Start-Stop not functioning - what to do

[AndrewH]

Hello,
My Peugeot 508 SW GT (2016) 2 litre HDi appears to have a fault with the Start-Stop function. I had a new Battery Protection Module fitted by my dealer (best part of £400) which at least helped with some of the related minor problems - lots of error codes.
I also have a new Bosch battery - a proper one for the start stop function.
Even after a long run, the Start-Stop very infrequently activates. The one thing I noticed when putting a battery condtioner/charger on it after a long run was that the battery was measuring just 12.1 volts. After charging up the start-stop works - but just for a short time.
Does anyone have any suggestions, please ? I'm reluctant to go back to the dealer - it's £100 just to sniff the car.
I've just bought an OBD II code reader which I'll get to grips with.

[GiveMeABreak]

First thing is when you replaced the car battery, what battery specifications are the battery? What Type, AGM, EFB for example and what is the info on the label. If you can provide that with your VIN I can check if you have the correct battery or not and also which other components that may be installed, as there are different variations of Stop Start. Please post your VIN in full without spaces - it will be automatically masked from public view after submitting your post & will only be visible to staff.

The battery charge status unit holds the type of battery information relevant to the battery fitted and provides fine tuning of the energy management system for the BSI amongst other things.

[AndrewH]

Thank you.
The battery is Bosch S5A08 Start-Stop AGM 70Ah 760A Type 096 12V
The VIN is VF3**************[VIN obfuscated, can be read by forum staff]

[GiveMeABreak]

Ok 2 things to note:

1) Your original car battery specs are ok, apart from the original being an EFB (Enhanced Flooded Battery) type and you have replaced it with an AGM. This is generally OK as an AGM is superior and your car's battery management system should work fine with it.

2) Your vehicle is fitted with the older Stop Start system which actually has a completely separate system for this operation. Hidden behind the front left wing there is an Ultra-Capacitor / Energy Accumulator and a network voltage maintaining device that converts the energy and manages the system.

So I'm surprised your dealer didn't think to check this or diagnose it, as they have a finite service life. If the ultra-capacitor is no longer storing energy, it can of course affect the Stop Start system. I don't recommend you go hunting about for it as these can still pack a wallop and must be discharged using specialist equipment before removal.

[AndrewH]

Marc -

thank you for your expert views.

I'll get the OBD II reader on it today and see whether there are any error codes.

Can you tell me, please, if the fact that the stop-start is not working correctly would have adverse effects on performance ? One thing I've noticed it the HDi 2 litre blue diesel engine is giving me 47 MPG overall, which is a bit disappointing. Over 50 MPG on a quiet motorway run. But perhaps that's normal.

Andrew

[RichardW]

The PSA systems works for about 5 minutes with a new battery - just ignore it after that. Th amount of fuel it saves is miniscule, and doesn't justify the wear on the re-starting components!

[GiveMeABreak]

Marc -

thank you for your expert views.

I'll get the OBD II reader on it today and see whether there are any error codes.

Can you tell me, please, if the fact that the stop-start is not working correctly would have adverse effects on performance ? One thing I've noticed it the HDi 2 litre blue diesel engine is giving me 47 MPG overall, which is a bit disappointing. Over 50 MPG on a quiet motorway run. But perhaps that's normal.

Andrew

I have a 1.5 Blue HDi and you'd expect better MPG, but no. I live is a hilly rural area, no motorways or dual carriageways and am lucky to get 43-47 on terrible roads. That's with Stop & Start that doesn't work because on mine that uses the main vehicle battery only (no ultra-capacitor) it has to be at 80% minimum charge to operate and I don't use the car daily, perhaps once a week - so the time it's sat doing nothing the battery is discharging below the threshold required because of the Alarm, internal sensors, Hands free system proximity checks etc.,. The only time mine ever works is if I charge the battery back up and it may work 4 or five times that week, then stops again.

It's really no good in winter periods when the battery is in demand and constant use for heating and cold starts.

As Richard says, I'd just ignore it to be honest for the little it is going to save versus the extra wear on expensive components like the starter and alternator.

[PaulC5]

I am disappointed with our 308sw 1.5 hdi mpg, a lot worse than we had on our previous C4 1.6 hdi. As an example going to the Lake District from Lincoln (183 miles at mostly 60 to 70 mph) we used to get 65 to 70 mpg, the 308 is lucky if we get 55 mpg, all going at the speed limits. Its stop/start very rarely works since the battery is never charged enough.

[AndrewH]

Thanks all for the input.

I put the OBD-II fault code reader* on the car - no error codes I could see.

Given that a diagnostic and repair by the Peugeot dealer - ultra high capacitor replacement ? - could easily be £1000, I think I'll pass on that.

*from Streetwise brand, bought at Eurocar parts, just £20. Connects to your smartphone. A no-brainer.

[GiveMeABreak]

Just don't expect that to do much and it won't read anything but basic OBD II codes. Modern cars have a lot of electronic equipment and sensors not covered by generic code readers, so they won't be able to read constructor-specific codes nor some of the later system ECUs, so as long as you know that just because it isn't returning a code, it doesn't mean there aren't any.

But in either case, there are no fault codes for the Stop & Start system as in itself it isn't an independent system, but made up multiple other systems, like the battery, the network voltage maintaining device, the BCSU, BSI, ESP System, Engine ECU, Airbag system (for seat belt connection monitoring), Climate Control ECU, Exterior & Engine temp sensors, and the list goes on

[wheeler]

The PSA systems works for about 5 minutes with a new battery - just ignore it after that. Th amount of fuel it saves is miniscule, and doesn't justify the wear on the re-starting components!

I would agree with that 100%. I would regard the S/S not working as a bonus, would save me manually turning it off every time i get in the car.