ISM replacement
Out Of Control!!
Joined: Apr 2019
Posts: 11,958
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From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
ISM cramped quarters 🫤
From what I've seen... you could cut off a Torks bit short to fit between ISM and chassis - That's far better than dropping tranny out....
-2- CHEAT TIP:
You can undo tranny from its mount and torque it sideways to gain extra clearance.
Lets us know what you got... I am in the mood of pulling my ISM out as well to rework the bugs out of it....
Thread Starter
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Joined: Dec 2022
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w212
Thank you for the excellent tips. I will try both this coming weekend and report back. First it was the conductor plate and now I started getting redundancy system activated short to positive code P179A12 , tranny would not shift out of park. 2 days of not touching vehicle and its perfect but I know it's only a matter of time till it happens again so rather dig into ISM.
Thank You
Thank You
Out Of Control!!
Joined: Apr 2019
Posts: 11,958
Likes: 6,802
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
ISM
Thank you for the excellent tips.
I will try both this coming weekend and report back.
First it was the conductor plate and now I started getting redundancy system activated short to positive code P179A12 , tranny would not shift out of park. 2 days of not touching vehicle and its perfect but I know it's only a matter of time till it happens again so rather dig into ISM.
Thank You
I will try both this coming weekend and report back.
First it was the conductor plate and now I started getting redundancy system activated short to positive code P179A12 , tranny would not shift out of park. 2 days of not touching vehicle and its perfect but I know it's only a matter of time till it happens again so rather dig into ISM.
Thank You
You are definitely right about dealing with it on your own schedule before it pops a social-finger to get towed. Same reasons for me!
I am planning to open this tin-can to:
- lubricate dry mechanicals
- solder the collection of loose pins
- weatherize the circuit board
- RTV silicone the leaky connector
This is an essential module acquainted with top VIP's... It has to be in great shape, better than new.
In the mean time it may respond well to "car reboots".
🤞
Last edited by CaliBenzDriver; Nov 21, 2023 at 09:09 PM.
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Joined: May 2021
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From: US
2008 E350, 2012 ML350, 2014 E350, 2015 ML350
Thank you for the excellent tips. I will try both this coming weekend and report back. First it was the conductor plate and now I started getting redundancy system activated short to positive code P179A12 , tranny would not shift out of park. 2 days of not touching vehicle and its perfect but I know it's only a matter of time till it happens again so rather dig into ISM.
Thank You
Thank You
or
Last edited by JCM_MB; Nov 21, 2023 at 09:28 PM.
Thread Starter
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Joined: Dec 2022
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w212
Ok, so the ism can be removed with the right tools and also dropping the transmission bracket. I'm stuck at the part where I'm not sure if the new ism is placed in Neutral or Drive etc during install. 1 video says to place into neutral and another says place into drive before bolting ism in?
Out Of Control!!
Joined: Apr 2019
Posts: 11,958
Likes: 6,802
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
manually shifting selection
Ok, so the ism can be removed with the right tools and also dropping the transmission bracket.
I'm stuck at the part where I'm not sure if the new ism is placed in Neutral or Drive etc during install. 1 video says to place into neutral and another says place into drive before bolting ism in?
I'm stuck at the part where I'm not sure if the new ism is placed in Neutral or Drive etc during install. 1 video says to place into neutral and another says place into drive before bolting ism in?
The video shows how you can shift the gearbox with a pair of pliers, right?
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Out Of Control!!
Joined: Apr 2019
Posts: 11,958
Likes: 6,802
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
you need to manually dial the tranny to match the ISM position you've just read.
I am curious how did you manage to access the side screws to remove ISM unit from the car? I want to get my ISM out too... how much time to drop it?
++++ Don't try to manually spin the ISM gear output. Dial tranny to match the ISM position.
++++ Spread RTV silicone to provide good weather seal to connector (away from contacts).
✌️
Last edited by CaliBenzDriver; Nov 24, 2023 at 10:23 PM.
Thread Starter
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w212
Ok, so I'll just move tranny to N and slap it in since ism is brand new unit. I removed it by dropping rear transmission mount which is very easy and then using T30 bit on a slim torx dedicated wrench from Amazon. The ism bolts are super loose and took almost no torque to remove. Once I had the car on ramps it took all of 50min to remove taking my time.
Out Of Control!!
Joined: Apr 2019
Posts: 11,958
Likes: 6,802
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
opportunity
Ok, so I'll just move tranny to N and slap it in since ism is brand new unit.
I removed it by dropping rear transmission mount which is very easy and then using T30 bit on a slim torx dedicated wrench from Amazon.
The ism bolts are super loose and took almost no torque to remove.
Once I had the car on ramps it took all of 50min to remove taking my time.
I removed it by dropping rear transmission mount which is very easy and then using T30 bit on a slim torx dedicated wrench from Amazon.
The ism bolts are super loose and took almost no torque to remove.
Once I had the car on ramps it took all of 50min to remove taking my time.
It's amazing you noticed how bolts are loose on these cars. Some bolts are made of aluminum, "one time use only" at least on timing covers.
Can you link the good AMZ wrench ?
Do you want to spend 100 save 20x ?
Out Of Control!!
Joined: Apr 2019
Posts: 11,958
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From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
Thank You for all the help! I used the cheap set https://www.amazon.com/gp/aw/d/B07RN...b_b_asin_title
just had to extend the handle.
just had to extend the handle.
