Rosied55

I have an NX 350 that is only 6 mos old with 1700 miles on it and the engine light came on. Anyone have this issue on a new car?

Droid13

There are probably a thousand different reasons the money light, er, I mean the check engine light would turn on. First step is (find someone to) read the code(s) triggering the warning.

gamma742

At 6 mo and 1700 miles. I'd make an appointment and let Lexus sort it out. They'll usually give you a loaner and a free cup of designer coffee maybe some snacks.

Randyp1234

Yes - there's no reason to do any kind of do-it-yourself things when it's darn near right off the lot and under warranty, unless you just can't get in contact with them.

AM123

Just to reiterate what fellow NXers have said: since your car is still pretty new, the best move is to reach out to the dealer and let them do their “thing”. Plus, take advantage of the trip and try their coffee—French vanilla comes highly recommended! lol.

midcow3

You, didn't by chance have a 12 volt battery failure and install a replacement battery or disconnect your current battery. Sometimes this causes a temporary false check engine light which goes away on its own after awhile. You didn't mention it so this is probably not the cause. But, what were the exact event that preceded the check engine light and maybe we have an easy answer.

YMMV,
MidCow3

Datanator

A fuel filler cap not properly tightened will cause this as well.

midcow3

most common causes

Home > Check Engine Light

The 13 Most Common Reasons For A Check Engine Light | How To Diagnose Them

The check engine light in your car is vital to help uncover problems. But there’s a lot more to understand than just a dashboard warning. This detailed article reviews the most common causes for a check engine light coming on, how to identify troubles, and what the repairs will cost you.

• David Goldberg
• April 12, 2023

TABLE OF CONTENTS

• 1. Loose Gas Cap
• 2. Spark Plug & Plug Wire Issues
• 3. Low Oil & Low Oil Pressure Problems
• 4. O2 Sensor
• 5. Catalytic Converter
• 6. Mass Airflow Sensor
• 7. Overheating
• 8. Transmission
• 9. Battery
• 10. Vacuum Leak
• 11. Exhaust Gas Recirculation Valve Failure
• 12. Your Vehicles Check Engine Light Is On For No Reason Or Malfunctioning (& other common reasons for DTCs)
• 13. Failing Aftermarket Alarm
• Frequently Asked Questions: The 13 Most Common reasons For A Check Engine Light

Diagnose and clear your check engine light!

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1. Loose Gas Cap

[img]data:image/svg+xml;base64,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[/img]If you see a check engine light after getting gas, the likely culprit is a loose or faulty gas cap. This is actually one of the most common reasons why a check engine light is triggered. Modern vehicles require a tight cap to prevent harmful fuel vapors from escaping into the environment. At the same time, a secure cap stops dirt and debris from entering the fuel tank.

Can I Drive?

Driving with a loose or broken gas cap is fine, but attend to the problem as soon as possible.

What DTC Codes?

Symptoms: Check Engine Light Is On & Maybe A “Gas Cap” Dashboard Message

What Could It Cost To Fix the Problem?

How To Reset Check Engine Light?

How Long Until the Check Engine Light Resets After a Loose Gas Cap?

2. Spark Plug & Plug Wire Issues

[img]data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20width='2560'%20height='1707'%20viewBox='0%200%202560%201707'%3E%3C/svg%3E[/img]

Can spark plugs cause a check engine light to come on? Yes, Spark plugs wear out over time and can trigger a check engine light if they cause a misfire.

Can I Drive?

While continuing to drive with a bad spark plug or spark plug wire won’t cause immediate damage to the car, poor acceleration or a stuttering engine can present a safety hazard. So, address the issue as soon as possible.

What DTC Codes?

Symptoms: Typically Only The Check Engine Light Is On

What Could It Cost To Fix the Problem?

Will a Broken Spark Plug Wire Turn on a Check Engine Light?

3. Low Oil & Low Oil Pressure Problems

Can an oil change cause the check engine light to come on? Seeing a check engine light after an oil change or noticing a check engine light after adding oil isn’t uncommon and usually involves a simple fix. Start with ensuring that the oil dipstick and oil fill cap are properly seated; this is also a good time to double-check the oil is at the correct level. Although rare, sometimes the oil drain plug can become loose or fall out after an oil change, allowing the oil to empty. In this situation, stop everything and contact the repair shop where the work was done.

Having low oil pressure and a check engine light on after an oil change often just means the sensor needs time to reset. Other times the sensor has gone bad. If your check engine light is still on after replacing the oil pressure sensor, take a trip back to the repair shop.

Does the check engine light come on for an oil change, or can low oil cause the check engine light to come on? Generally, no. Most cars have a separate indicator for oil-related issues, like a low-oil warning or low oil pressure. Further, some vehicles have oil change

Can I Drive?

