Next diagnostic steps for E70 Power Tailgate not working?
 

Hi, everyone--


I've got a 2008 X5 E70 3.0si that has a power tailgate that suddenly stopped working.


I don't think it's the battery, because the power tailgate does not operate even when the vehicle is running. The alternator appears to be working, as the running voltage is just above 14V.


The mechanized latch operates (tailgate will lock and unlock). The red button to close the latch is lit, but pressing it just causes a motor to make a noise and then the tailgate makes a little movement but stops like it's stuck.


I have pulled the two fuses on the chart: Fuse 99 (40A) and fuse 121 (5A), and both test okay.


Now, I'm lost. What's the next thing to check or do?


I will keep reading other threads but haven't found anything that goes through all the steps yet.



I have no idea how to test the powered struts, but I figure that's what I'd test next.


Thanks in advance!

do you have a voltmeter and schematics?


www.newtis.info

Definitely have a voltmeter. Didn't even know there are schematics available to the public.
Let me go look for them... Thanks!

Found it--thanks very much for the link!


Here is the link to the exact page for the wiring diagram.



https://www.newtis.info/tisv2/a/en/e...ration/lcnZ3ew

Just curious: is it true that the power tailgate system will throw codes that pinpoint the exact failure?


If so, does anyone know which code readers can pull these codes? Just checking before I waste money buying a code reader that won't do the job.


Thanks in advance!

Absolutely not.


Out of curiosity, someone selling service tell you that?

No, I remember reading it in some discussion thread while trying to troubleshoot this. Can't remember how to find the discussion, though.


I remember the poster said that one of the two lift piston-like things threw a code that identified which one to replace.

I took the power tailgate module out of the back and one of the connectors is corroded badly by water. I'll try to sand/file the connector contacts and get it shiny new again.
Might be the problem, or maybe there are multiple problems.


I may have to replace the cable harness (the one with the female plugs on it), since the pins are not exposed and thus can't be sanded.

Okay, I filed the pins a little bit and used acid flux paste and tinned the pins so that they are shiny. It is the input connector on the tailgate module (has RT/GE and RT/VI power in).


I stuck a wire into each of the pins on the female plug and scraped away.



I measured the voltage on both the white and black output plugs across MOT+ and MOT-. Both measure about 2.4VDC. I also measure 12VDC on both the white and black output plugs on the HALL_12V pin (GE on one, GE/SW on the other).


So the module looks okay. I can't prove that it's okay, but the output for both left and right sides match.


Then, I measured the spindles themselves. Measuring the resistance across MOT+ (GE/RT) and MOT- (GE/BR) came out to 2 ohms. Measuring the resistance across MOT+ (BL/RT) and MOT- (BL/BR) came out to 29.5 ohms.


So clearly, one motor is different than the other motor. Here are the two critical questions:


a) Which ohm reading indicates a broken motor, the 2 ohm or the 29.5 ohm?


b) Which color pair of wires is left, and which is right? In other words, is GE/RT & GE/BR the left side or the right side?


I figure I can answer b) by taking one of the spindles out and looking at the colors of the wires.


a) is the real critical question, because it can save me $250 to buy the correct side.


Thanks in advance!

Based on what I'm reading about 12VDC motors, the 2 ohm reading is much more likely to be correct for a good, working motor.


I suppose that if I take the spindle out and apply 12VDC to the motor, the good one will turn, but what if the motor is not meant to be driven by 12VDC?

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.

Good news--splicing a T-tap ($3 from Autozone) and a 14AWG wire) around the broken pin into the module (soldered directly to the PCB) solved the problem.



The tailgate did not need any reset, although it did not work immediately.
I tried a couple of times and could hear faint clicks, then it started working properly.


It probably could benefit from a calibration, but then again, nothing should have wiped the memory from the factory calibration.