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.
Control Module
The primary task of the upper electronic module (UEM) is to manage the functions of the:
- Siren (SCM) (XC90, applies up to and including structure week 201127)
- Sun roof
- Mass movement sensor module (MMS) (does not apply to the XC90 MY 2012-)
- Ultrasonic sensor module (IMS) (only applies to the XC90 MY 2012-)
- Rain sensor module (RSM)
- Interior roof lighting
- Cargo compartment lighting (V70 and XC70)
- Sun visor lighting
- Remote control
- Automatic rear view mirror anti-dazzle
- Seat belt reminder
- Tire pressure warning
- Indication of disconnected passenger airbag (PAD- Passenger Airbag Deactivated)
- Compass
The control module is integrated in the rear view mirror. If the control module is replaced, the rear view mirror assembly must also be replaced.
The upper electronic module (UEM) communicates with directly connected components and with other control modules and components via serial communication and the controller area network (CAN).
The control module checks activations and input and output signals via an integrated diagnostic system. A diagnostic trouble code (DTC) is stored if the control module detects an error. In certain cases the upper electronic module (UEM) replaces the faulty signal with a substitute value.
Any diagnostic trouble codes (DTCs) are stored in the control module memory. The data can be read off using VIDA (Volvo scan tool).
A simple way to check that the upper electronic module (UEM) is supplied with power is to activate the seat belt reminder function. Activate the seat belt reminder by sitting in the driver's seat. Switch on the ignition, do not fasten the seat belt. If the seat belt reminder lights, the upper electronic module (UEM) is supplied with voltage. Another way of checking that the control module is supplied with voltage is to switch on one of the rear reading lamps.
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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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