Central Electronic Module (CEM): Function: Horn
WARNING: This page is about a different car, the 2010 Volvo V70, 2009 Volvo V70, and 2008 Volvo V70. However, it is still accessible from the selected car via links, so may be relevant.
The horn (16/10-11) is located behind the radiator grille. The horn is supplied power from the horn relay (2/17) in the engine compartment fuse and relay box. The horn is activated when a switch in the steering wheel is closed. The closure is detected by the steering wheel module (SWM) (3/130), which sends a signal to the central electronic module (CEM) (4/56). The central electronic module (CEM) forwards a ground closure on one of its outputs, grounding the signal horn relay and activating the relay.
The horn is grounded in the body.