Blog Car Care Advice Top 8 Causes for a Lexus Check Engine Light (+How to Fix)
Car Care Advice

Top 8 Causes for a Lexus Check Engine Light (+How to Fix)

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The Lexus check engine light is often a source of both concern and curiosity for drivers. 

It’s clear something is wrong, but figuring out what’s causing the issue can be tricky as there are a lot of potential causes, from a loose gas cap to a defective catalytic converter

We’ll go through the common causes of the Lexus check engine light, what to do when it illuminates, and more.

This Article Contains: 

Let’s get to it.

What Causes the Lexus Check Engine Light to Activate?

Whether you’re behind the wheel of the latest Lexus RX350 or any other model, here are common reasons for the check engine light activating in a Lexus vehicle: 

1. Loose Gas Cap

As silly as it sounds, this is quite a common reason for an illuminated warning light. Double-check that the gas cap is secured tightly and there are no signs of damage. A damaged or loose gas cap allows fuel vapors to escape, reducing your fuel economy and activating the check engine light.

2. Faulty Spark Plugs or Spark Plug Wires

The spark plugs sit in the cylinder head and ignite the air-fuel mixture within the cylinder. As the ignition coil creates the spark, the spark plug wires carry it to the spark plugs. If your spark plugs or spark plug wires are acting up, it can lead to engine misfires, reduced engine performance, and an illuminated check engine light.

3. Defective Catalytic Converter

The catalytic converter minimizes harmful emissions by converting harmful gasses like nitrogen oxide and carbon monoxide into carbon dioxide and steam.

With time, carbon deposits can build up and block the catalytic converter. If this happens, the check engine light will activate, and you may notice increased emissions, poor fuel efficiency, and reduced engine performance from your vehicle.

4. Busted Mass Air Flow Sensor (MAF)

The mass airflow sensor in your Lexus vehicle measures the amount of air flowing into the engine to help determine the correct amount of fuel needed.

If dirt and debris get into the sensor, it can contaminate the parts and cause an MAF sensor failure. Aside from illuminating the check engine light, other common symptoms of an MAF sensor failure are difficulty starting, rough idling, and black smoke from the exhaust.

5. Vacuum Leak

Your Lexus has a vacuum system that performs essential functions, like reducing emissions and boosting the braking ability. With time, the vacuum hoses can become dry and crack. If your check engine light activates and you notice a higher-than-usual idle RPM or random spikes, a vacuum leak may be behind it.

6. Bad Ignition Coil

The ignition coil converts low-voltage electrical currents from the battery into a high-voltage current for the spark plug. 

There are many potential reasons for an ignition coil to fail, including heat and vibration. If the ignition coil starts acting up, you may notice misfires, stalling, and reduced performance, resulting in an illuminated check engine light. 

7. Faulty Oxygen Sensor (O2 Sensor)

The oxygen sensor, or O2 sensor, monitors the amount of oxygen in the exhaust gas. This helps your car’s computer to adjust the air-fuel mix. If a bad oxygen sensor is responsible for your Lexus check engine light, you may notice a drop in fuel economy, reduced engine performance, and increased emissions.

8. Dirty Air Filter

Your air filter’s primary responsibility is to filter the air entering the engine. Although less common, if the air filter is blocked, it may trigger the check engine light with a P0172 code, signifying the engine is running rich.

So what can you do when your Lexus check engine light illuminates? 
Read on to find out.

What to Do if Your Lexus Check Engine Light Turns On 

Generally, the check engine light illuminates and remains lit, indicating a faulty part. But that can vary depending on the seriousness of the problem.
Let’s see what you should do on a case-by-case basis.

A. Illuminates Under Certain Conditions 

If the check engine light isn’t always on, it often means a part is about to fail. When this happens, the best thing to do is pay attention to how your Lexus car feels while driving and note any changes.

A good idea is to check if another warning light is active besides the engine light. For example, Lexus owners may also see the VSC light illuminate, which may signify an issue with your Vehicle Stability Control. 

Whether the VSC light is active or not, you should make a booking with a qualified mechanic

B. Light is Constantly On 

If the light is constantly on, your car lets you know it has detected a fault with one of the components. When this happens, you should stop driving as soon as possible and have a trained mechanic perform a check engine light diagnosis.

C. Light is Flashing 

A red or flashing check engine light often indicates unburned fuel is entering the exhaust system. This can lead to engine misfires and put additional strain on crucial engine components, such as the catalytic converter. If you see a flashing check engine light while driving, pull over as soon as it’s safe and have your car towed or call a mobile mechanic.

Now that we know what to do when the check engine light activates, let’s determine if it will reset.

Will the Check Engine Light Reset Itself?

Yes, Lexus owners should see the check engine light reset automatically once a mechanic has fixed the problem. In some cases, you may need to wait a few cycles. A cycle generally involves turning the vehicle on and leaving it running for some time before turning it off.

However, if you’ve fixed the problem and that yellow light is still active, you can use an OBD II scanner to discover more about the check engine light codes and reset the stored code. If you don’t have an OBD II scanner, you can try disconnecting the negative terminal on the car battery.

Note: The check engine light will reactivate if the issue remains. In this case, having a qualified mechanic diagnose the problem is best.

Wondering how much a Lexus check engine light diagnosis could cost?
We’ll answer that next.

How Much Does it Cost to Get a Lexus Check Engine Light Diagnosed?

Diagnosing a Lexus check engine light should cost between $91 and $119. However, the actual cost of the repairs will depend on the part that needs replacing.

Wrapping Up

Whether you’re driving the new Lexus RX350 or another model, never ignore that little red or yellow light. This can lead to a costly engine repair for your Lexus car. For any problem, be it a faulty gas cap or a worn mass airflow sensor, your best bet is to have a qualified mechanic take a look.

Since you shouldn’t drive with a check engine light, why not have a mobile mechanic from AutoNation Mobile Service fix the issue in your driveway? 
We service new vehicles and pre-owned vehicles, provide easy online booking, and offer a 12-month | 12,000-mile warranty on all repairs.

Contact us for a quick check engine light diagnosis or any other engine repair.