BTW, I opened up the tailgate module to look at the PCB, and man, it's crazy complex.


I figured there would just be a few transistors and relays, but there's quite a lot more in there.

Okay, I finally figured it out.


First, I took a 12V UPS battery from a battery backup (for computers) and applied it to MOT+ and MOT- on both sides. Turns out they both work fine, so the impedance of 2 ohms or 29 ohms apparently doesn't matter.


This led me to look closely at the tailgate module again, and then I noticed that one of the four wide pins in the input connector on the module had rusted through and broken clean off. It is for the RT/GE wire (the main 40A power line to the motors). That's why the output MOT+ pins on the module only put out around 2VDC even when I pushed the button to activate the motor.


I had not even noticed this pin had broken off because the pin was simply missing when I was filing/sanding/solder-tinning the other pins.


So, I have three options:


a) Try to find just the connector, which is an AMP 1-1452354-1 automotive connector.
Based on prices of other AMP connectors, it should cost about $2 per part. But it looks like I can't buy it anywhere.


b) Replace the whole module.


c) Bypass the broken pin with thick gauge wire, spliced into the wiring harness and into the module.

Getting the broken-off pin out of the female connector on the wiring harness was a pain, but there's a trick.


They designed the connector with a flip-up hatch on the side that provides access to the interior. I popped this hatch up, then used a curved dental pick to push the broken-off pin out from the inside of the connector.


Then I used jeweler's needle-nosed pliers to pull the broken-off pin free out the front. So the connector is clear, though corroded. I can scrape the corrosion off from the inside by inserting a wire repeatedly and maybe using a deoxidizing spray.

The AMP connector is a "RESTRICTED PRODUCT," so no chance of buying it.


Guess I'm going to splice around it using a thick-gauge wire and pair of male-female connectors.

from the schematic you linked the 'yellow' side (as I recall, Gelbe in german?) is the left side


So thats one question... your left side is at 2Ohms (will draw 6A) the right side is at 30, so that will draw 12/30= 0.4A.



Can you pop out the spindles? Just disconnect the ends, see if either moves? Id be cautious about applying 12VC to the spindles (pin 1+2), since I am not sure if it is a simple DC motor or a closed loop drive system of sorts.


Read this: https://www.newtis.info/tisv2/a/en/e...ration/XTgUlge


in particular you need to do a system reset to re-enable the spindle drives. Buya BMW code reader, like the foxwell 520- I think that will access those modules. Anyone now for sure?

Thanks, ard, for your help throughout this diagnostics.



Too late--I already applied 12VDC to both spindle motors, and both moved vigorously to close the hatch. I still have no idea if that amount of voltage is bad or did any damage to either spindle, but I figure it's probably okay, as it did not strike anything (the upper tailgate moved downwards from fully-open and only moved for a few inches until I quickly removed the power).


I'm pretty confident that once I splice in a bypass to the broken pin at the end of the RT/GE wire (40A power input), the whole tailgate will work again. My plan is to take apart the tailgate control module, solder in a thick wire with a male disconnect terminal and use a T-tap on the RT/GE wire.


After that, I will deal with a bad spindle if there is one.

water into the rear electronics bay damaging the tailgate control module seems to be common. Have you ruled that out? (water corrosion seems a massive hint. Shining up the pins might not have fixed it....)

and: https://www.youtube.com/watch?v=OyGMsnfNFq0

I opened up the tailgate control module (it's very easy to do, the bottom flips open) and looked at the PCB.



There does not appear to be any water damage to the module aside from the corroded connector. Of course, there could be damage that I don't see, but I think the corroded input connector blocked the water from getting further into the tailgate module.

Thanks. I will need the calibration steps after I successfully splice the 40A wire into the control module.