Stop/start and EML on...?

[sidewaze samm]

I few weeks ago my engine management light lit up (amber). Car drove fine. EML goes off after a couple of hours.
This scenario has repeated since then, several times. Sometimes the EML is on for a few minutes, sometimes for a couple of days.
Booked in for investigation, but the EML went off before I arrived and I was told that the light needs to be on, as my 2014 car does not remember EML fault codes when the light is off.
But, it's impossible to get a booking at short notice and so far I've cancelled two further bookings because the light was off on each occasion.

Also, this past week the stop/start has failed to 'initialise' (I mean the ECO doesn't light up green showing that it will activate after coming to a stop) even when all obvious parameters for its activation have been met (outside temp, engine temp, current drain, time since last activated, length of drive...). Over some 10 days and 350 miles, the stop/start has probably been in 'initialised' state for about 25 minutes.

There are no issues with either the performance of the car or with it starting. Everything seems fine apart from the above.

Coincidence or connection? Anyone any solutions or suggestions?

 

[Slartibardfast1]

I few weeks ago my engine management light lit up (amber). Car drove fine. EML goes off after a couple of hours.
This scenario has repeated since then, several times. Sometimes the EML is on for a few minutes, sometimes for a couple of days.
Booked in for investigation, but the EML went off before I arrived and I was told that the light needs to be on, as my 2014 car does not remember EML fault codes when the light is off.
But, it's impossible to get a booking at short notice and so far I've cancelled two further bookings because the light was off on each occasion.

Also, this past week the stop/start has failed to 'initialise' (I mean the ECO doesn't light up green showing that it will activate after coming to a stop) even when all obvious parameters for its activation have been met (outside temp, engine temp, current drain, time since last activated, length of drive...). Over some 10 days and 350 miles, the stop/start has probably been in 'initialised' state for about 25 minutes.

There are no issues with either the performance of the car or with it starting. Everything seems fine apart from the above.

Coincidence or connection? Anyone any solutions or suggestions?

Maybe buy a code reader (icarsoft) and plug it in when the EML goes on again? Always handy to have one of these.

 

[Blobcat]

Fault codes should be stored as "historic" in the system - as per above get a decent MB specific code reader and take a look.

I'd also check battery voltage - >12.4V at rest with engine off is want you want

 

[ajlsl600]

Also stop start don't work if car looking for regen. Wot car is this?

 

[sidewaze samm]

Fault codes should be stored as "historic" in the system - as per above get a decent MB specific code reader and take a look.

That's what I assumed, but the dealer was quite certain that, due to the year of my car (2014), historic EML codes are not visible...

 

[00slk]

That's what I assumed, but the dealer was quite certain that, due to the year of my car (2014), historic EML codes are not visible...

Really, my Mercedes range from 2002 to 2014 and all show historical codes, now come to think of it, I have never seen an EML code....I have been wrong before

 

[sidewaze samm]

So an update...
After failing to work much, the stop/start seemed to give up completely. After a week or so of this the stop/start started to work again and the EML went off, but then when reversing off my drive, the engine just cut out - and the dash lit up like a christmas tree!

Restarted and all was fine - for a few minutes. At traffice lights, turned into a side road and power just evaporates, not sure I was even doing 10 mph and the dash display is saying DSR inoperative (now that's a button I've never pressed). No christmas tree lights this time though.
Pulled over, turned off and on - and everything is working fine again (apart from the Stop/Start light of course).

a few thoughts...
Does low battery voltage on these cars lead to wierd symptoms?
Could the auxilliary battery cause such issues? (and where is it, on a RHD car?)

 

[ajlsl600]

Test batts. Mb, s hate low voltage I had 2 pages of historic on my old benz all related to batt low
Aux does, I believe consumables and stop start.? Main just cranks motor. Car tryin to regen (where applicable) disables stop start.? If u read codes a half goosed batt will be fairly plain to see.

 

[sidewaze samm]

Test batts. Mb, s hate low voltage I had 2 pages of historic on my old benz all related to batt low
Aux does, I believe consumables and stop start.? Main just cranks motor. Car tryin to regen (where applicable) disables stop start.? If u read codes a half goosed batt will be fairly plain to see.

If the battery is duff, is it just a case of nip to Halfords and swap a new one in? Or is it different with this stop/start stuff?
I've heard about batteries needing to be coded to the car...

And does anyone know where the auxiliary battery is on a RHD GLA?
Presumably that should also be showing 12.4v or so?

 

[ajlsl600]

Not heard about coding batts but f all benz do wud surprise me these days!
Buy a varta or bosch u can close bonnet on that for a few yrs Google aux batt location my ml is rear right urs?

 

[Botus]

lets start at the important place

Stop start kills engine's. It does NOTHING but cause greater damage to the environment. It will be a better, safer, longer lasting car that will provide MUCH less pollution to the planet if this system is out of action and stays dead. It is an irritating gimmick with only one purpose - to destroy the engine to increase new car sales.

The control system to keep this functional has a number of needs, 1) main battery voltage high enough to restart a stopped engine, 2) no emission system requirement in play that needs to keep it running, 3) the small "motorcycle" control battery is in good enough condition to monitor the vehicles requirement and to control the premature death of your engine. Its is a normal service requirement to buy a new control battery every few years or it plays up. So buy a battery and then drive to a grown up independent dealership who can code out (software switch off) the dangerous feature forever.