Unless you’re certain your car is just burning oil (not a leak or a bad oil pump etc.), pull over (where it’s safe) and turn the car off. Call a tow truck, and don’t take any chances, you can destroy your engine by driving with low oil or low oil pressure regardless of the cause.

What DTC Codes?

Symptoms: Oil Warning Light And Check Engine Light Are On

What Could It Cost To Fix the Problem?

4. O2 Sensor

[img]data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20width='512'%20height='341'%20viewBox='0%200%20512%20341'%3E%3C/svg%3E[/img]

An O2 sensor check engine light appearing is nothing unusual, particularly on older cars with a failing pollution control system. A check engine light being triggered by an oxygen sensor indicates the O2 sensor can no longer properly monitor engine functionality like the fuel-to-oxygen ratio, air temperature, and other factors needed to adjust emission levels. It’s also not uncommon for a car to have a check engine light that goes on and off for the O2 sensor.

Can I Drive?

Your car is drivable with this issue, but don’t hold off too long on repairs. Driving with a faulty O2 sensor could lead to a damaged catalytic converter. Turning what could have been $200 – $500 O2 sensor replacement into a $2000 catalytic converter replacement.

What DTC Codes?

Symptoms:

What Could It Cost To Fix the Problem?

I changed my O2 sensor and the check engine light is still on

5. Catalytic Converter

Seeing a check engine light for a catalytic converter malfunctioning is a common occurrence, particularly with an older car. Through an elaborate filtering system, the catalytic converter transforms harmful elements (hydrocarbons, nitrogen oxide, and carbon monoxide) from exhaust fumes into friendlier substances (water vapor, nitrogen, and carbon dioxide)

Can I Drive?

You can operate a car with a failing catalytic converter but have the problem examined as soon as possible to avoid further engine damage.

What DTC Codes?

Symptoms: Catalytic Converter Warning Light Or Check Engine Light Is On

What Could It Cost To Fix the Problem?

Will removing the catalytic converter cause the check engine light to come on?

Will a high-flow cat cause a check engine light?

How to bypass the catalytic converter check engine light - A common but, typically, bad idea

6. Mass Airflow Sensor

[img]data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20width='2560'%20height='1707'%20viewBox='0%200%202560%201707'%3E%3C/svg%3E[/img]

The mass air flow sensor (MAF) measures the airflow entering the engine and is a vital component in a modern fuel injection system. Having a malfunctioning or dirty mass air flow sensor (or a dirty air filter) can result in an improper air-to-fuel ratio being fed to the engine’s combustion chamber and may even cause a misfire if the MAF sensor malfunction is severe enough.

Can I Drive?

It’s acceptable to drive with a MAF sensor problem. However, remember that poor acceleration and other engine performance issues can create a dangerous situation (like during highway merging or turning at an intersection).

What DTC Codes?

Symptoms: Typically, Only The Check Engine Light Is On

What Could It Cost To Fix the Problem?

What if there’s a check engine light after cleaning the MAF sensor?

Can your mass airflow sensor be bad without a check engine light?

What if I replace the mass air flow sensor and the check engine light is still on?

Does unplugging your mass airflow sensor and reconnecting it make your check engine light go on?

I have a power ground and signal to the mass airflow sensor, so why is my check engine light still on?

7. Overheating

Among the most severe problems a vehicle may encounter is high engine temperature. So, noticing a car overheating with a check engine light requires immediate action. Ignoring this condition can lead to catastrophic engine failure. So, at the first sign of overheating, pull over (where it’s safe to do so) and turn the car off.

Importantly, don’t ever operate a car with an overheated engine. Call a tow truck, or if the repair shop isn’t too far away, let the engine cool down and drive to the mechanic.

Topping off coolant or water if you have a leak can help you drive just a little further if you are stuck. But, never pour water into a hot engine, let it cool down first. Also, keep in mind that pure water in your engine and radiator in freezing temperatures can result in frozen water in your cooling system. Freezing water can expand as it turns into ice and cause serious damage to your car. If you add water to get home or to a shop, make sure you drain it before the engine gets cold.

Can I Drive?

Do not operate a car with an overheated engine. Call a tow truck, or if the repair shop isn’t too far away, let the engine cool down and drive to the mechanic.

Topping off coolant or water if you have a leak can help you drive just a little further if you are stuck. But, never pour water into a hot engine, let it cool down first. Also, keep in mind that pure water in your engine and radiator in freezing temperatures can result in frozen water in your cooling system. Freezing water can expand as it turns into ice and cause serious damage to your car. If you add water to get home or to a shop, make sure you or the mechanic drains it before the engine gets cold.

What DTC Codes?

