SL/R231: Active Multicontour Seat Malfunction
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From: Nova Scotia, Canada
2019 SL450; 2023 M850i coupe
Active Multicontour Seat Malfunction
All Active Multicontour Seat functions (Lumbar, Massage and Side Bolsters) stopped working in the middle of a two hour drive. Seat position controls and seat heating worked normally.
Both batteries checked fully charged when I got home, so I don’t think it went into power saving mode to preserve battery life.
I briefly shut the car off and on, and then did a “Seat Reset” via the center console display to see if that would help, but no joy.
Once I got home and let the car set for an hour or so, everything started working again.
Has anyone experienced this? Any ideas?
Thanks!
Both batteries checked fully charged when I got home, so I don’t think it went into power saving mode to preserve battery life.
I briefly shut the car off and on, and then did a “Seat Reset” via the center console display to see if that would help, but no joy.
Once I got home and let the car set for an hour or so, everything started working again.
Has anyone experienced this? Any ideas?
Thanks!
Last edited by hornethandler; Mar 23, 2023 at 09:00 AM.
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From: Nor-Cal
2020 GLC300 -2014 Sl550 - 1997 SL600
Software glitch? Intermittent electrical issues are always hard to track...
Hopefully it won't happen again, but at least if it does, it may be easier to track.
It probably triggered a code in XENTRY. But without a way of reading the chassis code that wont help...
Besides checking fuses and resistance/load testing main battery. There's a control module in the back that may be malfunctioning. That would be my first suspect, but may also be a bad ground.
Were both seats affected?
Good Luck
Last edited by crconsulting; Mar 23, 2023 at 01:27 PM.
Thread Starter
Senior Member
Joined: Oct 2019
Posts: 293
Likes: 153
From: Nova Scotia, Canada
2019 SL450; 2023 M850i coupe
Software glitch? Intermittent electrical issues are always hard to track...
Hopefully it won't happen again, but at least if it does, it may be easier to track.
It probably triggered a code in XENTRY. But without a way of reading the chassis code that wont help...
Besides checking fuses and resistance/load testing main battery. There's a control module in the back that may be malfunctioning. That would be my first suspect, but may also be a bad ground.
Were both seats affected?
Good Luck
Hopefully it won't happen again, but at least if it does, it may be easier to track.
It probably triggered a code in XENTRY. But without a way of reading the chassis code that wont help...
Besides checking fuses and resistance/load testing main battery. There's a control module in the back that may be malfunctioning. That would be my first suspect, but may also be a bad ground.
Were both seats affected?
Good Luck
Yes, both seats were affected.
Where exactly is the control module located? I'd like to reseat that connector.
According to the fuse chart that came with the vehicle, there are 6 seat related fuses:
4 in the panel behind the passenger seat, and 2 in the panel in the drivers left foot well.
The chart does not specify which circuits the fuses protect.
I should have mentioned this in the first post:
After the car sat for an hour or so, I reseated--the original fuse was good-- one of the two 30 amp fuses in the panel behind the passenger seat. After that, everything worked again. The fuse in question, and the other 3 seat fuses in that panel, were dry and free from any corrosion.
The other 2 seat fuses, located in the drivers left foot well panel, were too difficult to access so I didn’t check them.
A MB Rep. and personal friend said it’s not unheard of for electrical glitches to reset after shutting down the vehicle and/or opening and closing the driver's door.
I just checked again today and everything is still working.
Rethinking my decision to not get an extended warranty.
Last edited by hornethandler; Mar 23, 2023 at 03:35 PM.
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From: Nor-Cal
2020 GLC300 -2014 Sl550 - 1997 SL600
Then it's most likely not module issue, as they are independent, one for each seat.
see attached pdf's
Pulling fuses could have reset the system. As you're obviously aware, sometimes even pulling fuses and reseating connecters is all it takes to fix an issue. Mild internal connector corrosion can be hard to spot. Problem with electrical issues, is you have to be patient and make only one change at a time. If you change 10 things, and the problem, goes away, it will be difficult to diagnose what the actual cause was.
