The ignition coil transforms the voltage from the battery to a voltage necessary to create the electrical spark at the spark plugs, thus igniting the fuel. Depending on the model, the coil may have an internal resistor or rely on an external resistance wire to limit the current flowing to the coil from the 12 volt supply.
More advanced electronic ignition systems use power transistors, which deliver pulses to the coil. Some models use a coil for each cylinder of the engine, thus eliminating the use of spark plug wires.
The Powertrain Control Module (PCM) constantly monitors the ignition coil “B” circuit, and if a fault is found within the circuit, the DTC P2305 OBD2 code will be stored.