I have a Mercedes-Benz S500 W221 equipped with the Distronic Plus option, but the Cruise Control function rarely works. In most cases, when I try to activate Cruise Control, a yellow warning message appears on the dashboard stating “Distronic Plus Inoperative”, or sometimes the Dis + Km/h flashes as shown below.

I have checked the radar sensor and the Distronic system and found no fault codes. I am also confident that the issue is not caused by external interference.

I have checked the ESP module and the Steering Column Module as well, and both appear to be functioning normally. The Parktronic system, which also relies on radar sensors, is working correctly.

At this point, I am starting to suspect that the problem may be related to software or coding/configuration, but I am not sure where to begin troubleshooting.

I would appreciate any advice or suggestions from those who have experience with this issue. Thank you in advance.


Some time ---Km/h is flasing and them DisPlus disapear



Most of time ai get this error

 

will have a think - but its pretty robust - had mine 12 years it the only bit that works reliably in the entire car - lets hope is not as simple as this bit.....

Dis + Km/h flashes - is you, read the manual - "Can't instigate ANY cruise set speed, till you are travelling above 20 mph (about 30 kph)". Once above that you can set any speed you like (from any current speed) and it will manage as fast as that and all the way to stopped in traffic. If the stop is almost imperceptible it will just drive on when clear. If its stops dead for more than say 1/2 a second it will sit doing nothing with the brakes on (in case you fell asleep) - you can override and drive with cruise cancelled if you apply the throttle - OR - when it clears ahead, it will allow you from Stationary to "Resume" cruise control assistance up to as fast as traffic in front allows, until it again reaches your last set speed (if the gap to traffic ahead is enough). You do this Resume from rest by flashing (pull towards) the small cruise set stalk.

If you have an ABS wheel speed sensor failure or misreading on any of its four road wheels (common !!!) cruise will not operate

I suspect its insufficient road speed to set - and then a part broken ABS sensor - if the later you may notice the auto park brake is strange and beeps more often

 

If it's showing a fault message on the display, there's going to be a code somewhere.

There's 2 ECUs for Distronic plus... 1. The main Distronic unit behind the grill. 2. The Plus part in the right hand back corner of the trunk.

It also interacts with the Steering Column module, ESP/ABS, ISM and TCM and finally the engine module.

The issue could be anything from a loose plug to a failed sensor.

Any recent work done?

What code reader are you using?

 

I'm using Star C4 diagnostic, with Dis + Km/h flashes even the car at speed 70-80km/h.

Will investigate ABS sensor to see if any link to Cruise Control inoperative

 

ABS sensors are the only way the car knows its moving, at what speed and in what direction. As ESP and ABS can not function without good data from every wheel speed sensor - Cruise Control is always disabled without them

The Electronic Park Brake uses the same data for Auto off. As does ISM for Auto Park position. And so does variable rate Power steering assistance - so one popped ABS sensor can make for No gear selection, no ABS, no ESP, no Cruise control, odd Park brake and heavy Power steering

 

In which case there will be a code.

Rather than fiddlearsing around with a handful of straw, do a complete vehicle scan and work your way down the list. Erase each code as you go, then rescan the car and see what comes back and investigate accordingly.

And report back.

It's not an ABS fault. If it was the yellow message would be ESP/ABS unavailable.

 

on my original ABS sensors (different part numbers) my left rear stayed part functional for 6 months and NEVER threw any messages at the screen - at first it only impacted the performance of the Park Brake and gave extra bings (which was i now realise to inform you it let itself off uncommanded),

mate with the CL500 used his with intermittent operation for 2 1/2 years

when that first one, left rear finally died - I replaced all 4 with updated merc part number sensors - two of those have died (in less than 20k miles of use) both immediately throwing ABS ESP message and giving ISM gear selection fun. A very different failure mode to that first one without an error message for 6 months

 

Your car is definitely a Friday afternoon special...

 

talking at length with mate with CL500 (built june 2009) he's super fussy and was just told the extra 25k GBP a CL buys you better paint work and posher trim levels - so no one wants to do bodywork as its too difficult on a CL - but the point of this response is to say his is way more troublesome than mine - but everything I read on this forum and have for 8 years matches almost to a T issues he and I get all day long - note his was only ever worked on by posh main dealer from new

 

The car had its Steering Columm Module replaced with a used SCM taken from a US-market S550. Therefore, although the steering column switch on my car has the Speed Limit switch, the Speed Limit function does not work because the US-market SCM does not support the Speed Limit option.

All other SCM functions are operating normally, so I believe the “DIS Plus Inoperative” issue is not caused by the SCM.

I still do not know the root cause. Sometimes there is a yellow warning on the dashboard, while at other times “DIS Plus — km/h” flashes. However, when reading faults from the control modules, everything appears completely normal.

