Reasons your Check Engine Light is On

If you find yourself in this situation light pops up in your dashboard. It looks like the outline of a car’s engine, and the words “check” or “check engine” might appear next to it. It’s the check engine light. While it’s often assumed that the check engine light (CEL) is an indication of a major mechanical issue, this isn’t always the case. In fact, according to many professional mechanics, a warning light can be caused by a minor electrical glitch.

A check engine light is triggered when your vehicle’s onboard computer or ECU detects an error coming from one of the multiple sensors on your car. When this happens, the ECU creates and stores an OBD-II diagnostic trouble code, which then illuminates the CEL.

Here are the reasons the CEL can light-up, and the best ways to resolve these issues.

One Sensor has a loose Electrical connection or is damaged

Believe it or not, the most common reason the CEL will light up is due to a poor electrical connection from the ECU to the sensor. When the electrical harness is loose, frayed, damaged, or exposed, it can send a signal to the ECU and mimic a mechanical problem. It’s also common for sensors to wear out over an extended period of time.

An engine will keep running even if an O2 sensor needs to be replaced, but it will burn more fuel than usual. In the long run, a bad O2 sensor can damage components like spark plugs and the catalytic converter. It may also cause a car to fail an emissions test.

What can be done to fix this? In most cases, a professional mechanic will simply replace the sensor and the electrical harness to resolve this type of problem.

Loose or Damaged Fuel Cap

Today’s modern cars are very carefully monitored for fuel economy and emissions. If the gas cap is either left off, damaged, or does not maintain a solid seal, it will create less pressure inside the fuel cell. This tells the sensor there is a damaged or loose gas cap and can cause acceleration problems and/or poor gas mileage. Additional signs of a broken fuel cap include:

  • Cap does not tighten or lock properly.
  • Car smells like fuel

What can be done to fix this problem? Most of the time, replacing the gas cap can solve the problem. However, you’ll have to contact a professional mechanic to complete a check engine light inspection in order to remove the code and reset the warning light.

Catalytic converted is clogged

The catalytic converter is designed to filter exhaust before it heads out the tailpipe. It converts harmful carbon monoxide into carbon dioxide. Like any other filter, the catalytic converter can wear out or become clogged with too much debris to be effective. When this happens, it will create an error code and trigger the CEL. A clogged catalytic converter can cause poor fuel mileage, engine misfiring, and even lead to internal engine damage if not replaced. More signs of a failing catalytic converter are:

  • Poor fuel efficiency
  • Little acceleration when pressing on the gas pedal
  • The vehicle refuses to start

How to fix this issue? Replace the catalytic converter. Performing regular maintenance (such as oil changes) on time is key to keeping your car’s catalytic converter in working order.

Spark Plug/Ignition coil issues

As its name implies, a spark plug wire transfers electricity from the coil to the spark plug. Without it, the fuel and air mixture in the cylinders wouldn’t ignite. A malfunctioning coil will and worn or fouled plugs almost certainly trigger the check engine light, but remember, if your car burns diesel, you have neither ignition coils nor spark plugs.

How to fix this issue? Changing your own spark plugs is also easier than it sounds.

Mass Airflow Sensor is damaged

The mass airflow sensor or MAF is responsible for carefully mixing the right ratio of air to fuel, maintaining a clean and efficient burn inside the combustion chamber of your engine. If the MAF is damaged, the MAF sensor will send a signal to the ECU to let you know this needs to be replaced or cleaned.

Other symptoms of a failing air flow sensor include:

  • Engine stalls shortly after starting
  • Hesitating engine with a heavy load and/or during acceleration
  • Hiccuping engine

How to fix a mass air flow sensor issue? This is one of those problems that should be inspected by a professional mechanic first. They can determine whether the light is caused by a damaged MAF sensor or it simply needs to be cleaned.

Engine has oil lubrication issues.

Your engine needs oil to keep all those moving parts cool as it revs up. Sometimes, dirty oil, engine sludge, or a damaged oil pump can cause oil pressure to reduce or increase higher than it should. When this happens, the oil pressure sensor will tell your ECU and illuminate the CEL. This is one of those situations that should be taken very seriously, as an engine not receiving the proper lubrication can overheat quickly and cause internal engine damage. It can also be possible that this sensor is damaged and sending false data.

The warning could indicate something simple and harmless – or something serious that could cause further damage to your vehicle. Pay close attention to your vehicle’s performance.  If you don’t notice anything unusual, it’s likely safe to continue driving your vehicle to a safe location, even though the check engine light is on. However, proceed with caution and be sure to get it diagnosed and repaired right away to prevent further damage.

Auto King Mobile Mechanics can come to you for any vehicle repair, service, and inspection needs. Book or Call for a free quote!