Today’s vehicles use more advanced technology than any of their predecessors. That can be both good and bad. 

It’s nice being able to rely on sensors to help you drive. Imagine a road trip without cruise control. Or backing up without the tiny cameras to alert you to potential problems. 

Yet when you turn your car on, and a dashboard light refuses to turn off, you know you have a problem. 

Is it a significant issue? Should you act immediately? Or can you wait until a more convenient time? 

One of the most troubling is a check engine light. Engine failure can be a costly repair, one you should avoid at all costs.

But what do those codes mean? Is it possible to diagnose check engine light codes on your own? 

What is a check engine light?

The check engine light is a warning light on a vehicle’s dashboard that illuminates when the vehicle’s onboard diagnostic system (OBD) detects a problem or potential issue with the engine or emissions system.

Modern vehicles have an OBD system that continuously monitors various components and systems, such as the engine, fuel system, exhaust system, ignition system, and emissions controls. When the OBD system detects a problem, it generates a fault code and triggers the check engine light to alert the driver that an issue needs attention.

The check engine light can be triggered by a wide range of problems, ranging from minor issues, such as a loose gas cap, to more serious engine or emissions-related malfunctions. The purpose of the light is to prompt the driver to take action and have the vehicle diagnosed and repaired to prevent potential damage, reduce emissions, and ensure proper functioning of the vehicle.

When the check engine light comes on, it is advisable to have the vehicle inspected by a qualified mechanic or use an OBD scanner to retrieve the specific fault code(s) stored in the vehicle’s computer system. These codes can provide valuable information about the nature of the problem and help diagnose the issue more accurately.

Is there a way to find these fault codes on your own? 

Seeing a check engine light and wondering what is wrong with your vehicle can be frustrating. Is it serious? Is it not? How can you tell? 

There are ways for you to determine the potential problem on your own. It all depends on what car you own and what tools you have at your disposal. 

OBD-II Scanner – OBD-II scanners are available for purchase, or you may find them for rent at automotive parts stores. These scanners can be connected to the OBD-II port, which is usually located under the dashboard on the vehicle’s driver’s side. Once connected, the scanner can communicate with the vehicle’s computer system to retrieve the fault codes. The scanner will display the codes on its screen, allowing you to identify the specific issues.

Smartphone Apps – There are several smartphone apps available that can turn your phone into an OBD-II scanner. You’ll need an OBD-II Bluetooth or Wi-Fi adapter that plugs into the OBD-II port of your vehicle. The app connects to the adapter and retrieves the fault codes, displaying them on your phone’s screen.

Built-in Diagnostic Functions – Some vehicles have built-in diagnostic functions that allow you to retrieve fault codes without needing an external scanner. The process varies depending on the make and model of your vehicle. Consult your vehicle’s owner’s manual or search online for instructions specific to your vehicle.

It’s important to note that while these methods allow you to retrieve the fault codes, they do not provide detailed analysis or diagnosis of the problem. Once you have the fault codes, it’s recommended to research or consult a qualified mechanic to interpret the codes and determine the appropriate course of action for repairing the issue. This may give you a better picture of the potential problem and what it will take to fix it, but it’s not a complete diagnosis. A professional is your best course of action to ensure the issue is resolved correctly the first time. 

What are the most common codes and reasons a check engine light turns on?

Specific fault codes can vary depending on the vehicle’s make, model, and year. However, some standard fault codes occur more frequently. Here are a few examples of common fault codes and their potential causes:

P0300 – Random/Multiple Cylinder Misfire

This code indicates that the engine is misfiring in multiple cylinders. Possible causes include spark plug or ignition coil issues, fuel delivery problems, vacuum leaks, or a malfunctioning mass airflow sensor.

P0171/P0174 – System Too Lean

These codes indicate that the engine is running too lean (too much air and not enough fuel) on either bank 1 (P0171) or bank 2 (P0174) of the engine. Potential causes include a vacuum leak, faulty oxygen sensor, clogged fuel injectors, or a malfunctioning fuel pressure regulator.

P0420/P0430 – Catalyst System Efficiency Below Threshold

These codes indicate that the catalytic converter is not operating at its expected efficiency level. Causes include a failing catalytic converter, oxygen sensor issues, engine misfires, or exhaust leaks.

P0442 – Evaporative Emission Control System Leak Detected (Small Leak)

This code indicates a small leak in the vehicle’s evaporative emission control system, which helps control fuel vapor release into the atmosphere. A loose or faulty gas cap is a common cause, but it can also be due to leaks in hoses, valves, or charcoal canisters.

P0401 – Exhaust Gas Recirculation (EGR) Flow Insufficient

This code indicates that the EGR system is not functioning correctly, resulting in insufficient exhaust gas recirculation. Causes include a clogged EGR valve, faulty EGR solenoid, or carbon buildup in the EGR passages.

These are just a few examples, and there are many other potential fault codes and causes for a check engine light to illuminate. When the check engine light comes on, it’s best to consult a qualified mechanic or vehicle service manual for a proper diagnosis and repair.

How can we help you correctly diagnose and care for your vehicle?