When the key is turned to the “on” position, power is sent to the coil pack and voltage is built up and stored until it receives a signal from the PTU telling it to release the voltage through the coils. At this point voltage is sent through the spark plug wires and into spark plugs which create the spark inside the combustion chamber. A DSM coil pack consists of two coils. Cylinders 1 & 4 are on one coil, and cylinders 2 & 3 are on the other.


  • Spark on only cylinders 1 & 4 or 2 & 3
  • Misfire
  • No spark


There is several methods for testing a coil pack.

  1. Swap out with a known good unit,
  2. Screw driver method.
    1. Remove spark plug boot from cylinder head
    2. Insert metal end into boot making contact with the metal clip inside.
    3. Holding by the handle, put the metal part of the screwdriver about 1/4 over the intake manifold.
    4. Have a friend crank the car over and see if any sparks jump from the screwdriver to the manifold
  3. Test for resistance using an ohm meter.


There is an aftermarket setup that will replace the coil pack. It is called Coil-on-Plug. It plugs into the factory coil pack pigtail and bolts on in place of the spark plug cover and eliminates the spark plug wires giving each cylinder its own coil directly over the plug well. This is said to be more efficient and it can help clean up the engine bay. There are several aftermaket units available depending on preferance.