W212 Eco Start/Stop Not Functioning

[Brizzle]

A few months ago I purchased a 2016 E220 Bluetec estate and am thrilled with it. I spent some time finding a car without too many toys/bells and whistles as I prefer to be in control of what happens when I'm driving. One thing I did want was the Eco start/stop function to assist with fuel consumption. Initially this was working fine but a couple of weeks after taking delivery I got a dash lit up red with a battery charge warning and sure enough the battery voltage (as read by my OBD reader) had dropped. Switching the engine off and back on again seemed to have cured the problem as voltage was back up around the 14.5V region. However, the start/stop had stopped working and there was now a fault recorded which suggested that the MAF sensor was faulty.

I fitted a new MAF, sourced from my local main dealer, and cleared the fault (which hasn't reappeared) but the start/stop still isn't working. The OBD reader isn't showing any faults at all. Any suggestions as to what else I can check?

 

[sl500amgsport]

A few months ago I purchased a 2016 E220 Bluetec estate and am thrilled with it. I spent some time finding a car without too many toys/bells and whistles as I prefer to be in control of what happens when I'm driving. One thing I did want was the Eco start/stop function to assist with fuel consumption. Initially this was working fine but a couple of weeks after taking delivery I got a dash lit up red with a battery charge warning and sure enough the battery voltage (as read by my OBD reader) had dropped. Switching the engine off and back on again seemed to have cured the problem as voltage was back up around the 14.5V region. However, the start/stop had stopped working and there was now a fault recorded which suggested that the MAF sensor was faulty.

I fitted a new MAF, sourced from my local main dealer, and cleared the fault (which hasn't reappeared) but the start/stop still isn't working. The OBD reader isn't showing any faults at all. Any suggestions as to what else I can check?

Almost definitely going to be battery related, Mercedes are renowned for giving false warnings/readings once the battery condition becomes low. Check if/when it was last replaced, they tend to have a 5-7 year life and you may still be on the original battery. If so replace it and I bet it fixes all the issues (may save you a lot of unnecessary repairs).

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[Brizzle]

Almost definitely going to be battery related, Mercedes are renowned for giving false warnings/readings once the battery condition becomes low. Check if/when it was last replaced, they tend to have a 5-7 year life and you may still be on the original battery. If so replace it and I bet it fixes all the issues (may save you a lot of unnecessary repairs).

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Many thanks for your response. This supports what was suggested last week at a track day. The battery is the original so I guess it's time to spend a small fortune on a new one. Do I need to change both batteries or just the starter one?

 

[AMGeed]

^ Check the voltage on the auxillary battery. It should read at least 12.4v standing.
If its original, I'd be tempted to replace anyway. At 8 years old its had a good run.

This Varta aux' battery is very similar to the MB Fiamm branded battery at half the cost.

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[sl500amgsport]

Sounds like Aux but if both are original if it were mine I would replace both, don't have to buy Merc originals (they tend to be Bosch) as long as they match output and physically fit...

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[malcolm E53 AMG]

Certainly worth investing in a multimeter so you can check the voltage of both batteries anything <12.4V can lead to ancillaries shutting down including the Stop/Start system - totally agree with the above MB cars don’t take kindly to under-voltage batteries especially when running COMAND and AC

 

[sonic]

My 212 of 2011 vintage is still on its original battery. I only do about 4K miles a year in it, but it goes on the charger/conditioner every month.

 

[star]

I'd leave it not working, it seems timing chains wear far more with stop/start working, then those which is either switched off or not working.

 

[Wighty]

Just a thought , but if a diesel is doing a regen does the stop start system interrupt that process ?

 

[sl500amgsport]

Just a thought , but if a diesel is doing a regen does the stop start system interrupt that process ?

I believe it would the same way as a regeneration often gets interrupted when you suddenly hit traffic slowing the car below regeneration conditions.

In my last diesel (Jag) it was a bit like range anxiety, would take it for an Italian tune up when the warning light came on and swear if I hit traffic after it started!

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[dry run]

I'm sure my car is capable of completing a regen on tickover. Sometimes if I've come to the end of a journey and my car suddenly decides to start a regen (holds gear changes to 2,500 rpm, white smoke out the back, exhaust gases very hot, etc.), I simply leave it in my parking space on tickover for a while and it seems to complete it and drives normally again when next started.

 

[sl500amgsport]

I'm sure my car is capable of completing a regen on tickover. Sometimes if I've come to the end of a journey and my car suddenly decides to start a regen (holds gear changes to 2,500 rpm, white smoke out the back, exhaust gases very hot, etc.), I simply leave it in my parking space on tickover for a while and it seems to complete it and drives normally again when next started.

I bet it doesn't complete with the engine switched off on stop/start unless Voodoo is involved ;-).

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[Monday]

The only time I had stop/start fail (in a 2015 E350 Blutec) there was a separate (small) stop/start battery under the passenger side dashboard. It was replaced under warranty so I know no more about it. But it was separate from the starting (under the bonnet) and auxiliary (in the boot) batteries.

Maybe it's changed but star maybe right, you are better off without stop/start.

 

[EmilysDad]

in just over 40k miles & just over 5 years I've yet to be aware of my ML doing a regen ....

 

[sl500amgsport]

in just over 40k miles & just over 5 years I've yet to be aware of my ML doing a regen ....

Is it diesel

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[dry run]

I bet it doesn't complete with the engine switched off on stop/start unless Voodoo is involved ;-).

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I bet it doesn't complete with the engine switched off on stop/start unless Voodoo is involved ;-).

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I always disengage stop/start - part of my start-up procedure

 

[Brizzle]

Hi folks, sorry I haven't responded to any of the above posts - life's been a bit hectic

I will be replacing both batteries this weekend - they're both originals - with "compatible" models and will see where that gets me. I'll keep the old ones topped up as spares just in case. I was rather shocked at the premium you have to pay for a start/stop battery (and air filter too).

As far as regenerations goes, a friend of mine has a computer/software that can force a regen - don't remember what it's called - and we did that last weekend even though the data from the various sensors in the exhaust system looked normal.

I'll update once the batteries have been replaced

 

[AMGeed]

If you have OEM batteries and have a Mercedes commercial dealer nearby, make a note of the Part numbers on the batteries and get a quote from them.
Often a saving using the van spares instead of the car spares dept.

 

[Brizzle]

If you have OEM batteries and have a Mercedes commercial dealer nearby, make a note of the Part numbers on the batteries and get a quote from them.
Often a saving using the van spares instead of the car spares dept.

Thank you. That sounds like a good idea