2016 XF start stop doesn’t stop engine

[Linkpin]

Engine doesn’t turn off at stoplights or stop signs, should I worry engine will quit later on?

 

[Big John]

Hi Frank and welcome.

The stop/start system will only stop the engine when the car is sure that there will be enough "left" in the battery to restart it. So it will not stop if you have the Air-con on full blast for example, or if battery is voltage is low or the engine is cold etc. Usual cause of s/s not working is low battery level. It is very common at the moment with the lockdowns we are all enduring. If it has been sat and just done short trips to the shops it could just need a good run. Personally I am a big fan of the Ctek trickle chargers to keep the battery topped off. It is also worth getting a simple cigarette lighter socket voltmeter to keep an eye on the voltage. Certainly in the x250s the battery is an AGM which has a different voltage profile to an ordinary wet cell but is capable of withstanding deep discharges. 12.8v at rest is pretty full 12.2v at rest is pretty low. It is worth noting that battery voltage may well show below 12v when starting but that is with all of the computers running rather than at rest. A quirk of these cars is the battery management is a bit too clever for its own good (IMHO). every six months it will actively discharge the battery to 75% and the voltage when running will be held around 12.2v. It does this so that it can work out how able it will be to restart the car. In my opinion that is fine unless..... it gets to 75% just before you park up in a pandemic and doesn't get a chance to recharge. Hence my advocacy of the Ctek chargers 🙂

Of course at 5 years old you may be due a new battery anyway 🙂

Kind regards

John

[David Taylor]

I had the same issue with a previous XE-R, as well as my current XF-R. Will have to give @Big John's advice a try, but pretty sure I didn't have aircon on. Also had the issue pre-pandemic, even when driven every day. Will get a trickle charger, see if that helps. Cheers John. 

If not the battery, any other suggestions?

[Tomato]

Lots of issues due to lockdown. Cars need to be run for a bit before stop/start will work again if battery drained from standing still. I has a 2 hour round trip before it started to work again, although I do usually turn it off anyway 🙂

[Big John]

Also....Don't forget that both batteries need to be OK as the little one is there to ensure the voltage to the computers does not get problematically low during the stop or on restart and the computers are very hungry on power. 🙂

[alspal]

Can only echo the comments about the fact that it’s most likely the battery being the reason why the stop start is not working. My 2016’s stop start didn’t work for months until I had to do an essential work-related 100 mile round trip journey and hey presto it started to work again.  Also the 2016 X260 models do not have a secondary stop start battery as is found in the X250 models.  The X260 XFs only have one battery.

 

 

[Ian Manning]

My strong advice would be to start with the small battery. When I had the problem of stop-start not working 18 months ago on my 2014 XF 2.2D 200, I left it for a while as I am not a fan of S/S anyway. However, at my last service I asked Marshall Peterborough to check the batteries. They informed me that the main battery needed to be changed to sort out the problem. However, when they wanted to charge me nearly £400 for this work, I took it to an independent garage in Milton Keynes who changed it for less than £250. However, afterwards the stop/start was still not working, so I did some research and replaced the small battery myself with the same part number as the Jaguar battery for less than £50. Stop/start immediately working again. Very frustrating as it meant the original main battery had been fine and hadn't needed changing. Very poor call by Marshall Peterborough, who otherwise had given good service. So, from this I strongly advise anyone with a non-functioning stop/start system to change the small battery first. It was pretty easy and rigging up a 9 volt battery with crocodile clips across the terminals during the swap over seemed to maintain my settings.