Ignition Coil: Description and Operation

The ignition coils are triggered by the powertrain control module in pairs (cylinders 1 and 4 and cylinders 3 and 2) sending one ignition spark to the firing cylinder and one ignition spark to the corresponding cylinder on the exhaust stroke. This makes sure that any unburnt fuel residues remaining in the cylinder on the exhaust stroke are re-ignited to provide cleaner exhaust emissions.