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Putting this here in the hopes it helps someone else out...
Last few days, my sunroof top would not close all the way, and when stowing the convertible top all the way down, it would not lock. You'll note that when stowing the top, the sunroof slides forward at the very end of the sequence to lock into position, so those two problems likely have the same cause. Eventuall, the top would not operate at all and when I tried to open it, I would get the convertible top error on the display. I checked all the microswitches in the boot area and they were all good.
I was able to pull codes using ISTA, cleared them and the one that came back was A98A, "incremental sensor, folding roof, direction". The "incremental sensor" is a small PCB inside the motor assembly that senses the direction of rotation of the motor using two hall effect sensors and a magnetic disc. I removed and disassembled the motor and found that the worm gear had walked down the shaft and gouged out the sensor board. I'm not entirely sure how this happened, but if you were to continue to drive the motor while the roof was all the way open or all the way closed and the worm gear was not secure on the shaft, it could walk.
In any case, if your sunroof does not move at all, this may be your culprit. I'm grabbing a used motor assembly, but I may see if I can get design a replacement increment sensor board and get it printed. It should not be too expensive.
Also, maybe I'm just dumb, but in order to manually open and close the sunroof portion of the top, there is a 5mm (?) hex head sticking out of the drive motor when you pop off the access panel on the center-bow trim. It will not turn unless you push it in and turn at the same time. It's probably in the user manual somewhere, but I couldn't actually find that described on the internets anywhere.
Last edited by jiggersplat; Mar 3, 2023 at 12:57 PM.
Allen key is usually in trunk tool kit under the flooring. Linked below.
Nice find, what that tells me is the force to open and close the sunroof position is strong and if the rails are not greases/lubed they can get stuck. I grease and lube my R52 all the time. At flex points with the top opened and when its at a 45 degree angle opened up. With the top up and closed and sunroof open, takes the side plastic trims off and grease and lube everything, then work the motor back and forth. When the top cables jam they take out the cables or the motor for the sunroof function.