Haha, if you work on planes you know, the software drives the hardware. Modern cars can have glitches, just like the software on a PC. Sometimes it needs a good reboot. I'm sure the car stored a code. XENTRY is helpful in giving clues to aid in isolating the potential culprit. Most cars I scan have a few "false" codes stored. Once reset, they don't come back.
I should have mentioned this in the first post:
After the car sat for an hour or so, I reseated--the original fuse was good-- one of the two 30 amp fuses in the panel behind the passenger seat. After that, everything worked again. The fuse in question, and the other 3 seat fuses in that panel, were dry and free from any corrosion. The other 2 seat fuses, located in the drivers left foot well panel, were too difficult to access so I didn’t check them.
After the car sat for an hour or so, I reseated--the original fuse was good-- one of the two 30 amp fuses in the panel behind the passenger seat. After that, everything worked again. The fuse in question, and the other 3 seat fuses in that panel, were dry and free from any corrosion. The other 2 seat fuses, located in the drivers left foot well panel, were too difficult to access so I didn’t check them.
Haha, if you work on planes you know, the software drives the hardware. Modern cars can have glitches, just like the software on a PC. Sometimes it needs a good reboot. I'm sure the car stored a code. XENTRY is helpful in giving clues to aid in isolating the potential culprit. Most cars I scan have a few "false" codes stored. Once reset, they don't come back.
Last edited by crconsulting; Mar 23, 2023 at 04:10 PM.
Thread Starter
Senior Member
Joined: Oct 2019
Posts: 293
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From: Nova Scotia, Canada
2019 SL450; 2023 M850i coupe
Then it's most likely not module issue, as they are independent, one for each seat.
see attached pdf's
Pulling fuses could have reset the system. As you're obviously aware, sometimes even pulling fuses and reseating connecters is all it takes to fix an issue. Mild internal connector corrosion can be hard to spot. Problem with electrical issues, is you have to be patient and make only one change at a time. If you change 10 things, and the problem, goes away, it will be difficult to diagnose what the actual cause was.
Haha, if you work on planes you know, the software drives the hardware. Modern cars can have glitches, just like the software on a PC. Sometimes it needs a good reboot. I'm sure the car stored a code. XENTRY is helpful in giving clues to aid in isolating the potential culprit. Most cars I scan have a few "false" codes stored. Once reset, they don't come back.
see attached pdf's
Pulling fuses could have reset the system. As you're obviously aware, sometimes even pulling fuses and reseating connecters is all it takes to fix an issue. Mild internal connector corrosion can be hard to spot. Problem with electrical issues, is you have to be patient and make only one change at a time. If you change 10 things, and the problem, goes away, it will be difficult to diagnose what the actual cause was.
Haha, if you work on planes you know, the software drives the hardware. Modern cars can have glitches, just like the software on a PC. Sometimes it needs a good reboot. I'm sure the car stored a code. XENTRY is helpful in giving clues to aid in isolating the potential culprit. Most cars I scan have a few "false" codes stored. Once reset, they don't come back.
Thanks for all the docs; I’ll give them a good look over.
I totally get the “change one thing at a time”. It was only after I reseated fuse #63 that everything came back to life. After that I reseated the other seat fuses as well for good measure.
Is there a document that shows the circuits individual fuses protect? It would be interesting to see what circuit is on the 30 amp fuse #63.
MBWorld Fanatic!
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From: Nor-Cal
2020 GLC300 -2014 Sl550 - 1997 SL600
I’m traveling for a couple of days so away from my shop. But in case you don’t have them, there’s a bunch of pdf’s in this thread which may also be helpful:
https://mbworld.org/forums/sl-class-...ml#post8237257
https://mbworld.org/forums/sl-class-...ml#post8237257
Thread Starter
Senior Member
Joined: Oct 2019
Posts: 293
Likes: 153
From: Nova Scotia, Canada
2019 SL450; 2023 M850i coupe
I’m traveling for a couple of days so away from my shop. But in case you don’t have them, there’s a bunch of pdf’s in this thread which may also be helpful:
https://mbworld.org/forums/sl-class-...ml#post8237257
https://mbworld.org/forums/sl-class-...ml#post8237257
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Thread Starter
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Joined: Oct 2019
Posts: 293
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From: Nova Scotia, Canada
2019 SL450; 2023 M850i coupe
Crconsulting, thanks for your help and for all the docs! The fuse numbers are not labeled on the actual fuse block or in the manual, so the docs. were very helpful.
