Engine fails to auto stop.

[bob12]

After searching through the threads and trying to find something about the system that stops the engine when I take it out of gear I am assuming my problem might be software related and need a machine connected to correct?
About 95% of the time the auto stop just fails to work, 4% of the time it stops and then starts up again as if to say "I know how to stop I just don't want to".
Leaving 1%. I think once in the last 6 months the engine has stopped properly, all that trip it worked fine but the next time I used the car it ignored the opportunity to stop.
Is this a software fault do you think or is there a sensor somewhere that needs replacing?
I have heard other people complain about their car always stopping, would one like to swap the faulty unit with me?
Thanks
Bob.

[RiveriaMan]

Hi Bob
You don’t show how old your vehicle and hence your battery is, but even if new then there is still all sorts of other criteria that needs to be met by the car system before it will allow the stop/start to kick in. So if things like the battery is old and has a low capacity at the start of the journey, or that there is alot of drain on the system already prior to any stop I.e you have had the AC running full power for a prolonged time or headlights on etc then stop/start will not auto kick in, there is more likely others like lots of short runs and no real long runs of the vehicle but certainly it is not a given every time you stop at traffic lights or in traffic that the engine will stop also. Below is the full list of situations in which the stop/start will not activate from the manual.

[gloucester]

Welcome to this forum - you're lucky it's stopping 5% of the time.

On my car I used to call it the "out of county" start/stop since it would only usually activate after a drive of at least thirty miles.

Once I drove approx 100 miles to Heathrow - it worked when I paused in a layby. Then 100 miles back - and it wasn't working the next day!

A new battery didn't make any difference - the garage said I wasn't driving aggressively enough!

I believe there is an inborn problem on the J11 at least with the charging system not charging the battery sufficiently.

Conversely my present car is a dream - working 95% of the time.