What Can Cause a Check Engine Light to Come On?

Photo by Alexandru STAVRICĂ on Unsplash

You’re on the road enjoying your drive. It’s a beautiful day. No traffic, fantastic weather, even your favourite music is playing on the radio. BLISS. Then, out of the blue, an orange-red glow from the check engine light on your car dashboard catches your eye. Panic. Paranoia. Perfect day RUINED.

What are you going to do?

Here’s some expert tips on what can cause a check engine light to come on and how to fix it.

Your Gas Cap May Be Faulty

Most drivers aren’t aware of the fact that a faulty gas cap can cause the check engine light to come on. If the gas cap is loose, cracked, or faulty in any other way, it can cause fuel to evaporate. That triggers a faulty sensor and causes the check engine light to come on.

How to fix a faulty gas cap?

Pull over at the next safe stop and check that your gas cap is on and tight. In case the gas cap is cracked, have it replaced immediately.

If a faulty gas cap was the reason your engine light came on, then the engine light will go off once you keep driving for a few miles.

Diagnose Easily With GOFAR

If you prefer to cut the guesswork and avoid a potentially expensive trip to the mechanic – there is an easier – and cheaper – solution.

GOFAR is a self-diagnostic tool that alerts you when your car’s got a problem. GOFAR explains the issue in plain English so you now what you’re dealing with BEFORE you go to your mechanic.

How to monitor your car’s health every 2 seconds?

Install GOFAR in your car’s OBD2 diagnostic port – it takes just minutes and no technical knowledge is needed. Start getting real-time updates on any fault in your car in simple, plain English. No more tech jargon.

Check Engine Light – most cases

The good news is that it’s not always a disaster when the check engine light comes on. In most cases, when the check engine light is on but solid (not blinking) it may just be an alert that all is not well with your car.

How to fix the solid check engine light?

You can keep driving for a while until you can get to a mechanic. But don’t ignore it or forget to have your car checked as soon as convenient.

Related: Car Warning Lights Resource Centre

Check Engine Light – Emergency

Unlike the solid/steady check engine light, a blinking/flashing light means that there’s a serious problem with your car. In most cases, it’s the catalytic converter that has been damaged. Driving any further can be catastrophic.

How to fix a flashing check engine light?

Safely pull over as soon as possible. Shut the car engine off. Have your car towed to your trusted car diagnostic and repair facility – aka your mechanic.

Failed Ignition Coil

A faulty ignition coil hinders the efficient performance of the car engine. Faults such as misfires can trip the car’s computer and trigger the check engine light.

Also, when the computer detects a coil burn out or shorts it will trigger the check engine light to come on.

How to fix a failed Ignition Coil?

This is a serious problem that needs professional expertise. So, take your car to a certified mechanic as soon as possible.

Failed Fuel Injector

The fuel injector delivers fuel to the combustion chamber of your car’s engine at a controlled rate and in the right amounts. So, when the fuel injector fails, your car’s engine performance is greatly affected and can fail.

Any slight misfire may trigger on the check engine light. The misfire codes will vary depending on which fuel injectors are affected. And you can easily read them in plain English using GOFAR.

Other signs of a failed fuel injector include:

  • Abrupt loss of engine power: the fuel injector is clogged leading to an irregular supply of fuel.
  • Engine misfire due to the clogged fuel injector. This can cause the engine to overheat or pre-ignite the fuel mixture.
  • Persistent irregular fuel supply to the engine even when the engine idles. Instead of a smooth engine idle, it will be rough and irregular.
  • Reduced fuel efficiency due to leaking fuel or excessive fuel supply when the internal springs are damaged.

How to Fix Bad Fuel Injectors?

Since injectors (and engines) can be complicated and expensive to repair, it is advisable to have your car checked by a certified mechanic.

A faulty fuel injector can be repaired depending on the damage extent and age. Otherwise, you may need to buy a new one.

