Here's info from the 2007 MK (US) Service Manual:
P0302-CYLINDER 2 MISFIRE
Any time the engine is running and the adaptive numerator has been successfully updated.
If the Powertrain Control Module (PCM) detects that the variation in crankshaft speed between each cylinder exceeds a calibrated value, based on engine rpm and load, a fault is set.
FUEL DELIVERY SYSTEM
IGNITION COIL, WIRING, OR CONNECTORS
ECT SENSOR, WIRING, OR CONNECTORS
MAP SENSOR, WIRING, OR CONNECTORS
O2 SENSOR, WIRING, OR CONNECTORS
ENGINE MECHANICAL SYSTEM
POWERTRAIN CONTROL MODULE (PCM)