Last week ABS light came on (07 S600)

Code reader indicated right front ABS wheel sensor was faulty so changed it.

ABS light went off initially but came back.

Now when I start the vehicle in the morning the cluster reads “ABS ESP Unavailable” but once I drive a few feet the light turns off.

After about 30 seconds the ABS light returns.

This occurs every time I start the car the ABS light is on initially, turns off when I begin driving then turns on again after about 30 seconds.

Today, I go to my Indy who scanned the car and got a U140900 code indicating the LEFT front sensor was “unreliable” (as noted above last week the issue was the right/passenger side).

I decided to call around and Napa had an aftermarket in stock so I grabbed it and swapped out the driver’s side sensor—Now the light is on continuously.

It no longer turns off at startup and turns back on—So I unplugged the sensor slightly so it was out of the housing and immediately the car screams “Park Assist Unavailable”

I reinserted the new sensor all the way and again, the ABS light just stayed on but now the “Park Assist Unavailable” warning was gone.

Just to see what would happen, I removed the new sensor and reinstalled the old one and now the ABS light turns off when I start the car and comes back after driving for about 30 seconds.

Anyone experience symptoms like this?

 

That's weird. I've never had this happen, but every time I get "ABS ESP Unavailable" it is fixed by driving around the block in 'Dyno Mode'.
Try that and see what happens.
https://mbworld.org/forums/s-class-w...ml#post9078813

 

oh yeah! I did that a few years back on my other car and it did turn the light off!

will give it a try in the morning!

thanks

 

all you need to do is see if you have comms with the ABS module - no comms usually means as designed the module is dead

if you have comms - go to live data and drive as you look at wheel speed readings - if these relate to driving conditions and all four seem reliable, its likely nothing is wrong

if one of the rears is showing unresponsiveness, expect gearbox selection problems as the ISM gets muddled. plus ESP ABS message
if a rear is intermittent expect park brake problems and extra bings and bongs, plus ESP ABS message
if a front is wrong its more likely to just upset the ABS, still expect ESP ABS message

don't forget ESP runs off the very same ABS sensors and needs all fours wheels to make sense, alongside the steering wheel angle sensor and throttle setting / use

the front sensors run off the inner wheel bearing seals that will pick up brake dust and debris and build up a layer of magnetic gunk you can’t see or clean without removing the front hub - this may impact sensor performance

the rear sensors run off a reluctor ring on the rear hub / drive shaft, it can corrode and misread or even fall off

After dead ABS modules (that afflict Ford and Merc far less than BMW or VAG because they buy the better spec modules with greater clearance on the ESP pump motor brushes), its the IPC chip at the end of the sensor just failing one day. Its job is to amplify the weak signal from its interaction with the reluctor ring. The more confusing failure mode is a break in the sensor wiring - this again is a normal failure mode on many brands - as they deliberately route to make the wires snap - the more stress raisers, the more acute the bend, and the worse the routing to get suspension travel stressing one spot the better. This failure mode can exist for 6 months to a year before giving op entirely - and often first gets triggered by a large pothole.

Merc state to swap axel sensors in pairs (sensible given wire breaks and IPC chip ageing failures) - don't forget failed ABS sensors, runs along side V12 coil packs, as the most common failure modes on the 221 - the dyno thing is the biggest load of **** I ever heard


.

 

re the other misleading post today (confirming dyno mode fixed the car)... ABS ESP can't invent being muddled - and whilst rare events can introduce the need for the vehicle to successfully complete the "road test calibration of the ESP system" Dyno mode certainly can't fix anything - but maybe this car instigated procedure can trick the car into a quick sensor check ?

Dyno mode I believe is just "children's mode disabling traction control and ESP completely" - so it shouldn't be able to fix or reset anything - I guess it might be that using this "toy" informs the car play time is enabled and the ESP module is about to be fed utter garbage - so the car knows when switched off (key on off cycle), it needs to briefly sense check info coming from the ABS wheel speed and Steering angle sensors.

Which bring me back to fixing things - ESP becoming muddled can happen from significant misinformation from wheel speed sensors and steering angle data telling the car something is wrong - so if you set wheel geometry way out and drive the car it can bring in the ESP calibration need - as can weird CAN signals being bounced around the car (say if diagnostic tool developers are stealing info from a breakout box - at the same time as using Xentry to look about at what various systems do). I have been there in both these situations and have found and witnessed others trying to get the car to accept completion of the "road test calibration" is irritating (with lots of full lock to full lock back and forth maneuvering and failed attempts... ).

So where this dyno magic cure seems to have worked - I would suggest you really have failing wiring in one or more ABS wheel speed sensor - had a mate with his CL500 keep paying monkeys to reset his ABS error messages for two years before he believed me and replaced his rear sensors - and ever since no more problems

 

——-Update——

Recently drove in dyno mode for 2 days (about 80 miles).

The following changes occurred:
1) The park assist sensors have started beeping again at startup

2) Night assist is no longer available

3) Pulsation when braking is almost nonexistent vs it feeling like a warped rotor before

4) The distance display is functional now and the car in front of me is being displayed

5) The ABS warning ⚠️ stays off a few seconds longer when first driving, evidenced by how much further I can drive from the garage to certain landmarks near the house.

