Check Engine

The «check engine» light on the dashboard of your car may indicate problems with the quality of the fuel-air mixture or ignition faults, as well as many other things. This icon, a yellow or orange engine icon, means that the ECU has detected a malfunction in one of the vehicle's systems.

Only diagnostics can answer why the check is blinking or burning. To do it, you only need an adapter connected to the ECU connector and a smartphone with installed diagnostic software. However, you can pre-determine the cause of certain symptoms or a number of basic checks of some engine systems.

10 reasons why check engine lights up

  1. The fuel tank cap is open. Check if it is tightly closed.
  2. Bad gasoline. The system may be reacting to the quality of fuel. The solution is to drain the petrol and refill it with better quality gasoline.
  3. Oil level. First of all, check its level with a dipstick. Also look for cracks in the block and oil leaks.
  4. Problems with the gasoline pump or the tank screen. Check to see if the pump is running smoothly, and if it is making any unusual noises.
  5. Dirty injectors. Can be eliminated by cleaning injectors.
  6. Faulty high voltage wires or coils.
  7. Problem with spark plugs. The icon also lights up when there is a problem with the spark plugs. It is worth checking the performance of the plugs and, if necessary, replace them.
  8. Lack of spark in one of the cylinders.
  9. The lambda probe is defective. The problem can only be eliminated by replacing this node with a new one or installing a bumpers, cleaning occasionally helps.
  10. Failure of the catalytic converter. Also solved by replacing the catalytic converter.

Only the main causes and solutions are listed here. In fact, there are many more. Diagnosis of the onboard computer, which controls all systems of the car, can give a more complete picture of the situation.

How to remove the check engine

Let's take a closer look at the steps that must be done first in order to get rid of the Check Engine indicator. The algorithm of priority actions will be as follows:

How to reset Check Engine errors: video

  1. Check whether the gas tank lid is closed. The situation is especially relevant if you have just left the gas station, and soon after that the check engine light came on. This means that either the fuel system is leaking because the tank cap is not screwed on tightly, or the fuel quality leaves much to be desired.
  2. Check the condition of the spark plugs. To do this, unscrew them and visually assess their condition. Very often it is the spark plugs that cause activation of the Check Engine indicator. In particular, the reason may be that they start to leak current due to fouling on the electrodes. Such fouling is formed as a result of the high content of metals or other conductive substances in the fuel. Also, an error may occur if the gap between the electrodes on the plug exceeds the distance of 1,3 mm. We consider separately about the diagnosis of plugs and how to perform it by their color. You will also find it useful to know how to replace them.
  3. Oil level. If the check engine icon lights up only when the engine heats up, stop and listen, you may hear some unusual engine sounds. Use a dipstick to check the oil level in the engine, and top up if necessary. Also check for oil leaks.
  4. If your car is equipped with sensors of technological fluid purity (engine oil, fuel and so on), the indicator may light up if the corresponding indicators exceed the permissible norm. The solution is to replace the relevant filters or completely replace the fluids if they do not meet the standards.
  5. Reset the minus terminal from the battery (15...20 seconds). After that the Check Engine light should go off and the clock on the computer should be reset. This method may be relevant in two cases. The first one is a trivial «glitch» of ECU. The second — if the memory of the electronic unit has accumulated a large number of small errors that have not been reset. (Usually they are caused by usage of low-quality gasoline, presence of harmful impurities in fuel-air mixture, moisture on electric contacts, etc.).

If after performing the listed actions the Check Engine indicator is not extinguished, or is extinguished, but soon lights up again, it means that the error lies deeper. For its elimination it is necessary to carry out additional detailed diagnostics with more serious means.

Сheck engine warning light is on — what should I do next?

First of all, you need to find out how the car's behavior changed after the error occurred. This is done in order to determine whether it is possible to drive with a check engine light glowing on the panel or it is better to stop, so as not to aggravate the problem.

Car behaviorThe icon is on continuouslyCheck is blinking
Engine power and throttle response remained the sameYou can keep moving
No additional warning lights illuminated on the dashboard.
The engine became less quick, revs do not rise above a certain value (engine operation in emergency mode)You can keep movingThe movement CANNOT be continued.
The car has drastically changed its behavior:
  • RPMs are floating;
  • Engine vibration appeared;
  • Burning odor is heard;
  • Other changes.
The movement CANNOT be continued.
Along with the check engine icon, another indicator light came on:

Error analysis using the Torque app

A simpler method to read the error code and then decode it and find out the cause is to download a program for ECU communication and analysis (e.g. TORQUE) to your iOS OR Android smartphone. Or you can try to activate the self-diagnostic mode (this option is often available in Toyota, Opel, BMW). After counting the number of check flashes, check the technical documentation for the designation of such error code. For different cars there are different intervals between flashes and different codes by which they are interpreted.

If there are problems with spark plugs, injectors, as well as the activated check-engine indicator, there may be the following symptoms:

  • Poor engine traction;
  • high fuel consumption;
  • jerking when picking up speed or unstable engine operation;
  • «floating» engine rpm at idle.

The next step is to check pressure in the fuel system. You should use pressure gauge for this purpose. Standard pressure for the majority of non-tuned cars is 3 atm (kgf/cm2). However, check this information in the technical certificate of your car. If the pressure is much lower, the problem might be in a faulty gasoline pump or dirty injectors. If the pressure is low all the time — check the gasoline pump. If it is normal at first, but drops shortly after you start the engine — check the injectors. Also pay attention to the mesh in the gas tank.

It's also worth checking the insulation of the high-voltage wires. It's best to do this not visually, but with a tester turned on to ohmmeter mode. The minimum wire insulation value should not be less than 0.5 megohms. Otherwise, the wire must be replaced.

If the Check Engine light glows after turning the key, and after a few seconds goes out, it means that the system performs self-diagnostics, and there is no reason to worry.

How to get to the service station when the Check Engine light is on

When driving to the service station, try to drive gently. In particular:

  • do not exceed a speed of more than 60 km/h;
  • do not exceed engine speed over 2500 rpm;
  • turn off the air conditioner (heater), multimedia system and other unnecessary equipment that creates additional load on the engine;
  • avoid sudden starts and braking, and drive smoothly.

You may return to the normal driving mode only after diagnostics and elimination of detected errors.

Remember, do not panic if the Check Engine indicator appears. In most cases, the causes of its activation are not critical. However, it is necessary to perform the primary diagnostics consisting of 5 steps listed above. Also check if the car's behavior on the road has changed and if other indicators have lit up additionally. If minor faults are detected, they must be corrected. If Check Engine is not extinguished after that, then carry out additional diagnostics with the help of an electronic device. It will give you an error code, indicating the cause of the failure.

How much does it cost to fix a problem

The cost to fix each problem depends on the level of complexity:

FaultCost $
Lambda probe175
Tank cap replacement15
Catalytic converter200 — 600
Spark plugs20 per piece
Ignition coilsfrom 50 per piece
New mass air flow sensor120 — 150
EGR valve125
Batteryabout 100


  • What is the most common reason for check engine light?

    The most common reason for check engine light — is faulty oxygen sensor. Another widespread reasons: bad fuel, clogged injectors, problems with the spark plugs and low oil level.

  • Is it OK to drive with check engine light on?

    It's not necessary to repair your car at that time when the check engine just only started lighting. What you should do is to find out the main reason by carrying out diagnostics of all the main assemblies of the car.

  • What would a check engine light mean?

    Check engine light means that ECU has defined a problem in emission, fuel, exhaust or ignition systems.

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