Symptoms: Engine Temperature Warning Light And Check Engine Light Are On

What Could It Cost To Fix the Problem?

Can low coolant cause a check engine light to come on?

8. Transmission

[img]data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20width='2560'%20height='1707'%20viewBox='0%200%202560%201707'%3E%3C/svg%3E[/img]

Besides engine problems, few car repairs are as serious and urgent as solving transmission issues. Today’s gearboxes are intricate assemblies designed to balance fuel economy and performance, and this complexity can make repairs extremely expensive. Fortunately, every transmission problem doesn’t involve hundreds or thousands of dollars, but getting any issues looked at right away is vital.

Can I Drive?

Because a weakened transmission can quickly accelerate (pun intended) into a destroyed transmission, it’s best not to drive a car with a finicky gearbox.

What DTC Codes?

Symptoms: Transmission Light And Check Engine Light Are On

What Could It Cost To Fix the Problem?

Will a check engine light come on for the transmission?

Can low transmission fluid cause a check engine light to come on?

What if I see a check engine light after a transmission fluid change?

9. Battery

Own a car long enough, and you’ll need to change the battery; they only last for three to five years. Often, a dead battery only becomes noticeable once the car won’t start and the check engine and(or) battery light are on.

Can I Drive?

You won’t harm a car by driving with a dying battery, but installing a new battery can easily overcome the risk of getting stranded.

What DTC Codes?

Symptoms: Battery Light On In The Car And The Check Engine Light Is On

What Could It Cost To Fix the Problem?

What does it mean when the check engine light and the battery light are on?

Can a bad battery cause a check engine light to come on?

What if there’s a check engine light on after a battery change?

How to reset the check engine light after a battery change

10. Vacuum Leak

[img]data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20width='512'%20height='385'%20viewBox='0%200%20512%20385'%3E%3C/svg%3E[/img]

A car requires an ideal balance of gas and air to maximize performance and economy; any change in this proportion will affect how a vehicle operates. We’ve covered how the MAF and O2 sensors impact things, but maintaining a vacuum within the fuel system is equally important.

Can I Drive?

Driving with a vacuum leak isn’t a significant issue, but get things fixed when it’s possible to do so.

What DTC Codes?

Symptoms: Usually, Only The Check Engine Light Is On

What Could It Cost To Fix the Problem?

Will a vacuum leak cause a check engine light?

11. Exhaust Gas Recirculation Valve Failure

The exhaust gas recirculation (EGR) valve regulates exhaust gases to lower nitrogen oxide emissions, improve engine efficiency, and increase fuel economy. An EGR valve can go bad or just get clogged with carbon buildup over time.

Can I Drive?

Short-term driving with a bad EGR valve is OK, but ignoring the problem can lead to replacing the catalytic converter. A bad EGR, O2 sensor or catalytic converter can be driven on but, you should get the repair as soon as possible to avoid increasing repair costs.

What DTC Codes?

Symptoms: Check Emission System Lights And The Check Engine Light Are On

What Could It Cost To Fix the Problem?

12. Your Vehicles Check Engine Light Is On For No Reason Or Malfunctioning (& other common reasons for DTCs)

[img]data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20width='2560'%20height='2560'%20viewBox='0%200%202560%202560'%3E%3C/svg%3E[/img]

While car owners would like to think their cars are rolling examples of computerized perfection, the truth is that technology isn’t perfect. Asking if a check engine light can come on for no reason is a valid question.

Suspicious check engine lights can happen for several reasons. Some older cars are engineered for odometer triggering that serves as a maintenance reminder at specific mileage intervals. False triggering or other triggering can come from a computer system that believes a component isn’t operating correctly – a loose wire or connector, an electrical issue, and hundreds of other triggering possibilities exist. Fuel with higher amounts of methanol/ethanol can also trigger a check engine light so make sure you are filling your car with gasoline that has the manufacturers recommended octane rating.

Can I Drive?

Is there any unusual sound, smell, or vibration? Does something not look or feel right? If something isn’t normal about your car (besides the CEL), calling a tow truck is usually wise. Spending time and money on a tow truck is far better than making matters worse by continuing to drive and potentially increasing the cost of your repair tenfold.

What DTC Codes?

Symptoms: Other Warning Lights And The Check Engine Light Are On

What Could It Cost To Fix the Problem?

Why is my vehicle's engine light on, but nothing seems wrong?

13. Failing Aftermarket Alarm

High-quality aftermarket alarms are engineered to be installed without disrupting normal vehicle operations. However, improper installations or cheap systems are another story. Tying in an alarm to the wrong part of the electrical system can cause a CEL to come on. And a sub-par alarm may not be designed to work correctly with your car.

Can I Drive?

