I know. $40 labor + parts that were cheaper from Tesla than eBay (wish I knew at the time). But it was 2.5 weeks for the appointment and since the car won't lock I couldn't drive it anywhere. I might just keep the appointment and see if they will install the back cover for $40 !
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Rear trunk won't open
- Thread starter commasign
- Start date
You may be able to lock the doors by touching the lock icon on the center display before exiting. I hear that trick has worked for others in the pat
I’m a longtime lurker who recently joined the stuck trunk club on a road trip with friends. 
Many thanks 
to those who discovered and documented the black plug procedure. With that, I was quickly able to open the liftgate once we returned home.
I’ve spent some time experimenting and playing around with the relevant mechanisms in an effort to gain insight into how the auto-close and open processes are supposed to work. As such, this posting gets a bit lengthy in an attempt to include relevant details. I hope to advance the cause and increase my, and the community's, understanding of this fault. Based on the experiences documented in this thread, it seems likely that this problem would disappear if I replaced the high-torque cinch motor and/or the latch. My curiosity has taken hold, however, and I would like to dig deeper to gain a fuller understanding of what is going wrong.
November 2016 build date Model S
TL;DR — The latch, cinch motor, and supporting infrastructure appear to be functioning properly when inspected individually. How does one bench test the sensors/switches and actuator/solenoid in the latch? My efforts to find a wiring diagram, pinout specs, or troubleshooting procedure have come up empty.
At this point in my experimentation, I’m wondering how to bench test the latch mechanism. My efforts to find troubleshooting procedures, a wiring diagram, or a pinout schematic for the four-pin connector have failed miserably. I’ve used Tesla and Mercedes part numbers in my searches. Still, no dice. I’m hoping that is a testament to my poor searching skills and someone here can point me in the right direction.
When the liftgate is fully and quickly closed by hand (no cinch motor help required), the latch will release as expected. The trouble starts when the cinch motor is activated to fully close the liftgate from a half-closed state. When the latch then opens, the cinch motor does not release. Because the cinch is still drawn tight, the latch only releases part way. The liftgate is then in a partially open state where it can neither be fully opened nor fully closed. The emergency release cable has no hope against the grip the cinch motor has on the latch mechanism.
When the liftgate is in this stuck-in-the-middle state, the black plug method will release the cinch motor. That seems to indicate the cinch motor and associated wiring are intact and functioning as designed.
So, that presents me with a quandary. Why doesn’t the lift gate controller release the cinch motor? Is a sensor, presumably in the latch, failing to indicate the partially opened state? The system seems to know when the latch is partially closed. Otherwise, it wouldn’t have actuated the cinch motor in the first place. Is there maybe something awry within the liftgate controller itself? Maybe the sensor has only partially failed and can indicate when the latch has been half closed from an open state, but cannot indicate when the latch has been half opened from a closed state? A wiring diagram or schematic for the 4-pin connector would be most helpful. Is there a suggested test procedure to further diagnose problems with the latch?
I’ve disassembled, inspected, lubricated, reassembled, and tested the high torque cinching actuator. I found no evidence of malfunction or wear. It readily operates in both directions even with as little as 3 volts from my bench power supply.
I’ve also removed the latch and operated it on the bench. It seems to be working well mechanically with no binding. The emergency release cable opens it up with minimal effort and the cable that runs to the cinch motor operates with no binding or excess friction.
Many thanks to those who discovered and documented the black plug procedure. With that, I was quickly able to open the liftgate once we returned home.I’ve spent some time experimenting and playing around with the relevant mechanisms in an effort to gain insight into how the auto-close and open processes are supposed to work. As such, this posting gets a bit lengthy in an attempt to include relevant details. I hope to advance the cause and increase my, and the community's, understanding of this fault. Based on the experiences documented in this thread, it seems likely that this problem would disappear if I replaced the high-torque cinch motor and/or the latch. My curiosity has taken hold, however, and I would like to dig deeper to gain a fuller understanding of what is going wrong.
