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Discussion Starter · #1 ·
Car is a 2016 XC90 T6 Inscription. Only a few weeks after buying it my wife noticed the start/stop was no longer working. I know many people wish they could turn it off permanently but my wife really likes it. Her car is the Mom Taxi and having start/stop really helps fuel economy driving around town and while waiting in the car for various sports/dance pickups.

She brought it to the dealer and they said they did a bunch of software updates. It worked as I drove it home. The next day...didn't work. From that point on there is the random trip it works but 95% of the time the "Ready" on the dash is greyed out and it doesn't work.

I read all the operating conditions in the manual. No issues there. We've had it in all weather, all types of trips, all types of driving conditions. Won't work. She's at 8900 miles and we're waiting for the 10k service to bring it in.

Here's what blew my mind though. The start/stop hasn't worked in weeks. I borrowed her car on Sunday to drive up to the mountains. 1hr 30min drive there. Didn't work...as I expected.

After skiing all day we get back in the car. It is TWENTY THREE degrees F outside. So cold the doors were frozen stuck.

I start the car, drive about 2 minutes, then stop to turn out of the parking lot. Start/stop kicked in!!! The car wasn't even warmed up yet and it was 23 out!!! I actually thought it stalled since it was so weird to have it come on at that moment.

Rest of the drive home...ready indicator was on and start/stopped worked. Monday and Tuesday, back in the lowlands, no Start/Stop. Am I missing something here? What could cause such sporadic performance?


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Was the outside temperature reading correct? I guess it was as you saw it. But if it did stop/start at low temperature then something is not right. Maybe the engine temperature reading sent to the computer was not right?

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Car is a 2016 XC90 T6 Inscription. Only a few weeks after buying it my wife noticed the start/stop was no longer working. I know many people wish they could turn it off permanently but my wife really likes it. Her car is the Mom Taxi and having start/stop really helps fuel economy driving around town and while waiting in the car for various sports/dance pickups.

She brought it to the dealer and they said they did a bunch of software updates. It worked as I drove it home. The next day...didn't work. From that point on there is the random trip it works but 95% of the time the "Ready" on the dash is greyed out and it doesn't work.

I read all the operating conditions in the manual. No issues there. We've had it in all weather, all types of trips, all types of driving conditions. Won't work. She's at 8900 miles and we're waiting for the 10k service to bring it in.

Here's what blew my mind though. The start/stop hasn't worked in weeks. I borrowed her car on Sunday to drive up to the mountains. 1hr 30min drive there. Didn't work...as I expected.

After skiing all day we get back in the car. It is TWENTY THREE degrees F outside. So cold the doors were frozen stuck.

I start the car, drive about 2 minutes, then stop to turn out of the parking lot. Start/stop kicked in!!! The car wasn't even warmed up yet and it was 23 out!!! I actually thought it stalled since it was so weird to have it come on at that moment.

Rest of the drive home...ready indicator was on and start/stopped worked. Monday and Tuesday, back in the lowlands, no Start/Stop. Am I missing something here? What could cause such sporadic performance?

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I have an S60 (So Jealous of your XC 90), and I use Start / Stop. Start / Stop will only engage under operative conditions where it's not too hot or not too cold. Otherwise, the car will function on Fuel. The fact it kicked on at 23F is very weird, especially since the car wasn't "Warmed Up".

My Suggestion: Don't want until the 10K Maintenance to fix when the "Gremlin" is happening now. My luck has always been that the problem "self-corrects" the day you want the dealer to see. So I'd suggest your wife take it down the dealership now, while the problem frequent, and ask a service tech to come on a test drive.
 

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There are a few existing threads about this issue. The most common conclusion is that the XC90's alternator can't keep up with the electrical needs of the car unless you take longer trips. If the battery drains beyond a certain point, start/stop is disabled. Try charging the battery overnight and see if start/stop behaves normally. That worked for me.
 

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I can only get start/stop to work if I charge the battery overnight on a trickle charger. I think Volvo has a battery / alternator issue. I used to get a low battery warning but after a software update the warning went away, but I suspect they are just suppressing it and they still have an underlying issue.


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If your wife drives mostly in the city, with frequent stops, the battery doesn't get enough charge and the start/stop is disabled. When you drove for a while, the battery had a chance to get recharged and that is why it was working again. On your drive home, if you drive over a certain speed (never got the actual speed, but somewhere around 110 kms/h to 130 kms/h, or 70 mph to 80 mph) the READY is greyed out.
 

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Discussion Starter · #7 ·
If your wife drives mostly in the city, with frequent stops, the battery doesn't get enough charge and the start/stop is disabled. When you drove for a while, the battery had a chance to get recharged and that is why it was working again. On your drive home, if you drive over a certain speed (never got the actual speed, but somewhere around 110 kms/h to 130 kms/h, or 70 mph to 80 mph) the READY is greyed out.
If this is the case, this is a frustrating reality. We downgraded from a Sequoia and one of the main reasons was for fuel economy reasons. When you go for test drives they tout start/stop but it seems ridiculous that in order to use it you first have to drive an hour. When you read the "Conditions for Start/Stop" in the manual no where does it talk about not working in around town driving. The website says "exclusive fuel-saving technology like the auto start-stop function reinforces our environmentally friendly approach"...perhaps that should have a disclaimer that it only works 5% of the time for those that do local driving.

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Adding to what others say, my car basically works with Start/Stop for a few days after it visits the dealer (and gets charged), than it stops. Despite some highway trips, most of our trips are neighborhood, and my wife's daily commute is < 3 miles.

