Recently purchased a 2016 E400 and in the few months I've owned it the start stop has never engaged. I chalked it up to the cold weather but now that it's warmer out I'm thinking something is wrong with the system.

The eco light in the center console is green and can be turned off if I press the button, but there is no ECO symbol on the LCD in the cluster. From what I understand the ECO icon should be there no matter what, and orange if it's inactive, and turns green when it will function. Is this correct? Is there a way to diagnose the system? There don't appear to be any warnings in the cluster and no lights on on the dash.

 

The yellow ECO light was on older models, My 2014 don't have it.
ECO stop needs to meet about 12 parameters to work. Weak battery (you have 2) is most common, but you need good scanner or good Gypsy with crystal ball to troubleshoot.

 

Have your dealer provide you a new accessory battery in the trunk. It is shot and I assume the car is still under the original warranty. You will be back to normal after that.

 

Another possibility is that vehicle was tuned and eco was disabled

 

Probably unlikely, the previous owner was an older single woman. But thanks for the heads up, didn't know this was possible.

 

Flat battery-99% of the time.

 

Thanks! It's going in for warranty tomorrow.

I'm surprised there's no warning to tell you that that's the reason for the malfunction.

 

-Nope. You will not receive a warning. When your ECO is not illuminated on the display is your only warning.

 

It could very well be the auxilliary battery. But also, according to the manual, there are a dozen or more parameters that have to be met before ECO Stop will work. In my experience, you have to drive at least 15-20 miles before the engine warms to ideal, tranny is at the right temp, you've passed two nuns riding bicycles, etc. Mine does not operate in the Winter, but I've driven only short distances since Nov.

 

A fresh battery will accelerate those parameters. Mine will kick in within the first mile of driving typically, whether winter, spring, summer, or fall. Just in time for me to remember I forgot to shut it off, because I can't stand it.

 

My 2014 was giving me aux battery warning and ECO still did work after some driving.
Again, we can crystal-ball it forever.
So to add to speculation, how about Martians riding in the trunk and draining electrical power?

 

Sounds like a blessing to me. If I had a year with that feature I'd find someone with a STAR computer to code it out.

 

Under the microscope: ECO start/stop: Sophisticated technology gives the highest levels of efficiency
agreed... not my favorite "feature"... especially not being able to deactivate and keep it deactivated - having to turn it off each time you start the car is a PITA.

 

There are easy (although not cheap) chips that will disable ECO, but I am one of those few who actually like it.
I live 5 miles from freeway with big intersections holding me for 2 minutes on red light.
I got used to car quieting down with ECO stops, that now I am annoyed when it is still idling. Not to mention observing mpg going from 35, to 30, to 25 while not moving an inch.

 

Dealership confirmed it was the battery. Thanks everyone.

 

Now you can decide whether to use it or not. Lol

 

how much they charged u for a battery?

 

just pull the stop start fuse in the fuse block. Fuse #91 on my A207. Easy....

 

Covered under warranty.

 

I have a 2012 and am glad I don’t have thus feature

 

Right you are, and thanks. My ECOstop button light was green, but it took several miles of driving before it would function. Per your comment, I visited the dealer, and indeed, the main battery was dead or not working properly.

They replaced the main battery under warranty, and on the way home, I had to turn ECO off to keep it from working at every stop light. Thanks for the advise.

 

^ Ha that's awesome!

 

My ECO had been lazy for a mighty long time ever since the car was new. Back then I did not know about Bosch lazy charging.

Recently I ran a bus scan and cleared all faults then ECO worked normally again!
Now the ECO symbol goes from yellow to green promptly after warm up and no longer blinks ON/OFF then ON. Stays ON solid.

The Main battery active charging now stays up longer above 14V before going into variable charge mode (12.6 to 14.9).
What is interesting is when MAIN+AUX batteries are normally charged, ECO works just fine...
So when the ECO functionality is acting up it is really caused by the crappy MAIN battery management issue, not so much the AUX Batt.

