What Cause Check Engine Light Flashing: Cause by These 3 Components


When the check engine light is flashing while you are driving or starting your vehicle. You need to stop the vehicle and pull over on the side of the road immediately.

When the check engine light is flashing because you have one severe misfiring cylinder or in one bank. A misfiring engine is cause by one of these component, such as ignition (spark plug or ignition coil), air (intake or exhaust valve is not properly closed and/or intake), and fuel (faulty fuel injector).

An internal combustion engine is requiring three crucial groups of components. These components including air, fuel, and ignition. If you want to learn more about each component. Read more below for more details.

An Internal Combustion Engine Requires Three Group of Components:

Air/Compression

Air is being drawing from the air duck to the intake manifold and into the cylinder. The air is being drawing into the combustion chamber by the piston. If the cylinder is below compression specification according to the vehicle manufacture will cause check engine light to flash. For example, if the compression test in cylinder number one is 100 psi, but the manufacture specification is 150 psi. The main components can cause low compression are piston rings, intake valve, and exhaust valve.

Fuel System

The internal combustion engine fuel delivery system consist of fuel pump, fuel filter, and fuel injectors. The only faulty injector can cause misfiring and cause the CEL (Check Engine Light) to flash. In some rare occasion, fuel pump and fuel filter can cause the engine to misfire. A clogged fuel filter can cause the engine to misfire. Furthermore, a weak fuel pump can cause the engine to misfire too.

Ignition System

The ignition system components are spark plugs, ignition coils, and ignition wires. For older vehicle the ignition system is different. And it has distributor, distributor cap and rotor. A faulty spark or ignition coil will cause the engine to misfire and the check engine light will be flashing.

How to fix a flashing check engine light?

If you have a little knowledge do-it-yourself personality or have little know how to repair some mechanical on a vehicle. Then you have no problem diagnosing the flashing check engine light.

The tools and knowledge how to fix flashing check engine light are a OBD (On Board Diagnostic) scanner with mode 6 available, OBD scanner not OBD code reader (OBD code reader is not useful), spark plug socket, 3/8 racquet, a set of 3/8 sockets, and compression tester. Follow all the steps below:

  • Step 1. Plug OBD code scanner into DLC (Diagnostic Link Connector) this connector is usually located under kick panel of driver’s side.
  • Step 2. Retrieves the code from OBD code scanner. The code should be P0XXX. If the code from OBD scanner is P0302 that indicates the cylinder number 2 is misfiring.
  • Step 3. Now go to service repair manual look up make and model according to your vehicle. Find the number 2 cylinder location.
  • Step 4. The easiest thing to do is switch the ignition coil from cylinder number 2 to the neighbor cylinder. The reason doing this to see the misfiring move. If the misfiring moves to the neighboring cylinder which mean the ignition coil is faulty and replace that ignition coil.
  • Step 5. If the misfiring is not move when you move the ignition coil. The Next step is to move the spark plug.
  • Step 6. After the spark plug moved and the misfiring is not moving to the neighboring cylinder. That mean the spark plug is good. If the misfiring moves to the neighboring cylinder after you moved the spark plug which mean a faulty spark plug. If the misfiring is not move the next step is to do compression check.
  • Step 7. You need to disable the fuel system in order to do the compression test. Because if you do not disable the fuel system it will ruin your compression tester. Removes the spark plug and puts the compression tester to the misfiring cylinder. Crank the engine over for 5 seconds with wide throttle open. Once done compare the compression value to manufacture specification.

Why is my check engine light flashing and care shaking?

The car is shaking means that the vehicle has a dead cylinder. For example, if the vehicle has 4 cylinders and one cylinder is completely dead now the vehicle is running on 3 cylinders. Once again can cause by a faulty spark plug, or ignition coil or low compression.

If the vehicle starts to behave this way such as shaking and the check engine light flashing you need to pull over the road and turn the ignition of completely.

Here is more information about check engine light.

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