Turns out the fuse (#63) I reseated was for the Airscarf Control Unit. So, reseating that fuse was not the reason the Active Multicontor Seat functions started working again.
Still at a loss as to why the seat functions stopped while driving, and then started working again after the car was shut down for an hour or so.
I’ll keep a close watch on the system and report back with anything conclusive.
Turns out the fuse (#63) I reseated was for the Airscarf Control Unit. So, reseating that fuse was not the reason the Active Multicontor Seat functions started working again.
Still at a loss as to why the seat functions stopped while driving, and then started working again after the car was shut down for an hour or so.
I’ll keep a close watch on the system and report back with anything conclusive.
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Thread Starter
Senior Member
Joined: Oct 2019
Posts: 293
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From: Nova Scotia, Canada
2019 SL450; 2023 M850i coupe
Well, it happened again today. All Active Multicontour Seat functions--on both seats--stopped working near the end of a 1.5 hour drive in the country.
However, this time everything started working again immediately after shutting down and restarting the vehicle.
I'm still under OEM warranty so will try to book an appointment and have the codes read.
Once I get more info I'll post an update.
However, this time everything started working again immediately after shutting down and restarting the vehicle.
I'm still under OEM warranty so will try to book an appointment and have the codes read.
Once I get more info I'll post an update.
MBWorld Fanatic!
Joined: Feb 2021
Posts: 1,419
Likes: 739
From: Nor-Cal
2020 GLC300 -2014 Sl550 - 1997 SL600
Well, it happened again today. All Active Multicontour Seat functions--on both seats--stopped working near the end of a 1.5 hour drive in the country.
However, this time everything started working again immediately after shutting down and restarting the vehicle.
I'm still under OEM warranty so will try to book an appointment and have the codes read.
Once I get more info I'll post an update.
However, this time everything started working again immediately after shutting down and restarting the vehicle.
I'm still under OEM warranty so will try to book an appointment and have the codes read.
Once I get more info I'll post an update.
. Usually solder or some passive component in the modules (just like any computer component) fails after some it gets some heat in it.I would hook it up to XENTRY and get any clues stored there. At least it will give you a starting point....
Good Luck
Last edited by crconsulting; Apr 13, 2023 at 06:33 PM.
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From: Europe, but from Norway
89 SL500 Silver ,97 SL500 Carlsson 04 Mercedes SL55 AMG , 07 Mercedes SL55 AMG convertedBlack series
Well, it happened again today. All Active Multicontour Seat functions--on both seats--stopped working near the end of a 1.5 hour drive in the country.
However, this time everything started working again immediately after shutting down and restarting the vehicle.
I'm still under OEM warranty so will try to book an appointment and have the codes read.
Once I get more info I'll post an update.
However, this time everything started working again immediately after shutting down and restarting the vehicle.
I'm still under OEM warranty so will try to book an appointment and have the codes read.
Once I get more info I'll post an update.
Thread Starter
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Joined: Oct 2019
Posts: 293
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From: Nova Scotia, Canada
2019 SL450; 2023 M850i coupe
When the seats are working you can hear the pump and feel the seats respond.
Massage was not turned on when the system stopped working. I was only using the active side bolster at the time; however, all Multicontor seat functions stopped working.
Observations:
The seat adjustment (massage on/off, lumbar and side bolster) changes are correctly indicated on the Command Control Unit (display); however, neither seat responds and the pump cannot be heard.
Also, seat position (lumbar and side bolster) indications go to “0”, and the massage “On” indication switches to “Off”, when the control (Command Controller switch) is released.
From what I can determine from the docs. provided by crconsulting, the only common component--besides the Command Control Unit--to both seats is the seat pump.
