V40 Stop Start Service and no Front wipers (again!)

[Vogalogue]

Hi all,

New to the forum, but an old time forum user (used to run a supra forum and have spent many hours on various car forums in the past!)

A bit of background: My other half has had a 2012 Volvo V40 for about three years and recently it's all started to go wrong. Started with "gearbox noises" which I thought was the release bearing, but on removing the gearbox it was the input shaft bearing, rebuild the gearbox and put it together but found once back on the road we had new electrical issues.
I wasn't involved in the gearbox removing and replacing, but the rebuild was a team effort that I was involved with. I trust the guy that removed and refitted the gearbox (brother in law) and he says apart from disconnecting the battery (2 weeks), the car wasn't jump started, charged, earths looked ok etc. This shouldn't be related, but worth mentioning.

The car drives perfectly now apart from...

On start up there is a dash message saying "Stop Start Service required" and the system is disabled, the reason in the menu is "battery charging". - we have also noticed that the front windscreen wipers don't work. Although this seems highly odd, from forum searching and googling it is not uncommon for this model.

Reading on the forum it looked like it may be an issue with the support battery, which I didn't know the car had. I replaced the main battery within the last couple of years, reset the BMS and all was well (Start stop didn't work when we first got it, new battery and reset sorted that). I replaced the support battery (AGM type as suggested YAUSA one from Halfords) checked that the main battery was fully charged via trickle charge, reset the BMS using the "cheat code" of light switches until the battery light flashed three times and was disappointed to see that there was no change. the original Volvo aux battery removed actually was holding a charge so I don't think that was the issue but I was so "committed" after half removing the bumper I decided to fit the new one.

Further googling showed a video and a Volvo service bulletin saying turn the ignition on, disconnect the BMS sensor wait then reconnect. do this the wipers armed! but on reconnecting ran constantly, even with the car locked.

Currently the car isn't really useable, - if I disconnect the BMS sensor the wipers work as usual, stop start doesn't, obviously.. but I don't want to run the car like that in case the BMS over / undercharged the battery (I'm not sure how much that manages vs plain old fashioned alternator regulation. The other half also reported the clock keeps getting reset when she starts.

I don't have VIDA, but fault codes logged and clear to immediately return are:

• B139F(01) - Main battery relay-general electrical failure short to ground
• B129A(88) - invalid data from the Driver Side Windshield Wiper Motor over the LIN
• B10AD(96) -Rain Sensor Value of Signal Protection Calculation Incorrect.
• U1007(00) - Lost communication With Battery Monitoring Sensor 'A'.

• I've reset the BMS multiple times by using the light flashing technique.
• I've reset by unplugging the sensor with the ignition on.
• I've checked fuses (wipers were all ok, as are the larger ones on the battery and above the fuse box)
• Checked the aux battery charge fuse - also passed a voltmeter gets a decent voltage (its new!)
• I've trickle charged the main battery then reset the BMS
• I've reset then left it locked overnight to allow full system shut down
• Main battery presumed good as sub 2 years old and shows over 12v after being parked overnight, 14.4v with the engine running.

I'm a loss where to go from here, any ideas or experience please? I am wondering if it is the BMS sensor itself (or the wiring to it, which looks fine). I've ordered a used one with replacement earth straps to swap over and see if it makes a difference.

Is there away to test the sensor off the car? (can't see anything on google)

Thanks in advance!