Bad or Failing Spark Plugs

Spark plugs are critical components of your vehicle. They transmit an electrical signal from the ignition coil to create a spark that ignites the combustion chamber.

Spark plugs are also responsible for the efficient burning of fuel. However, when faulty they can trigger the check engine light.

Other signs of failing spark plugs are:

  • Slow acceleration
  • Poor fuel economy
  • Engine is misfiring
  • Difficulty in starting your car

How to fix failing/bad spark plugs?

Spark plugs require regular service and maintenance. Therefore, have your mechanic check them out and replace them if faulty so that your car engine remains strong and reliable.

Luckily, once you replace the spark plugs, you can drive for many years or miles before replacing them.

You may also need to check your spark plug wires. Read on…

Defective Spark Plug Wires

Spark plug wires, also known as ignition cables, should also be checked alongside the spark plugs. Over time the spark plugs do age due to exposure to extreme hot or cold temperatures.

Also, engine chemicals such as coolants, grease, and oil may cause damage to the spark plugs over time.

Such damage will often cause the check engine light to come on. Other signs of failing spark plug wires include:

  • The decrease in engine power and acceleration
  • Engine Surging
  • Reduced fuel efficiency
  • Rough engine idle
  • Visible damage on the wires

How to fix defective spark plug wires?

Check the spark plug wires for any signs of melting or cracking. If damaged, have them replaced a soon as possible.

Failing Engine Control Module

The engine computer is commonly referred to as the:

  • Engine Control Module (ECM), or
  • Engine Control Unit (ECU), or
  • Powertrain Control Module (PCM)

The ECM controls all the essential functions of your vehicle including engine performance and the drivability functions.

When the ECM is failing, it will trigger the check engine light to alert you of a potential issue with its sensor or circuits.

Other possible signs of a faulty ECM are:

  • Engine stalling or misfiring
  • Engine performance issue such as throwing off timing and the engine fuel settings
  • Car not starting or difficult to start

How to fix a failing Engine Control Module?

The ECM plays a major role in the performance of your car engine. Any issue with it can largely affect the overall performance of your car.

Therefore, have your vehicle inspected by a certified technician because the ECM is quite sophisticated and complicated.

Engine Valves Failure

Did you know that your car’s engine valves normally open and close up to 2,500 times every minute? That’s an enormous amount of stress on these components.

So, when damaged these vital components of the car engine can trigger the check engine light. The two most common causes of damaged valves are:

Bent or Broken Engine Valves

The engine valves bend or break due to contact with the pistons caused by incorrect engine synchronization. It often happens when a timing/chain belt breaks or a new one is incorrectly fitted.

How to fix a bent or broken engine valves?

If you suspect a bent or broken engine valve, switch off the engine and do not attempt to start it because you may cause costly damage to the cylinder head, pistons, and cylinder bores.

Your timing belt doesn’t last forever. You need to replace it according to your manufacturer’s service guidelines.

Replacing your timing belt is not only cheap but is also an insurance policy against costly engine damage.

Burnt Engine Valves

When combustion gases escape between the valve and the valve seat, it means they are not sealing properly. As the combustion gases are forced through the valve, they slowly start to burn the edges of the valve.

If not rectified over time, the engine valves get worse and even cause damage to the intake valves. Therefore, the burnt engine valves may trigger the check engine light to come on.

The other signs of burnt engine valves to look out for are:

  • Reduced car performance
  • Reduced fuel efficiency
  • Rough engine idle
  • Reduced power
  • Engine backfiring
  • Engine misfire

How to fix burnt engine valves?

If you continue driving your car, the burnt valve will cause more damage that will be costly to repair in the long run. So, get your car checked by a certified mechanic as soon as possible.


In truth when the check light engine comes on and you have no idea what to do, it can be scary. Luckily, you now have some handy tips. Use them.

Better still, you can cut the guesswork and elimination method by getting yourself a GOFAR today.

Get alerts on all your car’s problems in plain English and driver smarter.

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