printer says 'paper jam' but i've checked everywhere and there's no paper stuck, brother mfc-j4335dw

Diagnosis

The "Paper Jam" error on the Brother MFC-J4335DW is frequently a "ghost jam," where the mechanical sensors are triggered even though no full sheet of paper is obstructing the path. This occurs because the printer relies on small, plastic "actuator flags" (tiny levers) that are pushed aside as paper passes through. If a tiny scrap of paper—sometimes as small as a confetti flake—gets lodged behind one of these flags, the lever remains in the "active" position, tricking the logic board into thinking a jam exists. Another common cause is a buildup of paper dust or a shifted piece of the internal plastic guide that has pushed a sensor out of alignment. Because the MFC-J4335DW uses a high-speed inkjet feed, a single misfeed can tear a small strip of paper off the edge of a page, which then slides deep into the chassis, far beyond the visible areas of the paper tray or the output slot. To confirm this is a sensor issue and not a physical blockage, try to initiate a "Reset" by power-cycling; if the error reappears instantly before the carriage even moves, a sensor flag is stuck.

How to Fix It

Follow these precise steps to clear the hidden sensors and reset the feed mechanism:

1. Power off the device and disconnect the AC power cord from the wall outlet. This is critical to prevent electrical shorts when probing the interior.
2. Open the rear jam clear cover (the hinged door on the back of the machine). Use a high-lumen LED flashlight to inspect the rollers. Look specifically for tiny white fragments of paper lodged in the gap between the rubber rollers and the plastic chassis.
3. Remove the paper tray completely. Reach your hand into the tray slot and feel for any curled scraps of paper at the very back of the feed area.
4. Lift the scanner unit (the entire top assembly) and prop it open. Locate the print head carriage. Gently slide the carriage to the far left or right to clear the center of the paper path. Look for any torn pieces of paper resting on the black plastic strips (encoder strips) or jammed in the star-wheels.
5. Check the "Duplex" area. If you were printing double-sided, open the rear cover and gently push the rollers in the opposite direction of the paper flow to dislodge any hidden fragments.
6. Clean the sensor flags: Use a can of compressed air to blow sharply into the paper path, specifically targeting the rear entrance and the output slot. This often knocks loose the tiny scraps that are holding the actuator flags down.
7. Reconnect power and perform a "Hard Reset": Hold the power button for 5 seconds while plugging the cord back in to clear the volatile memory.

If That Didn't Work

• Manual Sensor Reset: With the scanner unit open, locate the small plastic levers (flags) along the paper path. Use a cotton swab or a thin plastic probe to gently flick each lever. They should snap back into place with a slight spring tension. If one feels "mushy" or stuck, there is debris behind it that must be removed with tweezers.
• Roller Cleaning: The "Paper Jam" error can actually be triggered by "slippage." If the pick-up rollers are glazed with paper dust, the printer thinks there is a jam because the paper isn't moving at the expected speed. Dampen a lint-free cloth with isopropyl alcohol and wipe the rubber rollers in the paper tray area until they regain their grip.
• Firmware Refresh: Occasionally, a glitch in the MFC-J4335DW firmware causes false positives. Connect the printer to your PC via USB and use the Brother Firmware Update Tool to ensure you are on the latest version, as some updates specifically address sensor sensitivity.
• Internal Chassis Check: If you are comfortable, remove the rear cover screws to gain deeper access to the duplex tray. Check for any foreign objects (like staples or paper clips) that may have fallen into the machine and are preventing the sensor from resetting.

Heads Up

• Never use metal tweezers or screwdrivers to pull paper out of the machine, as scratching the plastic feed guides or tearing the encoder strip will cause permanent print alignment issues.
• Avoid using "cheap" or ultra-thin paper (below 20lb/75gsm), as this model is prone to "curling" which triggers false jam errors.
• Do not use oil or lubricants on the rollers to fix feed issues; this will attract dust and cause the rollers to slip, leading to more frequent jam errors.
• Always pull jammed paper in the direction of the paper path (forward) rather than backward to avoid damaging the delicate sensor flags.