It would be interesting to see if the pump is receiving signals. I assume it would be pretty easy to check.
Does anyone know where the Active multicontour seat pneumatic pump (code # M40/1) is located?
Last edited by hornethandler; Apr 15, 2023 at 10:34 AM.
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From: Nor-Cal
2020 GLC300 -2014 Sl550 - 1997 SL600
It's in the trunk. This may help:
https://www.mercedesbenz.parts/v-201...-and-connector
There are also some components to that system in the seat itself.
Thread Starter
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Joined: Oct 2019
Posts: 293
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From: Nova Scotia, Canada
2019 SL450; 2023 M850i coupe
It's in the trunk. This may help:
https://www.mercedesbenz.parts/v-201...-and-connector
There are also some components to that system in the seat itself.
https://www.mercedesbenz.parts/v-201...-and-connector
There are also some components to that system in the seat itself.
Is that the same pump that operates the soft close doors?
MBWorld Fanatic!
Joined: Feb 2021
Posts: 1,419
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From: Nor-Cal
2020 GLC300 -2014 Sl550 - 1997 SL600
Thread Starter
Senior Member
Joined: Oct 2019
Posts: 293
Likes: 153
From: Nova Scotia, Canada
2019 SL450; 2023 M850i coupe
It's in the trunk. This may help:
https://www.mercedesbenz.parts/v-201...-and-connector
There are also some components to that system in the seat itself.
https://www.mercedesbenz.parts/v-201...-and-connector
There are also some components to that system in the seat itself.
I'll take a look at the pump to see if there's any way to monitor the electrical signals to the pump to determine if it's the pump, or the command signals to it.
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Joined: Feb 2021
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From: Nor-Cal
2020 GLC300 -2014 Sl550 - 1997 SL600
Thread Starter
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Joined: Oct 2019
Posts: 293
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From: Nova Scotia, Canada
2019 SL450; 2023 M850i coupe
The snag has only happened on two separate occasions, and only after over an hour of driving time, so I'm preparing for what will most likely happen:
MB will claim "no fault found" and I will end up trying to fix it myself.
There's another reason, though... there's a lot of great folks and knowledge on this forum, and I just enjoy sorting out problems.
Last edited by hornethandler; Apr 16, 2023 at 09:29 PM.
Thread Starter
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From: Nova Scotia, Canada
2019 SL450; 2023 M850i coupe
For anyone who’s following, here’s an update on the snag.
In an effort to duplicate the snag, I electrically disconnected the seat pump in the trunk. It has one 4 pin connector with two large, and two small diameter wires.
According to the Electrical Function Schematic, I’m guessing the two large wires power the pump motor, and the two smaller wires transmit/receive the status/request signals to control pump operation.
Observations
The symptoms with the connector disconnected are exactly the same as when the snag occurs:
“The seat adjustment (massage on/off, lumbar and side bolster) changes are correctly indicated on the Command Control Unit (display); however, neither seat responds and the pump cannot be heard.
Also, seat position (lumbar and side bolster) indications go to “0”, and the massage “On” indication switches to “Off”, when the control (Command Controller switch) is released.”
So, one way to duplicate this exact snag is to disable the status/request signal at the seat pump in the trunk. I’m only guessing that it’s the status/request signal, but it could be that the whole pump assembly was electrically disconnected.
For now, since that connector has been reseated several times, I’ll drive the car and see how things go. Hopefully it was a little corrosion on the connector, I have my doubts, but hopefully.
In an effort to duplicate the snag, I electrically disconnected the seat pump in the trunk. It has one 4 pin connector with two large, and two small diameter wires.
According to the Electrical Function Schematic, I’m guessing the two large wires power the pump motor, and the two smaller wires transmit/receive the status/request signals to control pump operation.
Observations
The symptoms with the connector disconnected are exactly the same as when the snag occurs:
“The seat adjustment (massage on/off, lumbar and side bolster) changes are correctly indicated on the Command Control Unit (display); however, neither seat responds and the pump cannot be heard.
Also, seat position (lumbar and side bolster) indications go to “0”, and the massage “On” indication switches to “Off”, when the control (Command Controller switch) is released.”
