Coil On Plug (COP) Ignition Coil. Ignition System.
An induction coil, placed on each sparkplug of a vehicle and used with and ECU and a Camshaft or Crankshaft position sensor for timing, to transform a vehicles battery voltage to a much higher voltage needed to create proper spark in the spark plug.

-1999 4CYL EXC B4184SM. 2000- 4CYL EXC B4184SM.
Ignition Coil
A failed ignition coil in your 2001 Volvo can lead to anything from an intermittent misfire to a car that won't start.