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I’ve been trying to figure out why my ECO stop on my 2016 E350 isn’t working. The button always glows green but it’s only worked once. I was told to check the Battery voltage. When idling under full load it’s this
UB 14.8 V
IB 12- 30 A (it changes continually)
When sitting before start up it’s
UB 12.1 V
IB -11.6 A
after start up it immediately jumps back up to 14.8
and 12.1
What does that tell me?
Last edited by DeutscheBenz726; May 5, 2021 at 01:47 PM.
What you're observing is the main battery getting charged.
There is a laundry list of conditions that all need to be satified for the ECU to allow ECO:
- Driver seat belt
- Gear in D
- Engine temperature
- Main battery charge condition
- AUX Batt charged
- perhaps a few more...
Have you tried to simply charge your batteries? How does that improve ECO during the very next driving cycle?
I am sure you'll get your ECO working normally.
-----Edit!!!
I forgot the CABIN TEMP needs to be satisfied (turn OFF HVAC for testing purposes)
The "battery charging" and the "battery being charged up" (full) are two different things....
Last edited by CaliBenzDriver; May 6, 2021 at 05:31 PM.
Reason: OMG!
The last time I put my battery charger on my main battery, the eco start/stop was working perfectly. I just put it on the charger for about 3 hours two days ago, got it to 14.3 volts which is the highest the charger goes to for the main battery. Still hasn't activated ironically (even with oil, coolant, and trans temp up to temperature). A/C was not running as well, as with A/C on I've never noticed eco start stop work.
Some scanners will give you test page with all involved parameters on it, so you can troubleshoot.
Per my experience, main battery voltage is most common issue. Even battery test good, the system checks it very carefully. I had ECO restarts, when I was still stopped. Scared de heck of me 1st time.
Since I don't drive the car every day, I hook it up on battery maintainer. Then the ECO engage right away. If not- takes several miles of driving before stops will happen.
Yesterday when I ran the through the voltage on the car it looked normal but this morning I thought, what the hell. I’ll hook the trickle charger up to the car and I got the pic below. I bought the car second hand a month ago so I don’t really know how old the battery is. I guess a new battery is in my future!
Well it charged up enough for the green light to come on (after three hours). I disconnected the charger and turned off everything in the car and took it for a ride (no eco stop though). When I got home I hooked it back up to the charger and the charger immediately turned red so I’m guessing that it’s the battery.
Testing the battery can be pretty tricky as you are judging chemistry by measuring electricity.
I have 2 testers, when Solar tester will read CA and load tester will read voltage drop.
If you don't have tester, easy way to check battery status is to scroll the cluster to voltage display with engine off and then turn all the headlights and blower on high.
Voltage drop will give you good indication about battery condition.
Than you can turn the engine on and see how alternator performs
Yesterday when I ran the through the voltage on the car it looked normal but this morning I thought, what the hell. I’ll hook the trickle charger up to the car and I got the pic below....
I guess a new battery is in my future!
Promise yourself to do the same simple "charger test" on the new battery after a week.
Promise yourself to do the same simple "charger test" on the new battery after a week.
A new battery is always a good thing for safety.
What safety?
Getting new battery those days is not as simple as it used to be.
Too often new battery will day after 2 years, when older batteries can last for 10.
Well I took the car to autozone (yeah I know, you can beat me with a brick later) and had them test the batteries. The person that did it had worked in the parts department of an MB dealer in a town about an hour away and said she knew what she was doing. She tested the front and it was a little low but she said it probably should be replaced because it’s the original battery and is at least 6 years old. Then she tested the battery in the back and said it was “as flat as a pancake”. When I asked about replacements she told me that they’re not allowed to replace them and recommended that I take it to the Mercedes-Benz dealer.
does that sound reasonable?
Last edited by DeutscheBenz726; May 6, 2021 at 05:39 PM.
I would connect your charger to rear AUX battery overnight. It being flat failed ECO checklist. Charge then evaluate its condition for it perhaps surving prolonged discharge...
Replacing that small $100 AGM is a 10mn job if you are up for it.
Last edited by CaliBenzDriver; May 6, 2021 at 05:56 PM.
Lots of threads here on battery replacement. You can do both if you need to with no issue. The dealer is not necessary and they will ruin your day with the bill.
I wouldn't rely on the charger "test" and regarding Autozone, my guess would be they don't carry that particular style... hence why they didn't offer a sale. The auxiliary battery is not a "common" battery.
Put a DMM to the aux battery and report the voltage... if its too low, as the Autozone test would suggest, then it might be perished and no amount of charging will help. It won't hurt to try connecting the CTEK... but it has logic if the voltage is too low, it also won't charge the battery.
The thing that got me was that she didn’t try to sell me a battery but instead referred me to the Mercedes-Benz dealer.
Originally Posted by bmwpowere36m3
my guess would be they don't carry that particular style... hence why they didn't offer a sale.
I agree. There is nothing special about getting the battery from the dealer, other than the high price. If batteries are original, it may be time to change them out anyway.
Still make sure the key is out of ignition and dealing with potentially discharged battery, I would pull the clamp from it before putting charger on it.
It doesn't happen very often, but just last January my Sprinter HP fuel pump broke and dealer's mechanic was trying to troubleshoot it on weak battery, frying ignition module as the result. That made $1000 flying out the window very fast.
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