So, one way to duplicate this exact snag is to disable the status/request signal at the seat pump in the trunk. I’m only guessing that it’s the status/request signal, but it could be that the whole pump assembly was electrically disconnected.
For now, since that connector has been reseated several times, I’ll drive the car and see how things go. Hopefully it was a little corrosion on the connector, I have my doubts, but hopefully.
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Good Luck.
Last edited by crconsulting; Apr 20, 2023 at 12:46 PM.
Thread Starter
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Joined: Oct 2019
Posts: 293
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From: Nova Scotia, Canada
2019 SL450; 2023 M850i coupe
I think as you surmised in the post #17, since it was both seats, it was most likely something common to them.
Exactly...
I've repaired several electrical "problems" this way. But success rate is low.
You should note the mileage and date in which you did that. When the tech scans the car with XENTRY, it will probably have stored a code for this event. You don't want an inexperienced tech to come back with the quick diagnosis of replacing the the pump if it's not the issue. Hopefully that information can be communicated to him directly, as things are often "lost in translation" when going thru the service writers.
Good Luck.
Exactly...
I've repaired several electrical "problems" this way. But success rate is low.
You should note the mileage and date in which you did that. When the tech scans the car with XENTRY, it will probably have stored a code for this event. You don't want an inexperienced tech to come back with the quick diagnosis of replacing the the pump if it's not the issue. Hopefully that information can be communicated to him directly, as things are often "lost in translation" when going thru the service writers.
Good Luck.
I will note the date and Km I disconnected the pump and advise the service dept. I’m hoping to talk to the tech one-on-one to give them details of the snag, and what I did.
In my experience it’s a delicate line as you don’t want to come across as telling them their business. Technicians are much like artists... they're sometimes very protective of their craft.
Last edited by hornethandler; Apr 20, 2023 at 03:26 PM.
Thread Starter
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Joined: Oct 2019
Posts: 293
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From: Nova Scotia, Canada
2019 SL450; 2023 M850i coupe
Update for those following:
The Mercedes tech identified a very slow leak in the drivers’ side Backrest Sides (inflatable bolsters). The leak is in the inflatable bolster itself and not in the air line.
Mercedes uses a pressure/vacuum tester--similar to an aircraft pitot static tester--to pressurize and to pull a vacuum on the inflatable seat components to check for leaks.
The tech explained that the reason the slow leak caused an intermittent failure in all Active Multicontour Seat functions in both seats, is because when a leak is detected, the Seat Pump Motor shuts down to protect itself from overheating. The pump then resets after a period of time.
The inflatable bolsters come as a set, i.e., each seat has two, and cost around $300.00 CDN; I have an appointment on 26 Jun. to have them installed.
I’m still under warranty so will let them do the job; however, according to the tech, it’s not too difficult a job to R&R the inflatable bolsters. If that’s the case, I’m thinking a simple bicycle tire repair patch will do the job if it ever happens again.
Hopefully all goes well and I'll report back to confirm the fix.
The Mercedes tech identified a very slow leak in the drivers’ side Backrest Sides (inflatable bolsters). The leak is in the inflatable bolster itself and not in the air line.
Mercedes uses a pressure/vacuum tester--similar to an aircraft pitot static tester--to pressurize and to pull a vacuum on the inflatable seat components to check for leaks.
The tech explained that the reason the slow leak caused an intermittent failure in all Active Multicontour Seat functions in both seats, is because when a leak is detected, the Seat Pump Motor shuts down to protect itself from overheating. The pump then resets after a period of time.
The inflatable bolsters come as a set, i.e., each seat has two, and cost around $300.00 CDN; I have an appointment on 26 Jun. to have them installed.
I’m still under warranty so will let them do the job; however, according to the tech, it’s not too difficult a job to R&R the inflatable bolsters. If that’s the case, I’m thinking a simple bicycle tire repair patch will do the job if it ever happens again.
Hopefully all goes well and I'll report back to confirm the fix.
Last edited by hornethandler; May 18, 2023 at 04:06 PM.
