Lexmark T642 takes 3 pieces of paper, doesn't print on any and gets stuck in rear door. error 250.07 Help!

SOURCE: Paper Jam

The fuser unit has a pape sensor. If, for some reason, the sensor is stuck, the printer will read a paper jam. Open the rear door and inspect the paper sensor located in the fuser assembly. See if it came out of it's original position or if there is something blocking it from moving freely. Good luck.

SOURCE: Lexmark error codes

Too many to list here. Try justmanuals.com, you can get the service manual for about $10.

SOURCE: Lexmark t642

I too ran into this problem. Printer is about 2-1/2 yrs old.
Using it as a network device. I updated firmware from
a Mac OS X computer on the network.

a. Uploaded the firmware by going to lexmark site.
Do this first in preparation of upgrading firmware.
Follow instructions to get firmware update.
b. power cycle the printer (turn off & unplug power from unit)
c. power printer and turn switch back ON.
happily printer stays alive long enough to upload the new
firmware update.
d. Log on to your printer via a computer on your network
Open a browser, address will be your printer's IP address
or dns name. ex: http://192.168.1.3 (note: if you password
protected the account, you will need that info)
e. Follow menu to Configure -> Update Code where you will
"browse" to the file on your local computer (ex:
LSSTN234.FLX) and then hit the FLASH button

SOURCE: Lexmark T630

Repeated, Unexplained Paper Jams With Little or No Damage to the Paper ID:ENUS5286
IMPORTANT: The printer should rest on a surface that is flat, level, and uniform. This is for safety reasons as well as for paper feed reliability. In the bottom left corner on the front of the printer, as well as on the duplexer and each paper feed option apart from the 2000-sheet feeder, there is a shaft that rotates as the main drive motor in the printer operates. The purpose of this shaft (called the Power Take Off shaft) is to turn the pass-through rollers in the option below. The Power Take Off (PTO) shaft rotates during the printer's POR as well as any time the main drive motor turns, including while paper is feeding from any source and when the toner is agitated in the cartridge.
If the printer is on an uneven or non-level surface, the PTO shaft may not make full contact with the bevel gear on the lower options.
If the printer is on a surface that is not uniform (such as a carpet or foam padding), the PTO shaft on the lowest option may catch or bind, causing the paper feed operation to slow or stop completely.
In either case, repeated and unexplained paper jams (with little or no damage to the paper) may occur. The paper jam is due to the increased amount of time it takes the paper to feed through the path because the PTO shaft is bound or caught on the surface below, or is slipping on the bevel gear.
NOTE: This is not a printer defect or failure although it may result in a broken or stripped PTO shaft.

SOURCE: Printing Issue - Lexmark T642

not a chip error but a mixing rod/pac man gear problem. either way the cartridge is bad....shaking could help as hard toner can cause the mixing rod to bind.