Then let us know if its a tractor with a DPF as the other issues depend on the engine type

 

[sidewaze samm]

Have now borrowed a multi-tester and checked voltage of the main battery - 11.8V so a bit low, though plenty to start the car as normal, with no signs of difficulty at all.
The auxiliary battery will have to wait until at least tomorrow evening (I've only just found out where it hides).

And there's no DPF - it's a 250 petrol

 

[mercmancdi]

I m o 11.8 v is a bad battery regardless.

 

[Botus]

so I doubt the EML is driven by the stop start....

BUT you can get an intermittent issue that increases over a few weeks or even months (that randomly puts the EML on) caused by a nasty little sensor that frequently fails - fortunately they are cheap and easy to fix... if its not had one and in 6 to 10 years its done more than 50k miles, the CPS (crank position sensor) often goes strange and the car progressively stumbles to a halt at slow junctions, randomly throws the EML on and off a few times (but often not for long) and if you can keep going, often fails to restart when the engine is hot till its had a 1 hr tea break. Circa 50 quid and even if not today's issues will save a breakdown in not many miles time anyhow....

 

[sidewaze samm]

Update (and resolution?)...

Bought a new main battery (Varta, same as OEM but no MB branding) and fitted it today (bit of a pig to do).
On start-up, the now ever-present EML disappeared; went for a 20-mile drive, and throughout the drive start/stop worked as it should (though it will be switched off most of the time, but good to know it's working properly). Car drove fine.
So, fingers crossed that's all it needed.

Keep in mind that on earlier visits to the main stealers for this issue, I was told:
~ "On your car, we can only read diagnostic codes for the EML when the light is actually on"; and then on a further visit:
~ "Although the EML isn't on, we've managed to diagnose a wiring issue and although we are charging £110 for that nugget of information, you will need to book in for a full electrical investigation @ £150/hr, as we need to find out which end of the wiring (from the accelerator) the faulty wire/connector is. Wiring faults aren't covered by your extended warranty, and it's likely to take several hours and potentially run into a 4-figure bill".

I thought opting for a new battery at £170 delivered was worth a punt. I wonder what their price would have been?

Sadly, the same service dept at this stealership has also told me over the past three years that the cost of replacing the 'weathered' panel at the front of my pano roof would be prohibitive as it is part of the windscreen. However, their parts department managed to provide me with a schematic print, part number and cost for the section on its own.
Also, they have replaced the rear diff under warranty, but not before diagnosing that the noise I was reporting was caused by the fuel tank (!) and replacing that. And this in turn followed a diagnosis over a year earlier that the noise (the same noise, though more intermittent) was caused by my tyres and I should replace the whole set. From the very outset I had actively pointed them in the direction of prop shaft/diff/drive shafts!!

Chocolate teapot comes to mind...

so I doubt the EML is driven by the stop start....

BUT you can get an intermittent issue that increases over a few weeks or even months (that randomly puts the EML on) caused by a nasty little sensor that frequently fails - fortunately they are cheap and easy to fix... if its not had one and in 6 to 10 years its done more than 50k miles, the CPS (crank position sensor) often goes strange and the car progressively stumbles to a halt at slow junctions, randomly throws the EML on and off a few times (but often not for long) and if you can keep going, often fails to restart when the engine is hot till its had a 1 hr tea break. Circa 50 quid and even if not today's issues will save a breakdown in not many miles time anyhow....

Interesting - I'll keep it in mind should it be more than the battery, but I have a good feeling about this being OK. For now at least.

 

[EmilysDad]

Update (and resolution?)...

Bought a new main battery (Varta, same as OEM but no MB branding) and fitted it today (bit of a pig to do).
On start-up, the now ever-present EML disappeared; went for a 20-mile drive, and throughout the drive start/stop worked as it should (though it will be switched off most of the time, but good to nknow it's working properly). Car drove fine.
So, fingers crossed that's all it needed.

Keep in mind that on earlier visits to the main stealers for this issue, I was told:
~ "On your car, we can only read diagnostic codes for the EML when the light is actually on"; and then on a further visit:
~ "Although the EML isn't on, we've managed to diagnose a wiring issue and although we are charging £110 for that nugget of information, you will need to book in for a full electrical investigation @ £150/hr, as we need to find out which end of the wiring (from the accelerator) the faulty wire/connector is. Wiring faults aren't covered by your extended warranty, and it's likely to take several hours and potentially run into a 4-figure bill".

I thought opting for a new battery at £170 delivered was worth a punt. I wonder what their price would have been?

Sadly, the same service dept at this stealership has also told me over the past three years that the cost of replacing the 'weathered' panel at the front of my pano roof would be prohibitive as it is part of the windscreen. However, their parts department managed to provide me with a schematic print, part number and cost for the section on its own.
Also, they have replaced the rear diff under warranty, but not before diagnosing that the noise I was reporting was caused by the fuel tank (!) and replacing that. And this in turn followed a diagnosis over a year earlier that the noise (the same noise, though more intermittent) was caused by my tyres and I should replace the whole set. From the very outset I had actively pointed them in the direction of prop shaft/diff/drive shafts!!

Chocolate teapot comes to mind...


Interesting - I'll keep it in mind should it be more than the battery, but I have a good feeling about this being OK. For now at least.

.... and they describe cars having a Full Main Dealer Service History as a positive!