For some reason, it seems that the control modules are not communicating properly with each other, yet no error codes are being generated. I will further check the Radar and Distronic modules, and if necessary, I will try replacing the Central Gateway.

can you help to check ESP with the firrmware 2219029502 is for M273 RWD? I plan to flash ESP with current fw (see below) to 2219029502 version.

 

kept that quiet

there is something like two SCMs a budget nasty for simple cars and a real one for distronic plus - have you got steel wheel heater they need the good one - although to hot for it to switch on in summer - but light on stalk may light if you twiddle it

 

When I started to read this thread the first thing I thought was the CGW. Just disconnect-reconnect the harness as it can change things.

CGW is poorly made with unsoldered pins at the harness connection. I soldered mine and it took care of a bucket full of error codes but there was no error for the CGW itself.

Easy fix to try.

 

OK so there is a speed limiter feature on my car - why ? the distronic plus does all that and more ???

you def have the distance to car in front gap lever like this ?

 

Finally, the real reason why it doesn't work...

To clarify, the SCM includes the shift lever and cruise stalk...
Your original one is Distronic with the limit function (yellow light when you push the end of the stalk in).

Is the new one the same part number? And does it have the same stalk functions?

Go into CGW and make sure the box for Distronic Plus (233) is ticked.

Do the same in the SCM.

Also make sure the Speed Limiter box is ticked if your stalk has the function. Untick it if it doesn't..

That should sort it.

In live data in the SCM it should show the limit switch operating as you press it if it's fitted.

 

Despite SCM does not support LIM (yelow lamp) when press in however I can read the live data about distance to car in front gap lever of the SCM and Distronic Plus is works for a while with this SCM then the SCM without Speed Limit might not a culprit.

i will try to get the right SCM to test and will resolder CGW box.

 

Perhaps after SCM replacement, we need to drive long distance at high speed for distronic module calibration angle sensor.


despite that the replaced SCM does nit support speed limit function however distance potentiometer switch still works properly then I don't think SCM is culprit


Check Distronic module ai realized that steer angle correction is not programmed

Perhaps long distance on the highway will make Distronic Plus works?

 

CGW you'll need leaded low temp solder to make a safe go of it - its another multilayered board of hell - that eats all the temps, and std junk solder will just trash the board - and if you trash fully car will not work every again - and coding that at home will make you think everything you have ever done before look simple - plus service history !

 

Driving to the moon wouldn't make it work.

You have 2 actual issues.

1. In SCM go to Development Data. Select variant coding and make sure limiter is set to On/Ein. Save and Exit. Double check all the other functions on your column as factory optioned.

2. The steering wheel position is not what the SCM is expecting. Probably because the wheel was catywampus when you switched SCMs. Or you refitted the clock spring on the ****.

It may be possible to recalibrate the SCM. This is probably in actuations.

The wheel position shouldn't affect the Distronic function as that radar is fixed and not influenced by steering angle.

If any of this is out of your comfort zone, consider it a lesson and learn from it.

Neither of these codes or the issues you are experiencing have anything whatsoever to do with ABS sensors or the CGW. Do not be distracted by noise.

 

once upon a time (2019) with legit online xentry and then of course SCN coded online - I had ABR updated, DTR updated (it didn't take it first round and had to try again), and then the SGR radars which took 5 attempts to accept the new software version, each time a progress bar got a bit further - ever since they have all worked reliably, and in virtually the same way, and never thrown an error code (other than the parking sensor fun with other car brands sending drivel it doesn't like)...

There are a few exceptions

1) (I forget which module asked for a setting input, but most likely the DTR) - and sadly I have never found the setting again - post programming one of these three asked a user preference set up question - Std (which may have been 120m, or the 180m as you shown in the SCM module picture above!!! ) or Shorter range. As I was hoping for it to cope better in traffic we selected the shorter distance. Round town radar performance remained exactly the same - AKA slightly incompetent in stop start traffic - where it still tries to launch off the line to hit at least 20 mph - even if the traffic and distance ahead means 7 mph would have made sense !

This bad behaviour in traffic, can be managed by having the gap setting at two back from closest - were its usable with comfort suspension, which brings 2nd gear pull-away, and thus the car cope in dense traffic. Note another change - from mid 2007 Rear SAM update, they changed the lead foot launch throttle application so its less awful below 40 mph - but it then becomes dangerous on the open road (where is slower than grandad)...

2) The post update setup question Xentry posed, in whichever module it was, away from Merc recco - seemed to transform its ability at higher speeds on slip roads - where ever since unlike the software the car came with - the updates and or that setting change means its far happy to never notice the traffic stopped at the end of the slip road and would rather try its luck hitting them at 70 mph, than the old days where it gently braked.

