Can a car throw codes without showing the check engine light?

Before answering this question, let me first explain that all vehicles come with a check engine light. It’s an onboard diagnostic system that tells you if something is wrong with the engine or the vehicle generally.

Something else you should know is fault/diagnostic trouble codes. These are codes that represent the particular problem your vehicle is having so that you can fix it accordingly.

So, back to the question: Can a car throw codes without showing the check engine light on the car’s dashboard?

The short answer is Yes. It happens mostly if the check engine light is bad due to one or another issue, which I’ll be explaining later.

For now, though, let’s try to understand the different types of diagnostic trouble codes available in the world of automobiles and where to see them.

Types of Vehicle Fault/DiagnosticTrouble Codes Available

Various types of OBD codes exist, starting with the letters P, B, C, or U each of which has a meaning. For example, P stands for powertrain, consisting of the engine, driveshaft, axles, differential, and transmission systems.

Similarly, B represents the car’s body, which is made up of several components. These include the main body, the windscreen, front, floor alongside roof panels, front and rear bumpers, front and rear doors, front and rear windows, etc.

Likewise, C is associated with the chassis, which similarly consists of various components such as the wheel carrier, wheel bearings, and wheels.

The rest are brakes, wheel suspensions((including anti-roll bar), and axle supports. Lastly, U is for network and wiring systems for the car, comprising the battery, starter, alternator, and so on.

Where Do I See My Trouble Codes?

You may wonder, where do I see the trouble codes registered by my car? Well, these five-digit codes display in the onboard diagnostics(OBD) code reader.

For starters, it’s an engine scanning tool designed to connect to the OBD system’s port beneath the dashboard on the driver’s side.

OBD code readers are sold separately from the car and there are plenty of them on the market some of which are available for as little as under $100.

If your check engine light comes on when you start the engine, you should connect your code reader to the car’s OBD system via the system’s port. Thereafter, you can use the code registered in your scanning tool as a starting point to further diagnose the car.

Why Would My Check Engine Light Fail?

It is a common situation for the check engine light to not show due to one reason or another. One of them is having a burned-out dashboard bulb associated with the check engine light system.

Notably, some cars, especially older ones, use ordinary light bulbs for their dashboards. Unfortunately, all ordinary light bulbs will eventually burn out, needing replacing. It’s just how they’re designed.

However, many modern cars, on the contrary, LED bulbs for their dashboards. These can last longer than normal bulbs and it’s less likely that your check engine light bulb will burn out before you change to another car, if it features an LED bulb.

What’s more, the check engine light may fail if there’s a bad electrical connection somewhere in the engine, preventing electricity from reaching it.

As you already know, a bulb cannot produce electricity without power. Meaning the bulb for your check engine light will not be able to light up if the electrical current is interrupted due to an issue.

Why Would a Car Not Throw a Code?

Every component or system of your car is prone to failure. That means your vehicle may be unable to throw a code if its internal self-diagnosis system, which is made up of sensors, and the ECM has become faulty or failed.

Will a Car Code Clear Itself?

The short answer is yes, depending on the severity of the issue that caused it to come on. In other words, it will clear itself if it was a minor issue that has stopped occurring.

Can You Have a Misfire Without a Check Engine Light?

Again, the short answer is yes. As said earlier, the check engine light is susceptible to failure. If you have a failed one, you can be sure it will not show(come on) if you have a misfire.

Can Spark Plugs Be Bad Without a Check Engine Light?

Likewise, the short answer is yes, for the same reason as above. As such, it’s essential to make sure that your check engine light is properly working at all times. You should test it each time you are performing your car maintenance routine.

How to Fix Code Showing Without a Check Engine Light?

If a code is showing without the check engine light, it could be that you have a faulty check engine light or scanning tool. Test the tool in another car with a known problem(s).

If it registers the expected code(s), you know that it’s working properly, meaning that there’s no need to replace it. What you should do here is to properly check the engine light as you could be having a faulty one.

On the other hand, if it fails to register the expected code(s), that can only mean that the tool is bad and therefore it needs replacing. Replacing it can help fix the problem.


The check engine light is an important diagnostic system that alerts you immediately if it detects a problem with your car. Using a reliable OBD code reader can help you identify what this particular problem is and fix it accordingly.

Unfortunately, the check engine light just like any other component or system of your car is prone to failure. If it fails, it won’t come on even if your car is misfiring or the spark plugs are bad.

Similarly, an OBD code reader can also become faulty, registering an error code, despite the engine light not showing that there is a problem with your car.

Whether it’s the check engine light or code reader that’s faulty, you want to fix that immediately to continue keeping your car in a great and safe condition.

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