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2020-2024 Outback (2022-2025 Wilderness) Transmission Control Module (TCM) / Software Enhancement (TSB 16-150-24R)

10K views 20 replies 12 participants last post by  CASkiBum  
#1 · (Edited)
Have a 2020-2024 outback? 2022-2025 wilderness? Transmission jerking or a judder sensation felt from the powertrain during braking with the air conditioning on? Shudder is felt from the powertrain along with a screeching type of sound?

then this TSB might be for you!

What this thread is about:
  • The fact there is a TSB for this concern, and questions about those specific conditions
  • Experiences getting this specific fix applied at a subaru service center
  • Changes to the TSB over time - the official resolution, introduction of newer part numbers. If it's in the TSB, and is changed, it's fair game.

Discussions found elsewhere that don’t belong in this thread:

NOTE: there is a recall for some 2.4L turbo transmission issues, but it’s a separate problem. See the recall thread here


Observations:
  • The revised service bulletin EXTENDS the applicability back to the start of the model generation. Previously, it was 2023-2024 outbacks. Now it is 2020-2024 model years.
  • Outback models will have a software reprogramming applied. If that fails, for whatever reason, a NEW TCM is put in the car.
  • 2024 Wilderness model guidance has changed - previously, it was TCM replacement ONLY. Now, it's TCM replacement, followed by a check to see if the software is new enough to contain the countermeasures. The change is because the original TCMs could not be programmed due to a software incompatabilty, they required direct replacement. The change for verifying the installed software AFTER a hardware TCM replacement is because not all TCMs may have software revisions that include the required countermeasures. No part numbers given for known "good" TCM - verification must be performed after each TCM replacement.
  • There is a chart for what VIN range is potentially affected, and for the Outback it is listed as TBD (to be determined).
  • The graphic for the "judder sensation occurs" is epic.
  • There is a NEW service bulletin that references this one, and several other similar issues, so it functions as a sort of lookup document, and has some interesting things in it. This is TSB 16-151-24R. It includes things from this service bulletin, and some other troubleshooting/diagnostic information. Worth a look. I attached it too.

Summary of TSB 16-150-24R:

Bulletin Number: 16-150-24R
Date:
12/03/24
NUMBER: 16-150-24R

APPLICABILITY:
2020-24MY Legacy 2.4L
2020-24MY Outback 2.4L
2019-24MY Ascent
2022-24MY WRX
2022-25MY Outback Wilderness


SUBJECT: Transmission Control Module (TCM) / Software Enhancement

INTRODUCTION:
This bulletin announces availability of new reprogramming files developed to address the two symptoms described below:

SYMPTOM 1: A jerk or judder sensation felt from the powertrain during braking with the air conditioning on.
SYPMTOM 2: A shudder is felt from the powertrain along with a screeching type of sound.

NOTE: Both of these symptoms are not related with a fault code.

The new files contain enhanced software optimizing input clutch application along with enhanced hydraulic pressure control during braking/deceleration. On some model applications, the Transmission Control Module (TCM) will require replacement along with a final reprogramming (if applicable). If a customer reports either of the symptoms described above and their vehicle is within the VIN range listed below, follow the procedures outlined within this bulletin.

Model - Starting VIN
Outback - TBD
Legacy - N/A
Ascent - R3439833
WRX - R8807951

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Revision History:

Oct 11, 2024 - thread created. Original TSB attached
Nov 17, 2024 - updated TSB attached. summary section updated with new date, and more model years affected
Dec 05, 2024 - attached TSB 16-151-24 for reference
Apr 07, 2025 - updated TSBs attached
 

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#2 ·
That's really interesting...I've noticed maybe 2-3 instances where I thought there were odd shifts/jerks in the drivetrain with the a/c on. There's a certain spot in my morning commute where I notice it, so I'll have to pay more attention and see if it aligns with what the TSB is saying. (2023 Onyx XT)
 
#3 ·
It’s always happened without the AC being on. I never have my AC on. Why do they think it’s only a small group of VIN numbers? This has been an issue since the 2018 Ascent FA24 turbo and every vehicle with this motor has this issue.