November 2016 build date Model S
TL;DR — The latch, cinch motor, and supporting infrastructure appear to be functioning properly when inspected individually. How does one bench test the sensors/switches and actuator/solenoid in the latch? My efforts to find a wiring diagram, pinout specs, or troubleshooting procedure have come up empty.
At this point in my experimentation, I’m wondering how to bench test the latch mechanism. My efforts to find troubleshooting procedures, a wiring diagram, or a pinout schematic for the four-pin connector have failed miserably. I’ve used Tesla and Mercedes part numbers in my searches. Still, no dice. I’m hoping that is a testament to my poor searching skills and someone here can point me in the right direction.
When the liftgate is fully and quickly closed by hand (no cinch motor help required), the latch will release as expected. The trouble starts when the cinch motor is activated to fully close the liftgate from a half-closed state. When the latch then opens, the cinch motor does not release. Because the cinch is still drawn tight, the latch only releases part way. The liftgate is then in a partially open state where it can neither be fully opened nor fully closed. The emergency release cable has no hope against the grip the cinch motor has on the latch mechanism.
When the liftgate is in this stuck-in-the-middle state, the black plug method will release the cinch motor. That seems to indicate the cinch motor and associated wiring are intact and functioning as designed.
So, that presents me with a quandary. Why doesn’t the lift gate controller release the cinch motor? Is a sensor, presumably in the latch, failing to indicate the partially opened state? The system seems to know when the latch is partially closed. Otherwise, it wouldn’t have actuated the cinch motor in the first place. Is there maybe something awry within the liftgate controller itself? Maybe the sensor has only partially failed and can indicate when the latch has been half closed from an open state, but cannot indicate when the latch has been half opened from a closed state? A wiring diagram or schematic for the 4-pin connector would be most helpful. Is there a suggested test procedure to further diagnose problems with the latch?
I’ve disassembled, inspected, lubricated, reassembled, and tested the high torque cinching actuator. I found no evidence of malfunction or wear. It readily operates in both directions even with as little as 3 volts from my bench power supply.
I’ve also removed the latch and operated it on the bench. It seems to be working well mechanically with no binding. The emergency release cable opens it up with minimal effort and the cable that runs to the cinch motor operates with no binding or excess friction.
Thank you! I just ordered one for my 2016 MS that this part more than likely failed last night.
Same thing here. I now have two removed ("faulty") cinch motors. Both spin freely in both directions with very little applied voltage. When I acquire a third that also "works" I intend to take the small (Mabuchi?) motor apart and check on the condition of commutator and brushes.
I don't know if this is the right motor so don't go buying unless you are either certain or don't care about the small cost. https://www.aliexpress.com/item/1005005414164586.html
My son ran into this problem today (so that's three times now on the same car, a Model S 2015 85D). Waiting for a mobile service appointment on Thursday.
Bruce.
Bruce.
NewbyMaybe
Newby1Kenowby
Thanks, I might try playing with the stoppers. Removing the cinch / cinch motor, while probably easy for someone accustomed to working on cars, is out of my comfort zone.
(I appreciate how much people have discovered about this issue since it first started happening in 2016.)
Bruce.
whitex
Well-Known Member
Watch the mobile tech perform the service, then look for a good deal on a spare motor over the next couple of years. This way next time it happens, you will be prepared. Working on your own car is not rocket science. The hardest part I think is starting. In this case, if the cinch motor is already broken, you're not likely going to mess it up any worse. If you fail, you just make a mobile tech appointment (one thing I miss from my Tesla days is mobile techs - always had great experiences with them, my parents recently wanted to swap winter to all-season tires on their model Y, turns out even that can be done by a mobile tech - I would have swapped out the wheels for them, as I swap my car 4 times a year and my wife's car twice a year, but they live far from me, not worth the drive).
PS> Purely coincidentally, I was just working on the rear hatch of my latest car (not a Tesla) this weekend - adding some secret sauce of my own to the car, as I did with my Teslas, The only difference between working on a Tesla than other car is that you can lookup howto videos for Teslas, I had to figure out all on my own how to take apart this hatch, so it took way longer (next time it will be quick, will post on the other car forum for others to save them time as I did for Tesla in my Tesla days)..
