The tailgate on our 1998 (post-update), XJ Cherokee would not unlock. The normal thumping noise could be heard when the tailgate remote lock/unlock solenoid operated but the tailgate would not open. The key appeared to turn normally in the tailgate lock but the tailgate could not be opened.
Searching the intertubes showed that tailgate lock and latch failures were a known issue with the XJ Cherokee. Further seaching located the factory service manual but that was useless as it assumed any tailgate servicing or repair work would start with the tailgate open. Our problem was the tailgate would not open.
Online I could only find instructions for the pre-update XJ Cherokee model and that was not really relevant for the post-update model. Up to the 1997 update model the XJ Cherokee had a fibreglass (of course for Americans this is spelt fiberglass) tailgate exterior with an interior plastic cover. The post-update XJ Cherokee have a metal tailgate exterior with a larger, different shaped plastic interior cover. The pre-update instructions seem to start with removal of all screws that attach the interior plastic cover to the tailgate. This is not possible on the post-update XJ Cherokee as the four lowest screws located beside the window glass are obscured by the bodywork when the tailgate is closed. The accessible screws are on the roof end of the plastic cover and removing them will achieve nothing when the tailgate is shut. They do have to be removed at a later stage so removing them out of order isn't an issue.
Catch 22, you have to open the tailgate to remove the cargo barrier in order to open the tailgate. Step one, pray that you haven't installed a cargo barrier. Guessing a cargo barrier jammed against the spare tire mounted in the cargo area is going to be even more difficult. Didn't have our cargo barrier installed when the tailgate latch release mechanism failed so missed out on the full catastrophe. Murphy's law failed to have full effect in this instance. The procedure below assumes you have access to the tailgate's interior cover. You have get to get past the cargo barrier before you can start on opening the tailgate but the mounting bolts for a floor to ceiling cargo barrier are within the cargo area. In other words Catch 22.
The following assumes no cargo barrier.
The tailgate latch is designed to be a burstproof lock and will resist attempts to force it open. The locking mechanism passes through the center of the striker plate and totally encloses the rear of the striker plate. The tailgate, plastic moulding and lock mechanism enclose the striker and this restricts access. I couldn't release the catch by leavering with a screwdriver. With more knowledge or experience it maybe possible to release the lock with a screwdriver or similar tool. I don't have the answer. So my next attempt was to directly manipulate latch mechanism to release the tailgate.
The inside plastic cover is attached by a combination of screws, the grab handle and what look like nylon or some other type of plastic clips. The plastic clips are a push fit and designed to pull away from their holes in the metal tailgate.
Main issues are the plastic clips can remain attached to the metal tailgate then break the molded mounting lugs on the interior plastic cover, plus they make a horrible, 'breaking plastic' type of noise when being pulled from the metal tailgate. By gently pulling on the centre of the interior plastic cover at the base of the window glass it is possible to release the two centre plastic clips then create enough gap to slide your hand into the area of the tailgate lock. The noise created as you release the plastic clips just has to be ignored, only create the narrowest gap for a hand so you don't distort the cover. All you can do is hope nothing is damaged or breaks.
From the broken lug I discovered after removing the inner plactic cover the previous owner probably had a tailgate problem and there had been an unsuccessful fix. As you can see from the photo the centre of the lug just breaks out.
Just above and to the right of the striker plate, at the level of the key lock there is a vertical, 5mm diameter rod. Pulling the rod up will release the tailgate. The rod had become detached from the lock and this prevented the tailgate from being released.
Once the tailgate is open, remove the grab rail by extracting the two plastic plugs with a flat bladed screwdriver then you can remove the long Allen head screws. The positioning of the plug in this photo is probably wrong and the plugs should be extracted in the same orientation as the screws.
Remove all the interior plastic cover's screws along the top and sides of the glass window. Remove the interior plastic cover by carefully releasing the remaining plastic clips.
Examination of the plastic cover revealed the previous owner had broken a couple of the mounting lug so likely this was not a new fault. Pushing the rod back into its clip restored normal lock operation but was not guaranteed to provide a permanent fix.
The clip appeared to be so worn that the rod could pull through the clip, plus the metal seemed to have lost its 'spring' therefore the clip could fail to securely hold the rod into the clip. The clip is riveted onto a lever and is not sold as a spare part. Replacing the lock mechanism would be an expensive fix so other options were investigated.
The lever only lifts the vertical rod. By placing a cap on the rod it could securely hold the rod into the clip and the vertical movement of the lever could release the lock. The vertical rod does not have a thread just concentric ridges, so you can't 'thread' on a nut to act as a cap. Purchased a couple of shaft collars (5mm internal diameter with a grub screw) from a local bearing supplier. There are different types of shaft collar (e.g. split collars) but this repair only needs the simplest type. There were two wholesale sources in Australia for this size of shaft collar but only one of them held stocks. To ensure the cap would be secure two collars were used and Loctite applied to the grub screws to ensure vibration could not loosen the grub screws.
A cap was cut from a length of 20mm aluminium rectangular channel and a 5mm hole was drilled in the centre. 16mm channel was tried but it was too narrow to fit over the clip and lever.