Please update us on the results.
I’ve seen a few post about this a month or two now but no one has ever talked about any results which is very odd.
 
#4 · (Edited)
16-150-24R dated 10/31/24 is now current and includes some model year 2025 Outback Wilderness.

It appears some model year 2025 Outback Wilderness vehicles may require TCM reprogramming to add software countermeasures for symptom 2. 25MY OBW may have part number 30919AK11D or 30919AK11C TCM installed with software countermeasures for symptom 1. It appears chain slip caused by input clutch slip in symptom 2 is associated with the cicada like screeching noise, and I’m certain this has not occurred on my 25MY OBW.
 

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#6 ·
Well, there ya go.

The newer service bulletin has extended the range of affected vehicles too - it was only 23-24 outbacks, and 23-25 wilderness - now it’s outbacks starting with the 2020 model year. Same for other vehicles affected.

From the reading the service bulletin - the guidance has changed some - additions are shown in yellow highlight, but things removed are not shown … one of the things removed was text about replacement of the TCM - it used to say the wilderness was replacement only, and that was it. Done. Also noted in big red letters.

now, it’s replacing the older TCM, and then a verification of the software version - because not all replacements might have the latest firmware.

A reason for the hardware replacement is now explained - it is because there is an error when trying to reprogram older units - software incompatibility. The newer units can be reprogrammed, and should come with the newer software, but if not, then it’s applied. So a verification step was also added. This not only checks the software version, but also verifies that the replacement doesn’t show that error.
 
#7 ·
A reason for the hardware replacement is now explained - it is because there is an error when trying to reprogram older units - software incompatibility. The newer units can be reprogrammed, and should come with the newer software, but if not, then it’s applied. So a verification step was also added. This not only checks the software version, but also verifies that the replacement doesn’t show that error.
That's critically important knowledge for the owners as sadly, some dealerships didn't read that deep into the TSB, and owners have been without their cars for a while when the TCM bricks during the update and they don't have a replacement.

(of course, it's the dealers who should be staying on top of that, but, since a few are not, I hope owners, being armed with that information, make sure their dealer is ready for the possibility)
 
#8 · (Edited)
I recently(12/3/24) brought my 23 OB Wilderness in for 30K major service and asked them to do the TSB 16-151-24 update. They said "TCU update not available at this time" How long after SOA releases an update should I expect to have to wait for my dealer to have access to it? I'm experiencing the surge/slam with the A/C on and off, and up at highway speeds (65-80mph) when accelerating and the transmission "upshifts". It's getting worse.
 
#10 ·
I recently(12/3/24) brought my 23 OB Wilderness in for 30K major service and asked them to do the TSB 16-151-24 update. They said "TCU update not available at this time" How long after SOA releases an update should I expect to have to wait for my dealer to have access to it? I'm experiencing the surge/slam with the A/C on and off and up at highway speeds when acccell accelerating and the transmission "upshifts". It's getting worse.
23 OB onyx XT same. Horrible when cold first several stops or slowing down with or without HVAC on. Shudder/Judder/jolt during ACC usage when the system has to decel/accel or accelerate around the 75-85mph. Took it in and they did a relearn and a CVT transfer clutch assembly overhaul. Which did nothing except improve straight line acceleration without the car shimmying and shuddering. It’s gotten bad. Found the updated TSB’s and scheduling service to have them try either the new software updates. Based on the extensive TSB update my answers come to CVT replacement. It’s gotten to where passengers are like damn like I’m trying to make the car shudder and kick. The slowing down to a stop and it lurching and kicking forward is annoying.

here is the info from last visit:

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#11 · (Edited)
My model year 2025 OBW September 2024 build has the new TCM part number and latest software load, so you should be okay. Subaru will update the TSB after documenting the VIN cutoff for model year 2025. I would confirm the TCM part number during your pre-purchase inspection.
 
