Hi. I have a 2013MY V40 and it runs very well even though it’s 10 years old, but two problems have appeared. 1. The key fob works very weakly and takes several button presses and the keyless entry has stopped working at all. 2. The stop start has stopped working. I wonder if these problems could both be linked … perhaps through the auxiliary battery? Is there any chance I could solve both by replacing the auxiliary battery (and possibly the main battery too?)? Thanks.

 

My 2015 xc70 remote range decreased to nothing, keyless stopped working and starting getting low tire pressure system warnings. The antenna for those systems was bad. #3 on the diagram. That antenna is used on most Volvos with keyless entry since 2004. It's mounted between the roof and the headliner.
I would test the batteries in your remote first.

No suggestions for your stop start but could be a weak aux battery if it's original.

 

Thanks Hoonk. I hadn’t thought of the antenna. Sounds like it’s likely to be an expensive investigation to ask the Volvo dealer to do though, judging by the high price they quoted me for reprogramming and for new key fobs (although I doubt it’s the fob because both of mine behave equally weakly, even with new batteries fitted in them). I wonder if there’s anyway I can check if it’s the antenna at all? Thanks again.

 

The first symptom was a TPMS system service needed, or similar warning. Not a low tire warning, it was a low tire warning system malfunction. Don't know if TPMS is standard in your country. After that the remote and keyless entry slowed then stopped.

I replaced the antenna with a used part, from a local junkyard - you have to partially drop the headliner to get to it, took about 45 minutes to replace.

 

I also have the same set of issues, though not as bad as yours. Makes me think it must be linked...
Start-stop works after long trips, but the engine always turns itself back on after a couple seconds, even when I'm not moving. Doesn't work at all the vast majority of the time though.
Keyless entry for the front two doors doesn't work, but the back two still work.

No other issues with the car.

Have you had any luck fixing it?