I am/was guessing here that Rear-SAM impacts the AUX-Batt management & ECO interface. The "ECO" function runs on the main Fuel-Injection computer - (I later confirmed my assumptions by digging deeper specifically into MY14 W212 E35 schematics)

Rear-SAM seemingly unrelated faults are the proverbial "tip of the Iceberg" of R-SAM gone wild:
- B164B00 Right Rear TURN Signal has malfunction
- B164A00 Left Rear TURN Signal has malfunction
- B280315 Right Stop and TailLamp has malfunction (Short to positive or OpenCircuit)
- B280115 Left Stop and TailLamp has malfunction (Short to positive or OpenCircuit)
These faults are stored but all tail-lights work fine regardless... It's just the R-SAM acting up (Mfg by HELLA 2011)

By any chance, anyone have you seen these sort of recurrant RearSAM faults or glitches or RFK-Camera on your E-Class, which one mainly??
Can't find MY14 TSB or campaign to make sense of these Rear area faults, trunk GND distribution Ohms out Ok

 

Simply swapping batteries under warranty does NOTHING to fix the underlying cause of low-charge, low-voltage! So I took a couple of hours to research the "Charging" diagram - I quickly realized that W212 cars with "FRONT MAIN BATT" are still basically using the "REAR MAIN BATT" design.

Legacy spaghetti:
- The MAIN battery negative-post sensor data (Amps&Volts) travels from the FRONT all the wayto the REAR-SAM on the LIN bus.
- REAR AUX-ECO battery relay is controlled by the FRONT Driver-SAM
So now the wiringis crossed compared to when the MAIN-Batt was in the rear and AUX upfront, not necessarily bad though.

Charging based on Rear-SAM sensor:
The above finding links how a crazy Rear-SAM loaded with transient false errors can affect the charging voltage... . It is the Rear-SAM job to to translate the MAIN-Batt LIN-Bus sensor onto the "CAN-C". From there the main ME-SFI computer software can manage the Alternator.

Rear-SAM... a catch-22!
low-voltage spikes disrupt R-SAM and cause the charge voltage to then deep even lower below 12.0v

Scenario:
- You float your main battery or drive a lot without any ECO stops.. reaching unintended high-level of charge (**)
- Charge algorithm decides to drain down MAIN Batt below 11.x Volts under the engine bay
- Rear-SAM supplies many heavy loads far away from Alternator with many junctions sees significant line voltage drops
- Rear-SAM processing chokes up on low-voltage glitches (CPU power runs on regulated & filtered 3.3 or 5VDC)
- ? Alternator control software goes nuts and commands a low-voltage safe-mode to prevent over-charging BATT hazard ?

Note: I could not find the "battery temperature sensor"... (See Edit: N2: found it!)
Anyone knows anything about it ??
It's bound to affect charge vs. temperature

(**) Battery floaters beware:
it seems to me the software interprets an extremely quick charging battery (that was charged externally to 100%) as a nearly dead low capacity battery... then goes into conservative low-voltage - Essentially by trying to keep your battery well charged you end up with low-voltage and multiple Faults.
My workaround for now is to exercise the battery calibration with ECO cycles to request further charge from system.
Restarting the car (Key OFF>ON) always initiates a fresh charge cycle...

-> Please read my research notes mixed with your own knowledge and a grain of salt... hope this helps dismiss battery chaos

-------------------------------------------------
EDIT 2: Hyundai "Battery Sensor": Amp/Volt + Temp !

I did locate the "Battery Temperature Sensor": it is hosted by the HYUNDAI sensor on battery (-) along with the Volt/Amp shunt. If you can get a dynamic reading on "Workshop Menu" then the Hyundai module is communicating correctly (LIN bus to Rear-SAM then back to the engine bay computer).

- Evidences are pointing at the charging software having issue with the battery charge percentage or trying to figure it out by actively draining while driving. All the charging hardware does test A-okay (battery, alternator, cable connections, BattSensor, RearSAM...: no prob!)

- I would not be surprised by Hyundai integration issues with the battery management system...?

- CALIBRATION: It seems productive to manually perform a partial battery discharge so the computer can learn or update precisely what the battery is up to: "State of Charge", "Lifespan" etc... these battery parameters are tracked directly inside a Bosch battery sensor but here MB is using a Hyundai copy cat.

-------------------------------------------------
EDIT 3: CAN-B testing with a scope
While working out which module on the busy CAN-B is impacting the charging system ... I managed to get a nice consistent BATT charge then got ECO display Green_Flag in no time.
So ECO woes on low mileage cars are ONLY the tip of the iceberg for low voltage battery management that is also the cause of numerous "Beep-Beep Inoperative etc" message.

Under testing:
- This chain of chaos seems caused by CAN disruption
- 5 independent CAN buses so when one is screwed up, the others 4 buses are unaltered
- As usual: check the obvious 1st... hardfault modules
- [Youtube "DiagnoseDan" is a master !]

 

That's about all I could understand from the reply, but good to know.
Thanks