NewbyMaybe
Newby1Kenowby
Putting the back plastic part back on was one of the biggest pains ever (for me anyway).
Cheburashka
Active Member
whitex
Well-Known Member
The very first I did when I got my first Tesla was to get a bag of spare clips, IIRC there was 2 kinds. Back in 2013 Tesla charged me $1 per clip, since I learned you can buy the identical clips for Toyota IIRC (perhaps other brands) for pennies per clip. If you work on your car, there is always a chance a clip can be damaged.
Conclusion: Mobile service came by on Thursday and replaced the cinching actuator. Interestingly it's a new part/part number, "HIGH FORCE CINCHING ACTUATOR(1003549-00-D)". (The part used on the previous repair was "CINCHING ACTUATOR(1003549-00-A)".) Here's hoping it's different enough, in a positive way, that we don't need to do this again.
Parts: $70.00
Labor: $47.70
Tax: $6.13
Total: $123.83
The local Tesla store offered to do a test-drive-from-home during the mobile service appointment. So I asked for (and got) a test drive in a Highland Model 3. Nice ride. I guess they figured that anyone getting a 9-year-old Tesla fixed might be wanting to replace it (I'm not).
Bruce.
Parts: $70.00
Labor: $47.70
Tax: $6.13
Total: $123.83
The local Tesla store offered to do a test-drive-from-home during the mobile service appointment. So I asked for (and got) a test drive in a Highland Model 3. Nice ride. I guess they figured that anyone getting a 9-year-old Tesla fixed might be wanting to replace it (I'm not).
Bruce.
Last edited:
Cheburashka
Active Member
BioSci
Member
I just had Tesla mobile service do this repair on my 2020 MS. I could manually close and release the trunk, but the car wouldn’t lock or use TACC/FSD. He replaced a 'high force cinching actuator' and an 'assembly liftgate latch power release' under warranty. I had to pre-approve about $220 parts/labor charges before he arrived in case it was broken because of owner damage, but wasn’t charged. Works fine now.
Yea. I purchased the replacement motor elsewhere (eBay) and it turned out to be more ($88 or something).
Conclusion: Mobile service came by on Thursday and replaced the cinching actuator. Interestingly it's a new part/part number, "HIGH FORCE CINCHING ACTUATOR(1003549-00-D)". (The part used on the previous repair was "CINCHING ACTUATOR(1003549-00-A)".) Here's hoping it's different enough, in a positive way, that we don't need to do this again.
Parts: $70.00
Labor: $47.70
Tax: $6.13
Total: $123.83
The local Tesla store offered to do a test-drive-from-home during the mobile service appointment. So I asked for (and got) a test drive in a Highland Model 3. Nice ride. I guess they figured that anyone getting a 9-year-old Tesla fixed might be wanting to replace it (I'm not).
Bruce.
I had the same issue that's mentioned in this thread on my 2015 Model S 85D. After closing my trunk last week, I noticed it was indicating open still and when I tried to open it again, it would just beep twice (like when you're closing it) but it would not open. I noticed I could move the trunk slightly up and down so it wasn't completely latched. If I let the car sit for a bit, I was able to open the trunk by just pulling up on it (seems like the secondary latch or whatever was holding it down was no longer engaged), but after closing the trunk again, the problem showed up again.
I scheduled service through the app and initially received an estimate for close to $400. The day prior to the mobile technician showing up, I got a messaging saying after review, they were going to reschedule me to bring the car in. I explained to them what I mentioned above (the fact I was able to open the trunk) and also that I found other owners with the same issue that had the "high force cinching actuator" replaced which fixed it (based on the post by @bmah above, so thanks for that), and they messaged back saying since I could open the trunk, they would keep it scheduled as mobile service.
When the mobile service technician showed up, I explained everything above and he said he also thought it was the high force cinching actuator and would start with replacing that first. After replacing it, everything was working normal again and the final cost was significantly cheaper:
Parts: $70.00
Labor: $36.90 (0.18 hours)
Tax: $5.86
Total: $112.76
I didn't get to do a test-drive-from home though, which would have been great since I'm considering selling this car for the new Model 3.
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