean MP
Check to ensure the paper guides of the tray are correctly set (if it matches the paper size).
Fan paper well and align the
Check Paper Guides
Jam indication though there seems
to be no jammed paper:
Check for a piece of paper or
foreign substance in the IN1 or 2
sensor.
Check if the IN1 or 2 sensor arm
moves up and down smoothly.
Frequent Jams:
Check the registration roller and
clean thoroughly.
Check for a piece of paper or
foreign substance in the paper path.