*the fault is being identified as the front left wheel speed sensor (which was replaced with MB part purchased in person from the stealership)

*once the brand new sensor was replaced the ABS warning ⚠️ light just stayed on upon start up.

*old sensor re-installed and now the ABS warning ⚠️ light turns off on startup and comes back on after driving for about 10-15 seconds.

—It’s as if with the old sensor the car is at least trying to communicate with sensor vs when the new one was installed the warning ⚠️ light just staying on seemed to suggest there was not even an attempt to communicate.

Any thoughts?

 

Has the car been plugged into XENTRY yet?

If not you are wasting your efforts via firing the parts cannon at the issue.

Botus has supplied a number of helpful insights; waiting to be gleaned if you can look past his classic jaded British snark.

 

“The classic British snark”🤣🤣🤣 it’s a joy to read a Botus comment and while confusion occurs I imagine a Monty Python skit and it still seems worth it!

But as mentioned previously had my Indy pull codes (Autel) : U140900
*Front left wheel speed sensor unreliable

Hoping with a clear description of what’s been happening someone recognizes the symptoms and can provide some insight.

The goal is to avoid throwing parts at it (i.e. Changing all wheel sensors or ABS control module)

 

Has the AUX battery been checked/changed?

That battery being too low will not allow ESP, ABS and Distronic to work in my 2010 E550.

This battery is a fist size battery in the driver's end of the dash. I don't know where and what size AUX battery an 07 S600 has but my 2012 S550 has the same small battery in the driver's end of the dash.

The car should give an error message about low AUX battery, but my car does not. The "message" is malfunction of said features.

 

I'd want to know the seal on the back of the front wheel hub is clean, undamaged and the correct part,
and that the sensor you replaced is the correct one - I think they have differences between early and later facelift cars

other oddness - Merc claim you need to replace sensors in pairs - it shouldn't have an effect - but then these are Mercedes and not entirely normal motorcars

of the list of Fun mentioned - the pulsation sounds to me like continuous ABS intervention - turn it all off and it stops (using dyno mode)

 

This is a great suggestion Arrie!

I’ll double check if there is indeed a AUX battery on this particular year (07) but I did wonder if the main trunk battery might be a factor🤔

I recently purchased a trickle charger that claims to both charge and repair the AGM main battery. Before the 12hr process the voltage was reading 11.7 while the car sat over night.

After the charge/repair it holds at 12.1 overnight and occasionally will drop to 11.9 overnight.

When I start the car it immediately jumps to 14+ volts so…

If there is indeed an AUX battery I definitely would like to explore its role in this issue.

 

Another source of ABS errors would be a worn out wheel bearing. On the back of the bearing is the ring that the sensor reads the signals from. If the bearing is worn out you will also hear rotation noise while driving.

 

I had the bearings checked and there was absolutely no play.

That said, would you happen to know if this ring is a replaceable part?

 

of course - I mentioned this in my first reply, the second and the third - the correct inner wheel bearing seal IS THE RELUCTOR that triggers the HALL effect in the IPC Amplifier at the end of the ABS sensor

 

Yes, cheap part and worth a try. The aux battery is cheap enough you might as well try that as well. Even if not 100% worn out parts, you are likely close so you'll be doing it soon anyway.

 

In DAS there is a procedure to click on to reset the damn thing. Forget what it is called, "recalibration" or something similar. It is about the only way.

When replacing the abs sensors, hose down the hole with brake cleaner...also cleans the sensor ring of crap.

 

The ‘trigger wheel’ the ABS sensor is looking for being built into the seal for front wheel bearings means that any crap that has collected on it will have just enough bearing grease on it that a rinse with brake cleaner isn’t the best. Pull the hub off with the rotor removed and there it is to see. At which point one can just yank that seal out; have a good look at wheel bearings, pack them with fresh grease and reassemble.... with a fresh seal.

 

I stand corrected, I should have specified rear ones.

 

By FPC Euro you have the same small AUX battery as I do in my 2012 S550. See the link below.

If you don't know the history of this battery, I recommend you replace it. It is located inside the driver's end of the dash. You access it via the footwell.

In my 2012 S550 the CGW is mounted in the same bracket with this battery.

http://www.fcpeuro.com/products/merc...y-000000004039

 

nope, sadly not - its magnetic gunk and can only come off wiping thoroughly - which means its got to be stripped down

rear - impulse ring part 120 - on an early 221 071

120 IMPULSE RING LEFT 001 A 23 035 701 82 - $10.82
120 IMPULSE RING RIGHT 001 A 23 035 701 82 - $10.82

 

Ahhh.... I stand corrected.

 

I dont think a 2007 S600 uses this auxillary battery. I could be wrong....

 

Sure seems like I got to replace a start battery in the 221 S-65

 

Ok great! Thanks for confirming Arrie!

I was able to find a video of the AUX battery replacement:

 

BOTUS thank you for clarifying!

You very well may have said this before but I’m far from clever enough to keep up with the charming British banter and end up missing the info all together🤣

The link you provided for the parts led to a random page for a parts dealer but the part# don’t correspond to any MB genuine part #

If possible can you provide a genuine mb part # for the front abs reluctor rings?

I messaged Konigstiger but haven’t heard back yet (he’s the man when it comes to parts)