#14 ·
Hey gang- so update, I am 40,700 miles and going to have to get my outback in right away!!! It all of sudden is not wanting to accelerate forward or backwards at times slamming and noisy from the rear. If you are in driveway, parking lot, small tight or neighborhood/drive thru driving scenarios it is catching and slamming hard from the rear! It reminds me of having a tow strap attached to the back of the car and trying to accelerate and tow another vehicle behind you and slams from the slack in strap and a heavy vehicle being pulled from a standstill. Especially on turns feels like the back wheels and back end is going to fall out. It started a couple days ago, pulled out left onto highway from our side road, it made the loud whining noise, then as I was accelerating down the road it would not stop with the judder or shudder. I had to come to a stop and then it cleared up slightly. Roughly and noisy driveline noise, then when I got to my destination turning into parking lot I barely got it parked. Backing up is really bad and turns. No smoke, no leaks, and no lights. Car runs crappy, power has been limited from a rocket it used to be to just like driving the 2.5. Sorry for the long post. I will update once I get it in, work is just so busy…. Will have to get loaner car. Besides remaining Subaru powertrain warranty I have the 6yr/100k gold I believe warranty it was the best one they offer. I am glad. Cause my baby needs a transmission replacement I am sure.
 
#16 ·
I experienced the shudder at deceleration (under 20 mph) with AC on while coming to a stop, which is a symptom highlighed in this TSB. Dealer was unable to reprogram my TCM, as it was an older model placed in my '24 OBW. I received a new TCM with the newest programming last week. The quality of the shifting in all conditions is noticeably improved. The shudder while decelerating is gone. And all shifts both up and down are crisper. I really notice the faster shifting at more consistent RMPs when I am accelerating to a freeway merge.

This TSB is definitely worth attending to.
 
#17 ·
I experienced the shudder at deceleration (under 20 mph) with AC on while coming to a stop, which is a symptom highlighed in this TSB. Dealer was unable to reprogram my TCM, as it was an older model placed in my '24 OBW. I received a new TCM with the newest programming last week. The quality of the shifting in all conditions is noticeably improved. The shudder while decelerating is gone. And all shifts both up and down are crisper. I really notice the faster shifting at more consistent RMPs when I am accelerating to a freeway merge.

This TSB is definitely worth attending to.
I also thought mine shifted and ran a lot better after the upgrade on my 2024 OBW.. Seemed to be friskier when starting off too, more like the MIL's Ascent. Have not tried any panic stops on the highway with AC on, but that was the worst thing I experienced. It shuddered and bucked like I had very warped rotors, but they are fine. Hopefully it addressed that issue too :)
 
#18 ·
So, some slight updates, they still have my 23 OB XT in service, found oil pump leak, found that it needed throttle body, upper intake or air thing cleaning I forget right now cause I took call from dealer at work, they have to clean all that which is covered under power train warranty, which was causing bad idle and stumbling, they said probably looking at another week or so as they are awaiting SOA on transmission data and transmission issues…? Again, texting service advisor and a quick call days ago. I have a 25 forrester loaner… wow I miss my beast! You have to plan and wait to exit onto highways, side roads, etc. plus my OB has a lot of features this doesn’t. Like blind spot, RAB, auto dimming, leather, remote trunk, etc. but it’s nice and I’m thankful to have it. Will post everything in detail once I have it from Subaru. They have had it since 3/4/25. Loaner car had 37miles on it when I got it..now has 700 lol. Hope they put new trans in my OB. Software isn’t the issue it’s bad chain slip or something of that nature. Thanks for all the info and posting.
 
#19 ·
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Update 3/20/25: I got my OB back! Replaced CVT transmission assembly, replaced engine oil level sensor O-Ring; performed TSB 9-74-21R intake/egr cleaning, oil change, four wheel alignment and software update. I’m going to attach pictures of the work sheets so it makes sense and you have the numbers and info so if you are having these issues. Sorry couldn’t get pictures in order of reading
 

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