1999. Where can I get a diagram of front seat recline mechanism?

If the rear seat of your 2004 Mitsubishi Endeavor is not reclining, there are a few potential causes to consider:

1. Broken recline mechanism: The recline mechanism, which is located under the seat, may be broken or damaged, preventing the seat from reclining. You can try to manually operate the recline mechanism to see if it is working properly.
2. Obstruction: There may be an obstruction, such as a foreign object or a piece of debris, preventing the seat from reclining. Check under the seat for any visible obstructions.
3. Wiring issue: There may be a problem with the wiring or electrical system that is preventing the seat from reclining. Check the wiring under the seat for any visible damage or loose connections.
4. Fuse issue: The fuse for the seat recline function may be blown, causing the seat to stop working. Check the fuse box in your vehicle to see if the seat recline fuse needs to be replaced.

If you are unable to identify the cause of the problem and the seat is still not reclining, it is recommended to bring your vehicle to a mechanic or a dealership for further diagnosis and repair.

open your browser type in you query and check articles that appear you might even get it in PDF format .

remove seat(s) and check for obstruction in the mechanism path. You'll need a big Torx bit.

to determine if lever just broke and seat works OK, actuate seat with vice grips to verify operation

I wouldn't ruin anything by trying things yourself

I would have a dealer check it out

The dealer I used in the past, has a seat specialist come
in on Wed only, around 5:30 after the service bays close
& one service writer hangs out until that person fixes a
couple vehicles seat issues

2010 Equinox drivers side won't recline.
Found the cable popped off recline mechanism.
Pulled back the lower seat panel near the recline lever after removing one torque screw located on said panel which is on the back of seat. Works great now. By the way, Freedom Chevrolet in San Antonio, Tx, without diagnosis, wanted to charge my girl friend $860 to replace the whole assembly.

On W-Body vehicles, the front seats are secured to the floorpan by two front hook attachments and two rear bolts installed to nuts welded to the floorpan.
The manually operated two-way front adjusters provides only fore and aft movement of the seat. When the seat adjuster handle located on the front seat is pulled up, the seat adjusters unlock, permitting travel of the seat. When the seat is in the desired position and the seat adjuster handle is released, the seat locks in place.
A power operated six-way seat adjuster is available. The adjusters are activated by three 12 volt, reversible, permanent magnet motors with a built-in circuit breaker. The motors are energized by a switch bolted on the seat side panel.
The three motors drive the front seat and rear vertical actuators and a horizontal actuator. When the adjusters reach the limit of travel, torque is absorbed through the rubber mounted grommets located between the motor and the support. An overload relay is provided in the circuit and will open should excessive stall be applied.
The optional 60/40 split bench front seats have seat back head restraints on the driver's and passenger's seat back. The head restraints are designed so they cannot be removed from the seat back without first inserting a small rounded tool inside the head restraint support tube to release the locking tab. The 60/40 split bench seat is equipped with a reclining mechanism on both the driver's and passenger's side. The recliner lever is located on the outboard side of the spring cushion. When the lever is pulled upward, the spring loaded dual linear reclining unit located in the cushion frame is released, allowing the seat back to be pushed rearward or allowing the spring loaded reclining unit to bring the seat back forward.
Bucket seats are equipped with manual reclining mechanisms. An optional six-way power seat adjuster is available. Some bucket seats are equipped with inertia seat back locks. This system allows the seat back to fold forward without requiring the occupant to release a locking lever or access to the rear seat area. During a sudden stop or deceleration, or if the front of the vehicle is nose down, the inertia system of the seat back lock will engage, holding the seat back in its rest position. A release lever is provided to allow manual release of the seat back lock when the vehicle is in the nose down position. The release lever is located at the lower rear outboard corner of the seat back.
Some W-Body vehicles (notably Pontiac coupes) have passenger front seats equipped with an E-Z Entry device. This is actuated, in an unoccupied seat, by completely folding the seat back forward disengaging the adjuster, and sliding the front seat forward to gain access to the rear seat area. To return the seat to its normal position, return the seat back to its rest position, and slide the entire seat rearward, engaging the adjuster.
W-Body rear seats are available in several styles including a rear seat with an integral child restraint device.

well lets not start with visegips .
the lever needs to be removed by removing the screw and removing the lever.
go to the dealer to get the new lever and put it on.

Use some penetrating lubricant on all pivot points and levers around the recline mechanism, and let the lubricant sit overnight. In the morning, try to work the recline mechanism free. (The vehicle is quite old at this point, and likely parts in the interior need lubrication. These parts should be lubricated annually.)