Big saving... if what i was reading is correct (pls correct me) the nice scanner
LAUNCH C-READER ELITE 431 near $100/120 should be able to copy cat old ISM into new one.
Double check that ability to x-code.
I am planning to try and hack the Android on that scanner for fun - My ISM will get boosted not replaced.
MBWorld Fanatic!
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From: US
2008 E350, 2012 ML350, 2014 E350, 2015 ML350
Thank You for all the help! I used the cheap set https://www.amazon.com/gp/aw/d/B07RN...b_b_asin_title
just had to extend the handle.
just had to extend the handle.
MBWorld Fanatic!
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From: Jakarta-Indonesia
2014 - W212.065 - E400 ( M276.820, 3 liter Turbo) RWD not Hybrid
Thank You for all the help! I used the cheap set https://www.amazon.com/gp/aw/d/B07RN...b_b_asin_title
just had to extend the handle.
just had to extend the handle.
I BOUGHT IT 5 minutes ago.....
Thread Starter
Junior Member
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w212
Replacement complete, only difference was the new unit came set in P position so I did not have to manually move transmission into Neutral. Transport protection and calibration both worked with the scanner I referenced in prior post. See how long this lasts.
Thank you all who posted and helped. Happy Holidays
Thank you all who posted and helped. Happy Holidays
Junior Member
Joined: Dec 2012
Posts: 19
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From: Toronto
W212R E63S AMG
Replacement complete, only difference was the new unit came set in P position so I did not have to manually move transmission into Neutral. Transport protection and calibration both worked with the scanner I referenced in prior post. See how long this lasts.
Thank you all who posted and helped. Happy Holidays
Thank you all who posted and helped. Happy Holidays
hello, any update on this? I have the same problem… it’s been ongoing for the last 3 months. It’s been such a pain… I have had an independent shop replace the ISM with new and reprogram… same issue after a week. Also replaced steering column shifter. Still same problem. Changed both main and auxiliary batteries. Still the same problem. I need some hope and a miracle…
Last edited by akoustic; Jul 23, 2024 at 08:17 PM.
MBWorld Fanatic!
Joined: May 2021
Posts: 2,524
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From: US
2008 E350, 2012 ML350, 2014 E350, 2015 ML350
hello, any update on this? I have the same problem… it’s been ongoing for the last 3 months. It’s been such a pain… I have had a independent shop replace the ISM with new and reprogram… same issue after a week. Also replaced steering column shifter. Still same problem. Changed both main and auxiliary batteries. Still the same problem. I need some hope and miracle…
Thread Starter
Junior Member
Joined: Dec 2022
Posts: 20
Likes: 4
w212
hello, any update on this? I have the same problem… it’s been ongoing for the last 3 months. It’s been such a pain… I have had an independent shop replace the ISM with new and reprogram… same issue after a week. Also replaced steering column shifter. Still same problem. Changed both main and auxiliary batteries. Still the same problem. I need some hope and a miracle…
Out Of Control!!
Joined: Apr 2019
Posts: 11,958
Likes: 6,802
From: Silicon Valley
W212 MY'14 M276-3.5NA @75kMi
DOMINO EFFECTS...
hello, any update on this? I have the same problem… it’s been ongoing for the last 3 months. It’s been such a pain…
I have had an independent shop replace the ISM with new and reprogram… same issue after a week. Also replaced steering column shifter.
Still same problem.
Changed both main and auxiliary batteries. Still the same problem.
I need some hope and a miracle…
I have had an independent shop replace the ISM with new and reprogram… same issue after a week. Also replaced steering column shifter.
Still same problem.
Changed both main and auxiliary batteries. Still the same problem.
I need some hope and a miracle…
In order to locate the exact miracle you ordered, we need a good chassis scan to help you diagnose this issue!
Your ISM issue is shared by many to various degree without any fault code.
Your ISM acting up pretty much guarantees ECU/TCU are also acting poorly...
You can try whole chassis reboot (CGW/ESP) to see if chassis responds well to that free temporary relief.
Let us know.
Last edited by CaliBenzDriver; Jul 24, 2024 at 12:01 PM.
Newbie
Joined: Oct 2025
Posts: 3
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From: USA
ISM issues are fairly common in the W212 models, especially as the car gets older. The Intelligent Servo Module controls gear shifting electronically, so when it starts failing, you’ll often notice symptoms like the transmission not engaging, stuck in park, or random warning messages.
Before replacing it outright, it’s worth checking the wiring harness and connector pins for corrosion or loose contact — sometimes a simple cleaning can fix intermittent faults. If replacement becomes necessary, make sure to get the ISM coded properly to your vehicle’s VIN using STAR Diagnostics, otherwise it won’t communicate correctly with the transmission control unit.
Also, avoid buying used ISMs unless you’re sure they’ve been properly reset (“virginized”), because once coded to a car, they usually can’t be reused without specialized tools. A new or remanufactured unit from a reputable supplier is often the safer choice in the long run.
Before replacing it outright, it’s worth checking the wiring harness and connector pins for corrosion or loose contact — sometimes a simple cleaning can fix intermittent faults. If replacement becomes necessary, make sure to get the ISM coded properly to your vehicle’s VIN using STAR Diagnostics, otherwise it won’t communicate correctly with the transmission control unit.
Also, avoid buying used ISMs unless you’re sure they’ve been properly reset (“virginized”), because once coded to a car, they usually can’t be reused without specialized tools. A new or remanufactured unit from a reputable supplier is often the safer choice in the long run.
