What to do when your engine light comes on

Understanding the Engine Light

The engine light, also known as the "check engine light" or "malfunction indicator lamp" (MIL), is part of your vehicle’s onboard diagnostics system. It’s designed to alert you when the system detects an issue that could affect your car’s performance, emissions, or safety.

In modern vehicles, the engine light is connected to a wide array of sensors and components that monitor everything from engine performance to exhaust emissions. When something goes wrong, the light comes on to alert the driver that it’s time to investigate.

Assessing the Situation

The first thing to do when the engine light comes on is to assess the situation. If the light is steady, it generally indicates a non-urgent issue, though it still needs attention. If the light is flashing, it’s a sign of a more serious problem that requires immediate action.

A flashing engine light can indicate a misfire or a problem that could damage the catalytic converter if the vehicle continues to be driven. In this case, it’s important to pull over safely and turn off the engine as soon as possible.

Check for Other Warning Signs

In addition to the engine light, check your dashboard for other warning lights or gauges that might indicate a specific problem, such as low oil pressure or overheating. You should also listen for unusual noises or feel for any changes in the way the vehicle is handling. If you notice anything out of the ordinary, it might help pinpoint the issue.

Tighten the Fuel Cap

One of the most common reasons for the engine light to come on is a loose or faulty fuel cap. The fuel cap maintains pressure and prevents fuel vapours from escaping. A loose cap can cause a drop in pressure, triggering the engine light.

If the engine light comes on, especially after refuelling, the first thing to check is the fuel cap. Make sure it’s tightened properly. If it was loose, tightening it might resolve the issue. It can take a few drives for the light to reset after tightening the cap, so be patient and keep an eye on it.

Diagnosing the Problem

If the light remains on after checking the fuel cap, or if the issue appears to be more serious, it’s time to diagnose the problem further.

Use an OBD-2 Scanner

One of the most effective ways to diagnose the issue is by using an OBD-2 (On-Board Diagnostics) scanner. These devices can read the error codes generated by the vehicle’s computer, which can give you a more precise idea of what’s wrong.

Many auto parts stores offer free OBD-2 scanning, or you can purchase a scanner yourself. Once you have the error code, you can look it up to understand the problem better. However, while the code provides a clue, it doesn’t always tell the whole story, so further investigation might be necessary.

Consult the Owner’s Manual

Your vehicle’s owner’s manual is a valuable resource when it comes to understanding the engine light. It can help you interpret the light’s behaviour (steady or flashing) and provide guidance on what steps to take. The manual may also include information on common issues specific to your vehicle model that could trigger the engine light.

When to Seek Professional Help

There are times when your engine light indicates a more serious issue that will require help from a qualified mechanic.

Persistent Engine Light

If the engine light remains on after you’ve checked the fuel cap and run an OBD-2 scan, it’s time to seek professional help. Continuing to drive with the engine light on can lead to more severe damage, especially if the underlying issue is serious. A qualified mechanic can perform a more thorough diagnostic to identify and fix the problem.

Flashing Engine Light

As mentioned earlier, a flashing engine light indicates a serious issue that needs immediate attention. If your engine light is flashing, it’s best to stop driving the vehicle and have it towed to a mechanic. Driving with a flashing engine light could cause significant damage to the engine or catalytic converter, leading to expensive repairs.

Common Causes of the Engine Light

Understanding the common causes of an engine light can help you anticipate potential issues and respond appropriately when the light comes on.

Oxygen Sensor Failure

One of the most common reasons for an engine light is a faulty oxygen sensor. This sensor measures the amount of unburned oxygen in the exhaust system and helps the car’s computer adjust the air-fuel mixture. If the oxygen sensor fails, it can affect engine performance and emissions, leading to reduced fuel efficiency and higher emissions.

Catalytic Converter Issues

The catalytic converter is an essential part of your vehicle’s exhaust system, helping to reduce harmful emissions. If the converter fails, it can cause the engine light to come on. Catalytic converter issues can be serious, as a damaged converter can lead to decreased performance and increased emissions. In some cases, it may even cause the vehicle to fail an emissions test.

Mass Airflow Sensor Problems

The mass airflow sensor measures the amount of air entering the engine and helps determine the correct amount of fuel to inject. A malfunctioning mass airflow sensor can cause the engine light to come on, and it can lead to poor fuel economy, rough idling, and stalling.

Spark Plug or Ignition Coil Issues

Spark plugs and ignition coils are responsible for igniting the fuel-air mixture in the engine’s cylinders. If these components are worn or malfunctioning, it can cause the engine to misfire, which can trigger the engine light. Replacing spark plugs and ignition coils as part of regular maintenance can help prevent these issues.

Emission Control System Faults

Modern vehicles have complex emission control systems designed to reduce harmful pollutants. If there’s a fault in this system, such as a problem with the evaporative emissions control (EVAP) system, the engine light may come on. Issues with the EVAP system, for example, could be due to a loose or cracked fuel cap, faulty purge valve, or a leak in the system.

Preventive Measures

While the engine light can be a sign of various issues, many of them are preventable with regular maintenance and care.

Regular Maintenance

Staying on top of your vehicle’s regular maintenance schedule is the best way to prevent the engine light from coming on. This includes regular oil changes, air filter replacements, spark plug inspections, and checks of the fuel system. By keeping up with these tasks, you can prevent many common issues that trigger the engine light.

Use Quality Fuel

Poor quality fuel can cause deposits to build up in the engine, leading to problems with sensors and other components. Using high-quality fuel and adding a fuel system cleaner periodically can help keep your engine running smoothly and reduce the likelihood of the engine light coming on.

Monitor Fluid Levels

Low levels of essential fluids, such as engine oil and coolant, can cause the engine light to come on. Regularly checking and maintaining the proper fluid levels will help prevent issues that could trigger the light.

Dealing With an Engine Light Problem

The engine light is a valuable tool that alerts you to potential issues with your vehicle. When it comes on, it’s important to assess the situation, check for common issues like a loose fuel cap, and use an OBD2 scanner for further diagnostics.

We’ve got OBD2 scanners from Foxwell and Mechpro at Repco, as well as emergency fuel caps, and a wide variety of replacement parts for catalytic convertor or fuel system problems that you might need to deal with when the engine light rears its ugly head.

If the light persists or is flashing, and you’re not confident in your ability to fix major issues with your vehicle, seek professional help to avoid further damage. By staying on top of regular maintenance and understanding the common causes of the engine light, you can keep your vehicle running smoothly and prevent costly repairs.