Often while driving my 2007 S550 I'll get a warning that ESP and ABS are inoperative, then Park Assist inoperative, then Distronic inoperative. Everything else operates as normal. Sometimes it all comes back on, sometimes after the car has cooled off everything returns to normal.
NO CODES
I've load checked the batteries and have passed with flying colors. I did notice the front battery was a bit slow to come up to charging voltage (engine running).
I suspect a weak voltage regulator or alternator, what say the forum?

more likely an ABS sensor playing up - check all four wheel speeds in live data - wire breaks make the left rear play up

cruise often cuts out if the ESP isn't available - the ESP and the Park brake rely on the ABS readings

low volts aren't great - and regulators can be changed - but as all are related and the car has a penchant to store codes for low volts I'd start on sensors

Would a bad wheel sensor not set a code?

sometimes...

Latest problems, I lose most of the power steering and get a warning "EMERGENCY BRAKE See owners manual"
All of the above occur after I drive 60 +/- miles. Up until then everything works perfectly.

Duplicate

because modern cars have canbus comms with many modules lots of fun can ensue

electronic release of the park brake uses the ABS sensors....
the gearbox gets info for the traction control from the ABS wheel speed sensors
the PAS uses vehicle speed to alter the assistance level as the speed changes so this can go full heavy or fully light whenever it fancies
the ISM connects to the electroplate in the gearbox to get between P N R and D so it can even lose its gear selection
gear selection can get muddled and change 5th to 2nd etc.
no doubt the suspension has a temper tantrum too

all are standard bits of fun to expect on any drive at any time - you have to love german engineering and designed to fail electonics

Classic voltage issue. Even if batteries test fine, a weak alternator or failing voltage regulator can cause intermittent ESP/ABS/Distronic faults. Check alternator output under load should be 13.8-14.4V. If it’s dipping, replace the regulator or alternator. Worth ruling out before chasing ghosts.

That’s what I was thinking, the car stays in a battery maintainer and probably has enough charge to last an hour or so before the “modules” start acting up . Carfax indicated the P. O. had a rebuilt alternator installed some time ago.

You can insert a cheap voltage reader in the cig lighter and monitor system voltage in real time while driving.
I purchased one with USB outlets so I can also charge phones. It now lives full time in the lighter.

read my mind! Bought a pair of cheapie voltmeters from the jungle site and so far the system hasn’t malfunctioned yet. Running I get 14.3V at the front battery and 13.6V at the trunk battery. More later.

It is charging. Time to plug into XENTRY and monitor individual wheel speeds while driving.

Hello,

In my case, which was exactly the same as yours the following happened:
* Replaced ABS sensor, error came back either instantly or after 5-15 minutes
* Replaced wiring with new pins from ABS computer <-..> ABS sensor, no change
* Replaced entire wheel hub from another car, to eliminate *any* chance this was about the ring/bearing

None of this worked

We then took the ABS computer to a shop that does ABS/ECU rebuilds, and they re-flowed the CPU on the ABS computer. Problem is now solved, car has traveled 500KM without issue.

I have ordered a new ABS computer from Mercedes and I will have it in 3-4 months, part is on back order.

Reasoning for order of computer:

* I cannot be thinking about this, I have enough on my mind
* I have lost trust in the ABS computer at this point
* If it needed a re flow, it means it's game over
* Yes, the rebuild will likely hold forever, but I'm not taking that risk

Why?

* Imagine a scenario where you have music on, sunroof open, summer, heavy light coming, instrument cluster not immediately 'active' visible due to sunlight hitting you hard
* You're driving well, pushing the car, expecting it to work as you know it can
* All of a sudden you need ESP, i.e. your driving depends on it - and it's not there, boom, you're either injured, paying, or 6 feet under

I can't take that risk.

If I was the type of driver that would be at speed limit w/o music, 100% focused, I could keep it as -is.

If you're still suffering please check the ABS computer.

ABS modules dying is 100% normal on ALL brands - ABS modules failing on Mercedes quite unusual

all my BMWs have had them replaced or repaired - last about 5 minutes - its ALL done on purpose - the industry are just criminals

https://www.ecutesting.com/product-c...dule-combined/

Just a follow up, decided to replace four wheel speed sensors.... And with guarded optimism NO MORE WARNINGS!

Thanks to everyone that responded.

A better solution is the AMG menu and there will be live charging on the clocks without buying unnecessary gadgets for the cigarette lighter.