scans come out with black streaks or lines down the page every time.

Diagnosis

The presence of consistent vertical black lines or streaks on your HP LaserJet Pro MFP M227fdw scans is almost always a result of physical contamination on the scanning optics. This happens because the printer utilizes two separate scanning paths: the large flatbed glass for manual placements and a narrow strip of glass for the Automatic Document Feeder (ADF). When a tiny speck of dust, a smudge of ink, or a piece of correction fluid (White-Out) adheres to the glass, the scanner sensor reads that debris as a solid black object. Because the paper moves continuously across the narrow ADF glass strip, any single point of contamination is "dragged" across the entire length of the digital image, resulting in a continuous line from top to bottom. You can confirm the source of the problem by comparing a scan made via the flatbed (lifting the lid) versus a scan made via the ADF. If the lines only appear when using the ADF, the narrow strip of glass is the culprit. If they appear on both, the main platen glass requires cleaning.

How to Fix It

To eliminate these streaks, you must perform a deep clean of the optical path using a non-abrasive method to avoid scratching the glass, which would cause permanent lines.

1. Power down the M227fdw and unplug the power cord to prevent any electrical surges during cleaning.
2. Lift the document cover to expose the main platen glass. Locate the narrow, rectangular strip of glass situated to the left of the main large bed. This is the ADF scanning glass.
3. Dampen a lint-free microfiber cloth with a small amount of 70% isopropyl alcohol or a dedicated glass cleaner. Do not spray the liquid directly onto the glass; spray the cloth first to prevent liquid from seeping into the chassis.
4. Wipe the narrow ADF glass strip firmly from left to right. Pay special attention to the edges where the glass meets the plastic frame, as dust often accumulates in these crevices.
5. Inspect the glass under a bright light or flashlight. Look for "invisible" residue like clear tape adhesive or dried glue. If you see a stubborn speck, use a cotton swab dipped in alcohol to gently scrub the specific spot.
6. Clean the main flatbed glass using the same method, ensuring no streaks are left behind.
7. Close the cover and plug the unit back in. Run a test scan using a blank white sheet of paper through the ADF to verify the lines are gone.

If That Didn't Work

• Inspect the ADF rollers for debris. If a small piece of torn paper or a staple is caught in the feeder mechanism, it can occasionally cause the paper to shift or drag, creating artifacts that look like streaks. Use a can of compressed air to blow out the feeder path.
• Check the underside of the white plastic calibration strip (the white bar that sits directly opposite the narrow glass strip). If this plastic is stained, scratched, or dirty, the scanner may misinterpret the white balance, creating gray or black bands across the page. Clean this plastic strip with a damp cloth.
• Perform a hard power reset. Unplug the power cord from the back of the printer while it is still turned on. Wait 60 seconds, then plug it back in. This clears the temporary memory and resets the scanner lamp calibration.
• Update the firmware via the HP Smart app or the printer's web interface. In rare cases, "streaks" can be a digital artifact caused by an outdated image processing driver failing to communicate correctly with the CIS (Contact Image Sensor).

Heads Up

• Never use paper towels or tissues on the scanner glass; these are abrasive and can create microscopic scratches that permanently result in thin white or black lines.
• Avoid using ammonia-based cleaners or acetone, as these can strip the protective coating off the glass and cloud the optics over time.
• Always check your original documents for "bleed-through" or ink smears before feeding them into the ADF, as one messy page can contaminate the glass for every subsequent scan.
• If you use correction tape or liquid White-Out, allow it to dry completely for at least 2 minutes before scanning to prevent the residue from sticking to the ADF glass.