2015 Volvo XC70 Alarm system service required
 

Hi everyone. I got this error plus some random alarming. The code is DTC CEM-B1D1787. It is probably the alarm siren battery. Here is a useful article on this forum:

https://www.volvoforums.org.uk/showt...siren+location

There is lots out there on removing the siren on older model Volvos, but little on this model. The article above implies that the siren is located under the cowl between the firewall and windscreen, but I would be very interested to hear more detail if any one has replaced or repaired it and how they did it.

Incidentally i bought a Vgate iCar Pro Bluetooth ELM327 adaptor (under £30) which when used with IOS Car Scanner Pro App (£6.99, I think) seemed to work very well.

The siren on older models is the same as the one used on newer ones, more or less. The only difference is some of the siren casings are metal & some are plastic. Also, the siren on older models was underneath the wheel arch liner. On your model, its underneath the scuttle panel that runs underneath the bottom of the windscreen.

Either you need to cut it open to replace the battery inside (cheapest option), or buy a new siren unit if you don't fancy cutting your existing one open (Costs around £150). If you do open the siren & you notice that the circuit board is fried, then you'll need a new siren unit because replacing the battery when the circuit board is fried is pointless. If you do decide to fit a new siren unit, then its a case of plugging the old one out & fitting a new one... simple as that really.

This video shows how to open the siren. Just note, the siren on your car is underneath the scuttle panel & not underneath the wheel arch liner.

https://www.youtube.com/watch?v=vm_qGUegzw8

The siren was behind and above the front left wheel behind the plastic wheel arch. Easy to access and remove, once you find it!

I opened the siren (metal type) by a quick grind on the spot welds and a tap with a punch. Jimmied the plastic siren out, cracked it open by tapping around the seam with a knife and replaced the 2 x aaa cordless phone type batteries with new ones. I had to splice the cables as I couldn’t match the connector. Easy refit.

I now have silent alarms with flashing hazard lights and still have the Alarm System Service Required error message. Could this be an internal sensor issue, I wonder…

What was the condition of the circuit board inside the siren? If its all corroded, new batteries won’t solve the issue... its a new siren you need.

I suggest checking the condition of the circuit board.

Have you replaced the battery with one of a similar output? The batteries have their spec printed on the plastic "wrapper" that holds the cells together.

Hot News - its fixed! The I ran the car for 2 hours and the message has now cleared and there are no false silent alarms and associated quick flashing red LED on the dashboard. I really cant say what I did to clear the error - but after the long run it seems to have vanished. So the battery was definitely the issue and I had assumed the circuit board might be faulty too, but it seems not (there was no battery leak or associated damage to the board). Thank you all for all of your help with this. For the price of an app, OBD2 Bluetooth reader and about a fivers worth of batteries, this fault has been fixed. I wonder what the dealer would have charged?

£125 and an hours labour. About£200. You can feel rightly smug! :teeth_smile:

Perhaps the new rechargeable battery was flat and the drive gave it a chance to charge and give the system the correct voltage to clear the fault.

Dealer fix would have been the diagnostic cost plus a new siren plus labour so wouldn't surprise me if the bill had approached £400.

That's what I like to hear.

Well done!

Final update
 

Annoyingly I got sporadic error messages back again. Thinking that the circuit board may be the issue, I ordered a used siren module for £20. No further errors 2 weeks later - so even if the circuit board looks good, it may not just be the battery causing the problem!