3) other than that undesirable change - one other bit of incompetence that came with the Rear SAM updates - is its new very irritating cruise disable feature if the fast wipe operates continuously for greater than X. I had driven this car for years using active cruise in extreme wet weather, many, many times and it never once had a moment or seemed it couldn't cope. Indeed it was actually safer as it found cars you struggled to see due to rain. Now on the recco (forced) Rear SAM update of 2010 its ridiculous and just offensive. Going backwards on software to mid 2007 its far less offensive. Whilst OEM was perfect.

anyway @ AL5461 - I wonder if that parameter 20 in the SCM saying 180 is the same in my car - seems really odd if that’s the 1) bit I mention above - as we never touched it and its software version is not updatable...

 

steering angle does impact Distronic Plus performance

another change in the later SAM software

OEM Rear SAM software on the earlier cars (pre 2007) had quite distinct throttle off, and then if it was still getting nasty, braking based on steering angle input. Still on it, it would rein it all in. Going into a tightening bend it was obvious the car would take quiet significant action to reduce speed. As first it was disconcerting as never once noticed it on my BMW 335 with active cruise. But once you knew it did it - it was actually sensible (like all the original software on the 2006 cars - rather than the part backed madness the young morons threw at the cars with each 2008, and then late 2009 facelifts).

The tighter the bend (more steering angle applied) the more the car stopped it flying at corners. Any of the 2007 and then 2010 Rear SAM updates seemed to totally disable the feature. But I now realise its just about there.... its as if the new engineers didn't realise it was sensible and the old boy knew if the bend catches you out and then grip levels were to go south at the same time - it might as well manage the mess

I suspect the last updates were badly developed - youtube clip showing a facelift W221 vs a Volvo with ADAS- Every test the Merc crashed, same test the Volvo passed easily. Top gear even had a pop about it - although never public I believe Merc rushed around trying to cover it up....

the top gear Micky-take with excerpt of Merc's testing

 

I can't find any coding option of the SCM under development data then therefore activation of speed limit is not possible, however I will check it again.

what parameter to tell you that steering wheel position is not what the SCM is expecting? I íntalled steering angle sensor and clock spring and no way by mistake, perhaps steering angle sensor need to be calibarated?

 

I have not read all the posts, so this may already have been discussed. SOMETIMES, the radar sensors used for PRE-SAFE and DISTRONIC PLUS fall out of calibration. There is a simple procedure to recalibrate the radar by driving about 15 minutes if you have XENTRY or a Mercedes-specific scan tool like LAUNCH X431 Creader Elite V1.0 (2.0 or 3.0) BENZ (or whatever name they use now). Here’s the discussion from @JettaRed

There is a full explanation and instructions on how to initiate calibration using either XENTRY or LAUNCH.

https://mbworld.org/forums/sl-class-...m_content=post

 

I have found sometimes the drivers in front of me are being too reckless, tailgating the car in front of them while driving 70 mph or more on the highway. While DISTRONIC PLUS is very effective at keeping the distance, I just feel more comfortable widening the distance to the idiot in front of me. And it usually makes my passenger more comfortable, as well. Then there is the situation of wet road vs. dry road. Having a few more seconds of stopping time and distance is nice. I like that you can adjust the gap for different driving situations.

 

I like that you can adjust the gap for different driving situations.

 

that’s why it's there - it would be sensible - but manufacturers are too dim to think of sensible stuff - to link the gap to the rain sensor - sees rain 3.0 second rule, heavy rain 3.5 seconds, no rain 2.0 second rule. Or even 2.5 seconds in comfort and 1.9 seconds in sport etc. Add that feature to an auto gap and it can be a user choice within the current preset gap adjustment we've already got

if you follow the points in my posts above - two clicks back from closest, allows the car to manage slow speed congestion (1 to 15mph) without the kangaroo petrol effect

I have a point 4) the early software in that Rear SAM had road rage cruise kick-down when using in sport

comfort setting - cruise set point 85mph, road speed due to traffic 83mph - car in front moves car increases speed
sport setting - cruise set point 85mph, road speed due to traffic 83mph - car in front moves smash it down a gear, bury the throttle, overshoot setpoint....

got to love Germans terrorising autobahns

I have used the speed limit function once in my fathers merc - its pure dangerous madness - need to go quicker and the car won't respond - panic - as death looms nail the kick-down for dear life car realises the danger and allows speed to increase - lets hope there enough time to remain alive !!!!!!!

Whereas with active cruise, set the max speed (to suit ave distance speed cams etc.) car will safely navigate anywhere between zero and that setpoint - need to go quicker, override with a smidge of throttle, get safe, back off, car brakes to set speed