Ignition Coils

What is an ignition coil and where is it located?

The ignition coil, also referred to as a "spark coil" or "spark plug coil," is a critical component in the electrical ignition system of your vehicle. The coil essentially converts the 12 volts from your battery to the thousands of volts necessary to allow for the spark plug to ignite the air / fuel mixture in the engine. The location and appearance of the engine’s ignition coil is dependent on what type of ignition system your vehicle uses, but they can usually be found near the spark plugs. The function of the ignition coil remains the same.

There are two primary types of ignition systems commonly used in modern automotive applications: mechanically timed and direct ignition. Mechanically timed ignition systems were at one time the standard in the automotive world, however they are becoming less common as most modern vehicles are now equipped with a direct ignition system.

Mechanically Timed Ignition

Mechanically timed ignition systems use a distributor to control the ignition firing sequence. In these systems, the engine’s ignition coil may be located remotely and transfer the current to the distributor through a wire, mounted either internally under the ignition cap or on top of the cap (as in GM HEI systems).

Direct Ignition

Direct ignition systems (also known as distributorless ignitions) use a camshaft or crankshaft position sensor (or combination of the two) to control the ignition firing sequence. There are variations on the location and appearance of the engine’s ignition coil (or coils) within the system depending on the vehicle. Some vehicles will use a single ignition coil pack assembly or multiple coil packs, which may be mounted on the engine, that use individual ignition wires to transfer the current to each spark plug. Other vehicles use individual coil-on-plug coils (also known as C.O.P.) which are usually bolted to the valve cover on top of each spark plug and transfer the current directly to the plug through a coil boot. There are also some waste spark ignition systems which use a coil-on-plug style coil, but have an additional wire that connects to the opposite spark plug.

Ignition Coil Failure

The common causes of ignition coil failures are heat and age.  An engine’s ignition coil can suffer a complete failure, resulting in no spark; or may become too weak to supply sufficient current to the plug to adequately ignite the air / fuel mixture in the engine which may result in poor performance and a misfire condition.  In either case, the car engine’s ignition coil must be replaced. OBDII Check Engine Codes related to ignition coils include:

P0300 Random/Multiple Cylinder Misfire Detected
P0301 Cylinder 1 Misfire Detected
P0302 Cylinder 2 Misfire Detected
P0303 Cylinder 3 Misfire Detected
P0304 Cylinder 4 Misfire Detected
P0305 Cylinder 5 Misfire Detected
P0306 Cylinder 6 Misfire Detected
P0307 Cylinder 7 Misfire Detected
P0308 Cylinder 8 Misfire Detected
P0309 Cylinder 9 Misfire Detected
P0310 Cylinder 10 Misfire Detected
P0311 Cylinder 11 Misfire Detected
P0312 Cylinder 12 Misfire Detected
P0314 Single Cylinder Misfire (Cylinder not Specified)
P0350 Ignition Coil Primary/Secondary Circuit Malfunction
P0351 Ignition Coil A Primary/Secondary Circuit Malfunction
P0352 Ignition Coil B Primary/Secondary Circuit Malfunction
P0353 Ignition Coil C Primary/Secondary Circuit Malfunction
P0354 Ignition Coil D Primary/Secondary Circuit Malfunction
P0355 Ignition Coil E Primary/Secondary Circuit Malfunction
P0356 Ignition Coil F Primary/Secondary Circuit Malfunction
P0357 Ignition Coil G Primary/Secondary Circuit Malfunction
P0358 Ignition Coil H Primary/Secondary Circuit Malfunction
P0359 Ignition Coil I Primary/Secondary Circuit Malfunction
P0360 Ignition Coil J Primary/Secondary Circuit Malfunction
P0361 Ignition Coil K Primary/Secondary Circuit Malfunction
P0362 Ignition Coil L Primary/Secondary Circuit Malfunction

For an even more in-depth explanation of the different types of ignition coils that there are, causes and symptoms of failure, and much more, check out our ignition coil guide for cars and trucks.

Can I replace the ignition coils by myself?

The ignition coils can be replaced by the typical do-it-yourselfer depending on the vehicle. Some vehicles' engine setup might make it a little difficult to access some coils and may require the additional manuevering of other parts. Make sure the engine is cooled down before attempting the repair to prevent burns. It's a good idea to mark which spark plug wires are which. Remove the spark plug wire to the ignition coil you want to replace. Then remove the bolt that holds the coil to the engine. The coil will then pull up and off. This procedure can differ depending on the vehicle, so following a repair manual or online instruction guide for your specific vehicle can be extremely helpful.