Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
Mass movement sensor module (MMS)
The mass movement sensor module (MMS) is located in the roof under its own panels. There is one mass movement sensor module (MMS) in the S60/S80/V70/XC70. The sensor is located in the center of the roof.
The two sensors in the XC90 are located along the front edge of the roof and in the roof above the cargo compartment.
The mass movement sensor module (MMS) is used to detect movement in the passenger compartment when the alarm is activated.
When the alarm is activated, the upper electronic module (UEM) carries out a check of the sensors.
The sensors communicate serially with the upper electronic module (UEM). If two sensors are installed, these are connected in parallel to the upper electronic module (UEM).
When the sensors are activated, they transmit microwaves into the vehicle. The microwaves bounce back from the interior of the vehicle and the sensors react to variations in the rebounding waves. A system that uses microwaves is more stable than a system that uses ultrasound sensors and reduces the number of false alarms. For example, microwaves are not affected by the changing temperature of different layers of air inside a vehicle parked in the sun. If the vehicle is exposed to outside microwave interference, a false alarm may be triggered. The cause of the alarm can be read off and verified via VIDA.
The mass movement sensor module (MMS) is powered and grounded via the upper electronic module (UEM).
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.
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