I'll add the the weather has to be in your favor for this to work, not too hot, not too cold. Also, things like heated seats, stereo, defrosters, etc. will lower the probability of the system activating.
 

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If this is truly caused by a chronically low battery charge than this seems like a serious engineering failure. I'm not normally a sensationalist but this sounds on par with purposefully evading emissions controls to market a vehicle that claims to use start/stop technology but in common practice is unable to apply it. It's one thing if it's simply a matter of the engine staying on for a bit to reach optimum operating levels, but it's a whole other thing for it to not turn off because the vehicle draws more power from the battery than it can keep up with.

I've got a T8 which seems to be unaffected but if my engine didn't shutdown at a stop I would be absolutely pissed. It is one of the reasons to buy a hybrid. Even on a non-hybrid vehicle start/stop is a feature that is essential to achieving the reported fuel economy and emission levels. For it not to function on a significant portion of vehicles even during optimal environmental conditions because they didn't engineer an effective electrical charging system is simply scandalous.

So the question is whether a weak alternator/small battery is truly the cause of all of this?
 

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Discussion Starter · #10 ·
Interesting update for everyone. Brought the XC90 in for the 10K service and I noted my frustration with Start/Stop. They had the vehicle for 3 days. Here are the notes:
- Verified it wouldn't work
- Installed "Total Upgrade" software, test drove, still didn't work
- Battery state of charge at 58% but registered "good and recharge"
- Charged battery overnight, in the morning only at 60%
- Replaced battery, test drove vehicle, STILL didn't work with a new battery
- Escalated the issue to a "field technical specialist" who found a TJ on a foot detection module (tailgate) that would create a low battery state of charge problem.
- Replaced foot detection module with updated part.
- Start/Stop now working

I have hope this may have been the issue. Start/stop has worked all day. Will report back if it goes bad again.

For those of you who are having problems, you may need your foot detection module replaced!!!
 

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If this is truly caused by a chronically low battery charge than this seems like a serious engineering failure. I'm not normally a sensationalist but this sounds on par with purposefully evading emissions controls to market a vehicle that claims to use start/stop technology but in common practice is unable to apply it. It's one thing if it's simply a matter of the engine staying on for a bit to reach optimum operating levels, but it's a whole other thing for it to not turn off because the vehicle draws more power from the battery than it can keep up with.

I've got a T8 which seems to be unaffected but if my engine didn't shutdown at a stop I would be absolutely pissed. It is one of the reasons to buy a hybrid. Even on a non-hybrid vehicle start/stop is a feature that is essential to achieving the reported fuel economy and emission levels. For it not to function on a significant portion of vehicles even during optimal environmental conditions because they didn't engineer an effective electrical charging system is simply scandalous.

So the question is whether a weak alternator/small battery is truly the cause of all of this?
I doubt there's anything going on beyond a design problem - and it's only a problem for those who want SS to work! For me having SS disabled would be a valuable feature, one that I would pay extra for ($500-1000.)
 

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Interesting update for everyone. Brought the XC90 in for the 10K service and I noted my frustration with Start/Stop. They had the vehicle for 3 days. Here are the notes:
- Verified it wouldn't work
- Installed "Total Upgrade" software, test drove, still didn't work
- Battery state of charge at 58% but registered "good and recharge"
- Charged battery overnight, in the morning only at 60%
- Replaced battery, test drove vehicle, STILL didn't work with a new battery
- Escalated the issue to a "field technical specialist" who found a TJ on a foot detection module (tailgate) that would create a low battery state of charge problem.
- Replaced foot detection module with updated part.
- Start/Stop now working

I have hope this may have been the issue. Start/stop has worked all day. Will report back if it goes bad again.

For those of you who are having problems, you may need your foot detection module replaced!!!
I had this done two days ago (Technical Journal 32162) on my 2017 T6 at the Volvo dealer:

"Low battery State of Charge due to FMDM disturbance, Item:TJ32162.1.0-2016-12-20"

Start/Stop still does not work. Large battery drain still takes place based on my measurement of battery voltage from the connecting points in the engine department
 

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We had this happen on both of our XC90s. My wife's which is a 1 year old had it happen a few weeks ago and sure enough it is the battery. There was not enough charge left in it. My XC90 has now also went dead and only after 6 months. They ended up replacing the battery in my wife's car and mine is now in the shop which will require the same thing. I just think the car drains so much power in "standby" mode and the constant start/stop worries me with the alternator and the battery.
 

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Which battery was replaced, just curious, as I am not sure how much the main 12V, has to do with with start stop during the stop, only being used when the car "starts". The front battery is supposed to run all the brains, accessories, etc. especially in start stop operations, and is there to "reduce" the load off the the main 12V. On my T6, when start stop works, and you hit the gas, it's quite apparent that the engine is starting up so I assume at that time the 12V is used, however with a good alternator, that pull/drain should be readily replaced.

Per a conversation I had with a Volvo tech, Volvo designed the new cars with the 2 batteries based on experiences other companies have had using only 1. He had been to a 4 day class on the east coast, and there was supposedly quite a bit discussed on the start/stop, and how much drain would be placed on just a single battery, especially in situations were you are sitting in either a slow traffic situation where stop/stop would be used a lot and or a lot of city traffic. The front battery is a different type of design, some form of wrapped cell, the rear battery outwardly looks just like most 12V cells.

I have asked through my dealer, which battery is being referenced with the 12V error, and they claimed it was the rear only. I also asked what the voltage of the front battery was but dealer did not know and forwarded it on to Volvo tech line.

Paul Caldwell
2017 T6 XC-90
 
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