NOTE: Right-click on any image and open in a new browser tab if you want to see them larger. As always, use discretion when programming your vehicle. The instructions that follow are provided for assistance only. If you are unsure of what you are doing, please do not proceed.
The alarm was going off at random in the 2005 Volvo V50 every week or so without provocation. Although on this model there does not seem to be a way to disable the alarm with a software update, one can definitely determine the causes of the alarm.
First, common causes of an erroneous security alarm activation:
- Interior motion sensor (a moth or a fly inside the car can set it off, it’s in the sunroof control area).
- A bad battery or ground can cause the siren to alarm. A bad battery can cause almost anything strange in a Volvo, I’ve determined.
- Any bad or intermittent sensor on the doors or hatch can trigger the alarm. If the car thinks it is being broken into, it will sound the alarm. The replacement process for this part is labor-intensive.
- The SCM or Siren Control Module can be the culprit.
- The siren has a sealed battery that will eventually leak after 8-10 years.
Utilizing VIDA/DiCE to check for alarm activation causes:
- Launch VIDA and connect DiCE unit. Verify vehicle specifics.
- Navigate to the main “Diagnostics” tab.
- Click the “Vehicle Communication” tab that results (see image above).
- You will be presented with a diagram of all of the modules that are active in your vehicle, as seen in the image above.
- The green blobs are the different modules in the car; click on them to see what they do. Note that in your vehicle your modules may not be green. This is not necessarily cause for alarm. Certain modules will log a fault which will change the color of that module. The modules tend to end in the letter “M” for module. CEM is Central Electronics Module. BCM is Body Control Module. TCM is Transmission Control Module, etc.
- Click on the CEM module inside the vehicle diagram.
- On the bottom half of the screen you will see a set of tabs. Click on “Advanced”.
- Click the + symbol to expand all of the CEM options.
- Select “reading off the alarm cause”
- Click on the “VCT2000” image to begin.
- A window will appear with the causes of the alarm activation. The first ones in the list are the most recent.
My results below were suggestive of the left rear door (handle/deadbolt assembly). Your results will depend on the source of your alarm activation.
A simple workaround, if you are inclined to disable the alarm system, is to remove fuse F56 for the SCM (passenger side underneath the dash, or driver’s side if you’re in Britain). Please note that from this point forward if you disable the alarm you will be prompted with a message on the MID to service the alarm system each time you start the vehicle, which you can acknowledge with a press of the turn signal stalk.
If you are so inclined to go further, there is the electrical wiring diagram. This one is applicable to my vehicle with a build date of 09/2004. Keep in mind that the EWDs changed three times even for the 2005 model year alone, so yours may vary.