Auto start/stop

[Ian Marsden]

2017 Diesel auto S-Max

Auto start/stop not working.

I charged up the battery to full as I know that can be a cause. The battery fully holds a charge and is in good order. Went in to my Ford dealer who tried to say the vehicle was fitted with the wrong battery (I’ve had it from new, never changed the battery) Then they decided in fact the battery just needed a charge (even though I said I’d just done it and it didn’t make a difference) I was then told it can take up to a month for the system to start working again??

What are the common reasons for this system not working and can it ever be fixed once it stops. I’m not convinced my local Ford has much of a clue on this one???

Thanks

[Paulius55]

The main reason is the battery state of charge (SOC) as perceived by the battery Monitoring System (BMS). This refuses to let the stop/start, or the heated front screen, operate if it assesses the SOC to be too low. Even if you charge the battery up it may still assess the SOC to be too low. The battery type should be an Enhanced Flooded Battery (EFB), designed for stop/start vehicles. You could check if your battery is of that type. The thing you can do is to reset the BMS, either by Forscan or with a combination of switches. I have a 2018 version diesel auto and I can reset the BMS as follows. Press the power button, but do not start the engine, flash the headlights 5 times then press the brakes 3 times. If it works the red battery warning lamp on the dashboard will flash after a while. You may well find that the stop/start will work again, but after a while it may cease to work again. A very long run at motorway speeds often brings the SOC up sufficiently to enable the stop/start by itself. Good luck.

[anon]

My dealer charged £52.50 to charge the battery. Fuel for 200 miles would cost about £25. Plan on a long run (yes, 100 miles out and 100 back), use the cruise control as much as possible and then leave it locked overnight.  It will be working in the morning.

[unofix]

On 5/17/2021 at 9:04 AM, unofix said:

The Start/Stop technology is the greatest thing ever to be fitted to any Ford vehicle. It provides thousands of posts on this forum of those who feel it saves the planet, and those who feel the inventer should be given a slap and told not to be so stupid.

Of course your Start/Stop system doesn't work, you have more chance of winning the lottery. There is a list of about 20 things that have to be "Just right" before it will operate. The most common reason for it not operating is the battery charge is too low. Other things are the battery is too hot, the battery is too cold, the heated seats are on, the heated windows are on. You will never fix it as actually its not broke. One day when you least expect it and probably at the worst possible moment it will turn your engine off just to prove it can.

If you do a search of these forums you will find so many threads on the subject it will give you enough reading for a week.

 

[anon]

It will only turn it off when you are stationary and will restart as soon as you put your foot on the clutch. Too hot and too cold? Nonsense. I have had the system work on very hot days where the engine was slow to start due to the fuel temperature, as well as within a mile on a -4 morning, lights on and heated windscreen having been on to clear the screen before departure. It really is not that fussy. It wants a little engine temperature and a well charged battery, that's all.

Those who consider it to be unreliable witchcraft have not taken the trouble to find out how it works from authoritative sources and then understand what is being explained, hence the semi paranoid ranting from those who don't like the system, fearing it will kill their batteries, starter motors or children. It won't do any of these but it requires the car to be used for more than a daily two miles to the station.

[iantt]

New battery will fix it. 4 years out of a efb battery is about it for stop start. 

[Bo Jensen]

On 5/20/2021 at 9:00 PM, Paulius55 said:

The main reason is the battery state of charge (SOC) as perceived by the Battery Monitoring System (BMS). This refuses to let the stop/start, or the heated front screen, operate if it assesses the SOC to be too low. Even if you charge the battery up it may still assess the SOC to be too low. The battery type should be an Enhanced Flooded Battery (EFB), designed for stop/start vehicles. You could check if your battery is of that type. The thing you can do is to reset the BMS, either by Forscan or with a combination of switches. I have a 2018 version diesel auto and I can reset the BMS as follows. Press the power button, but do not start the engine, flash the headlights 5 times then press the brakes 3 times. If it works the red battery warning lamp on the dashboard will flash after a while. You may well find that the stop/start will work again, but after a while it may cease to work again. A very long run at motorway speeds often brings the SOC up sufficiently to enable the stop/start by itself. Good luck.

I changed the battery and followed the description, now the start/stop function works in my S.-MAX from 2016 again

Thanks.

[unofix]

5 hours ago, Bo Jensen said:

I changed the battery and followed the description, now the start/stop function works in my S.-MAX from 2016 again

Please be sure to call back in a few months time to let us all know how it is still working !!

[Paulius55]

7 hours ago, unofix said:

Please be sure to call back in a few months time to let us all know how it is still working !!

Or just change the SOC to 90 or 95% and it will all work when you need it.

[unofix]

3 hours ago, Paulius55 said:

Or just change the SOC to 90 or 95% and it will all work when you need it.

Shsssssss That information is classified "Top Secret" we don't want everyone knowing that 😉

[Paulius55]

It's amazing, (or is it?) how many times this subject crops up on the various Ford forums. I wonder if the ability to search or research has evolved out of most humans....