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Hi everybody! I've just get '08 SL63 with 46k km on the clock in very good condition despite one annoying issue: gearbox (722.930) randomly switches to manual mode instantly dropping 1-2 gears.
It is more often while motor oil temp is below optimal (blinking number on dashboard) both during driving or waiting at traffic light, but also randomly occurs on properly heated transmission either during driving on motorway using Distronic or acceleration. Worth to mention that wheel shifting paddles are not working correctly due such downshifts: UP switches to lower gear while DOWN doesn't do anything. At the same time, gear lever shifts up/down as usual.
No errors are detected via diagnostics tool.
Does this issue looks familiar to anybody? Any suggestions for further diagnostics/repair?
There were posts on this recently; their issue was with the paddle module on the wheel; might have been as simple as cold solder joints but it didn't sound too hard to remove the module, inspect it, repair it or replace it with a newie. Search is your friend.
There were posts on this recently; their issue was with the paddle module on the wheel; might have been as simple as cold solder joints but it didn't sound too hard to remove the module, inspect it, repair it or replace it with a newie. Search is your friend.
Thanks, have found that either the entire steering column switch assembly or steering column control module should be replaced. The latter one could be found new (A0335456232), while the assembly only available as used.
Just for curiosity, what is the issue with that module?
I'll bet it's a connection, cold solder or break in a track somewhere. I haven't seen one but I'd be having a good look at it under a mag light first before ordering a replacement. Random failures are very often caused by mechanical failures on the board somewhere. Semiconductors and passive components usually fail definitively, rather than intermittently, as with your symptoms.
Currently hard to tell: mechanics have spent another day at the garage and insist on replacing front-right SAM module due to saved error they have found (error code B1000).
Now I'm wondering:
1) if A2305454532 could be replaced with the latest revision of this item A2309001600
2) should I insist on replacing SCU - it's not readily available neither used or new
Looks like the issue somewhere in wheel paddle shifters - my mechanics have found that electrical disconnection of the shifters heals random shifts. Now the goal is to locate exact location of this fault (it still could be in SCU), but due to the lack of replacement module it will take a while. Hope that this temporary solution will have no side-effects
The SCU is inside the steering wheel, so look for a cheap wheel, and check module is still in it. Noted on eBay a lot of wheels have the SCU removed (where have they all gone!!) but quite a few still show the SCU fitted.
The SCU is inside the steering wheel, so look for a cheap wheel, and check module is still in it. Noted on eBay a lot of wheels have the SCU removed (where have they all gone!!) but quite a few still show the SCU fitted.
Thanks, it appeared that gear shift control unit (N135) is mounted on the airbag module and can't be ordered separately (A033481402). N135 on the driver's airbag
But the main problem is that even switching off the N135 (which desables all the buttons on the wheel including horn) doesn't solve main issue. Actually, it solved it for some time, I've been able to make a few km ride around without any manual\downshifts. But after 1-hour stopover the damn thing has returned!
Now 3 ECUs are under suspect but the problem is that order lead time for them are quite unpredictable. In the meantime will check gearbox oil condition.
Thanks, it appeared that gear shift control unit (N135) is mounted on the airbag module and can't be ordered separately (A033481402).
A quick look at your electrical wiring diagram says something different!
N135 is the steering wheel switch controller, and has nothing to do with airbags! It just converts the wheel switch signals to CANBUS and receives a power feed.
The airbag ignition wires pass straight through the squib to N2/7 the SRS controller. Airbags would never use CANBUS
It looks like the module is part of the steering wheel, and not available separately!
The part number you gave appears to be a digit short! normally "A" followed by 10 digits. First three digits, usually a model designation, such as 230, 171, 209 etc.
Just noted there is a difference on earlier cars, but they do not have an N135 module. If you give age, or VIN number (I am assuming it is 2008 facelift), I can give correct schematic.
A quick look at your electrical wiring diagram says something different!
N135 is the steering wheel switch controller, and has nothing to do with airbags! It just converts the wheel switch signals to CANBUS and receives a power feed.
Correct, I've just said that it attached to airbag and can't be sourced separately (as per spare parts catalog)
Originally Posted by g0rsq
The part number you gave appears to be a digit short! normally "A" followed by 10 digits. First three digits, usually a model designation, such as 230, 171, 209 etc.
Exactly, according to the picture above it has only 9 digits which is quite surprising.
Originally Posted by g0rsq
Just noted there is a difference on earlier cars, but they do not have an N135 module. If you give age, or VIN number (I am assuming it is 2008 facelift), I can give correct schematic.
Hi Didn't realize your car was 2002!
I enclose relevant electrical drawings for gear selector on AMG steering wheel.
Wiring from switches, goes straight through squib, Steering column module to the gear selector module. They are not on CANBUS, nor can I see any connection with Airbag system!
Note the switches seeS111/1 and S110/1 seem to be drawn wrong! I can only guess they are normally closed switches, otherwise the circuit cant work for shifter +
Looks like 3 voltage levels depending on which switch is operated.
Feels like we've got final solution for this issue: front passenger SAM (A2305454532 which was there since production date) has been replaced with brand new (well, factory refurbished in reality A2309001600 80) followed by rear battery.
All the symptoms has gone so far (fingers crossed). The only mystery for me is how this hasn't been solved for the last 7 years by official dealers? Based on data I have, they have tried to find solution since 2015 and nobody suspected SAM module (given some non-current errors with it in the past)
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