Driving with a fussy aftermarket alarm system won’t damage the car (but may drain the battery). However, you could have to deal with problems locking and unlocking the doors, trouble starting the engine, and an alarm that goes off when there’s no security issue. It’s also best to get this fixed so you don’t develop the habit of ignoring your check engine light should a more serious issue come up.

What DTC Codes?

Symptoms: Other Warning Lights And The Check Engine Light Are On

What Could It Cost To Fix the Problem?

Can a car alarm cause a check engine light?

FIXD has scanned thousands of cars and created a solution that explains vehicle troubles in plain English. With the FIXD Sensor and free app, looking up DTC codes is unnecessary. FIXD quickly tells you what your check engine light means and helps you save money by avoiding unnecessary repairs when you visit the auto repair shop or dealership. The app can also help you avoid check engine related problems in the first place by alerting you when your car needs important maintenance, such as oil changes. Click here to learn more and get FIXD for only $19.99 (regular price $59)!

Frequently Asked Questions: The 13 Most Common reasons For A Check Engine Light

[img]data:image/svg+xml,%3Csvg%20xmlns='http://www.w3.org/2000/svg'%20width='2560'%20height='1706'%20viewBox='0%200%202560%201706'%3E%3C/svg%3E[/img]

How to Read & Diagnose Your Check Engine Light With & Without A Scanner

Knowing how to read a check engine light is an essential part of car ownership. We think the easiest way to understand what’s going on with your engine is to use the FIXD Sensor and free app, which will scan the car and provide the DTC code in a simple, plain English answer. An OBD II scanner is another option, but you’ll still need to look up the error code. Alternatively, the owner’s manual for the car may provide information about the check engine light too.

"Check Engine" Light: Flashing vs. Static - What's The Difference?

What Do You Do When Your "Check Engine" Light Comes On?

Where Can You Get Your Check Engine Light It Checked For Free?

How Do You Reset A Check Engine Light?

Can Bad Gas Cause A Check Engine Light?

Can I Ignore My ‘Check Engine’ Light?

Will The Check Engine Light Go Off By Itself?

Does The Check Engine Light Turn Off Automatically After Repair?

Can Cold Weather Cause A Check Engine Light?

Can An Exhaust Leak Cause A Check Engine Light?

My Check Engine Light Came On After Driving Through Water; What Now?

Clear Your Check Engine Light In Seconds

The FIXD Sensor and free app tells you why your check engine light is on in easy-to-understand terms and lets you clear it with the touch of a button.
LEARN MORE AND SAVE 67%We’re here to help you simplify car care and save, so this post may contain affiliate links to help you do just that. If you click on a link and take action, we may earn a commission. However, the analysis and opinions expressed are our own.

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About the Author

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David Goldberg

Dave Goldberg is an automotive journalist and lifelong car fanatic. He writes for numerous enthusiast and business outlets and is an ongoing contributor to HotCars.com, one of the most popular car culture websites. When he’s not writing or driving, Dave is either under a hood or asleep. His credentials include a BA in Journalism from The George Washington University.

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P0456 Engine Code | Evaporative Emission Control System—Small Leak Detected

P0016 Engine Code | Camshaft and Crankshaft Not In Sync

Good luck

YMMV,

MidCow3

Doug007

This - happened to us with just about 500 miles on the odo. Tighten it down at least one click and it should clear.

websurfer

Yes, it was a weak 12V battery. Check the battery, it happen to me also. Did you leave the doors opened for a long time?

@midcow3 Thanks sharing that possible check engine page.

TheCDN

Some simple reasons as others have listed as well so I'm just repeating. 1 - loose gas cap OR you've opened the gas flap door and left it open. 2 - low voltage with your 12 volt battery. Both of these will clear after about 1/2 hour driving time as the system constantly does checks, that's if the issue has resolved itself, IE you've tightened the gas cap or closed the door flap, and or your battery has been recharged while driving. Both have happened to me, as well as a call from my dealer to see what was wrong! My dealer was alerted of the check engine light coming on and actually took the time to talk to me about it!

Please know that your 12 volt battery health is sketchy with the 2nd gen NX series. Lexus has plenty of background parasitic draw on the 12 volt battery when your car is shut off and if you don't drive it regularly it will get low in about a week or so. Also your dealer is supposed to fully charge a new vehicle's 12 volt battery as part of their pre inspection before you take delivery...this typically doesn't happen. Please note as well you have a 12 month or 12,000 mile battery condition check warranty on a new car as well. So dealer will do a thorough test of your 12 volt battery to determine if it is healthy or not. Running down a 12 volt battery is not good, and results in a shorter life span.

At the very least call your dealer and set up an appointment to find out what exactly has happened, this should surely be covered under warranty to find out what went wrong and how to prevent it happening in the future.