Just noticed that my 2014 L494 has this (when I say noticed I mean noticed the button near the gearstick)

Only thing is it's never actually stopped the engine when I brake to a halt

Is there a menu where this may have been disabled?

Or is there more likely a fault which is stopping it from working (low battery charge for example)?

Hi James,

aux battery powers stop start..so if low ..stop/start wont work.

Also if DPF is in regen mode then stop start wont work and if fuel level is below a certain amount, it wont work. Can't remember the fuel level though.

The engine will also restart if one of the following occurs:

Here is a list of conditions

Intelligent stop/start is deactivated.

An automatic transmission shift paddle is used to select a gear.

Demand from the Climate control system increases.

The vehicle's battery charge becomes low.

Brake vacuum has been reduced, for example, using the brake pedal repeatedly with the engine off.

The accelerator pedal is pressed (non-Hybrid vehicles only).

Reverse (R) gear is selected (non-Hybrid vehicles only).

The vehicle's speed exceeds approximately 1 km/h (0.5 mph) (non-Hybrid vehicles only).

The following conditions will prevent an automatic engine stop:

An automatic transmission shift paddle has been used to select a gear.

The external temperature is less than approximately 0°C.

The external temperature is more than approximately 40°C.

The engine has not reached its operating temperature.

The driver's seat belt is not fastened.

Demand from the Climate control system requires the engine to be running, for example, when in Defrost mode.

The vehicle's battery charge is low.

Intelligent stop/start is deactivated.

The bonnet is opened.

What the last post says, but will almost definitely be battery related

I've edited this post as it was TLDR and only offering some solutions on how to solve the issue. (it was a slow day for me Server updates!) Hence the comments that follow this!

JimBG has explained how the ASS operates further down this post

Good luck chap If a jobs worth doing, get a someone who knows what they are doing to do it!

RRS Autobiography Indus
RR P38 HSE V8
RRS Supercharged Santorini
AMG CLK Rear Tyre Shredder

Last edited by pjbracer1 on Thu Feb 18 2021 9:38am. Edited 1 time in total

I take it you had a slack work day pjbracer  MY18 SCV8 Satin flux silver
Gone:
MY19 SV VELAR AUTOBIOGRAPHY firenze red
MY18 SCV8 Yulong white- perfect 👍
MY16 SDV8 SANTORINI BLACK - perfect 👌
MY64 SCV8 DARK BLUE - nightmare car
MY64 SCV8 FIRENZE RED - loads of annoying issues
MY15 SDV6 FIRENZE RED - perfect 👌
MY12 SDV6 DISCO4 IPANEMA SAND - perfect 👌
MY09 TDV6 SPORT BLUE - lots of issues

That is a very long and detailed response.

I just copied and pasted

Canary wrote:

I take it you had a slack work day pjbracer

Ha yeah I definitely did thats what IT does to me!  If a jobs worth doing, get a someone who knows what they are doing to do it!

RRS Autobiography Indus
RR P38 HSE V8
RRS Supercharged Santorini
AMG CLK Rear Tyre Shredder

Very long replies!

It helps to understand the basics of why there is an aux battery in the first place, and it is NOT directly for Stop/Start as such.

With the introduction of Stop?start it became necessary to protect all the various electronics in the car.
The electronic are very susceptible to power fluctuations such as when there is a heavy load, i.e. starting.

So the electronics needed the aux battery to avoid that dip.

So if EITHER battery is low the start/stop is disabled to maintain that stable supply for the electronics. 2023 P440e SE Dynamic on order -cancelled

2022 HSE Dynamic P400e

2017 Discovery 3.0 HSE Silicon Silver Nimbus interior and a few extra toys SOLD

2013 HSE Black, Orkney Grey, Ebony Seats and Ivory Interior SOLD

2006 HSE

Plus a few other cars inbetween!

My stop start stopped working 2 week after getting the car. Once I started putting car on ctek charger it started working again. Only works for a week or so due to the mileage I do.

Ditto per JOhnRRS - once CTEK conditioned (via terminal in the engine bay), bloody stoop start working all the time... MY16, 3.0D HSE Dynamic, Barola Black, TV, Rear Entertainment, Opening Pan Roof, Meridian

you do know that you can switch off the stop/start?

Whats the cheapest I can get one of these ctek conditioners for? Debating whether to shell out on one of them or just buy a new battery

I think mine was £80

Just got one on Amazon for £69 couldnt find one cheaper and the ones that were had shipping so no brainer really.

Tried in on my old battery on recon mode so will keep it topped up as a reserve If a jobs worth doing, get a someone who knows what they are doing to do it!

RRS Autobiography Indus
RR P38 HSE V8
RRS Supercharged Santorini
AMG CLK Rear Tyre Shredder

Lidl £15 conditioners get a good press. I have Ctek MXS 5, also Ctek Stop/Start model & a Lidl effort. All good but if pressed I would go for MXS 5 as the booklet explains more what the lights do than the others, but saying that, £15 as opposed to £60 +
no brainer. My chargers can be on for 6 months at a time. Cars always start first time & stop/start works fine

RRS MY17 and on have no auxiliary battery.
Is there a way to cancel the engine stop-start function as not to have to push on that button every time you get on board of the car ?
Thanks Nik
RRSport L494 SD4 MY'17
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