Ford F150 Check Engine Light-[All About it!!]

An issue related to your engine, especially the CEL, needs to be checked immediately.

The Ford F150 check engine light can come on due to loose gas caps, spark plugs, and ignition coils. The O2 or mass airflow sensor can be faulty too. A faulty exhaust system, ECU, or VVT switch can also trigger the CEL. Low or bad engine oil, vacuum leaks, and overheating might also be responsible.

But, that’s not all. So, stick with us till the end to know more. 

Why Is Ford F-150 Check Engine Light On?

Various malfunctions in your engine and related parts can trigger the check engine light. Here, we’ve briefly discussed the problems in the table below:

Loose Gas CapTighten or Replace Gas Cap
Bad Spark PlugsReplace Spark Plugs
Faulty Oxygen SensorReplace Oxygen Sensor
Low or Bad Engine OilRefill or Replace Engine Oil
Faulty Exhaust SystemFix Exhaust leak
Clean or Replace The Catalytic Converter
Faulty Ignition CoilReplace Ignition Coil
Vacuum LeaksFix Vacuum Leak
Faulty ECUContact Professional
VVT Switch and Solenoid FailureReplace Engine Oil
Replace Valve Body Assembly
Clean or Replace Solenoid
Overheating EngineFix Overheating Engine
Faulty Mass Airflow SensorClean or Replace Mass Airflow Sensor 
Old BatteryReplace or refurbish old battery

Now, let’s discuss these problems and solutions in detail. 

Reason 1: Loose Gas Cap

A loose gas cap allows fuel vapor to escape from the gas tank. It also allows dirt and debris to get in. Thus, the check engine light comes on. If that happens, you’ll notice a fuel smell from the vehicle.  

Solution: Tighten Or Replace The Gas Cap

If the gas cap is loose but not damaged, you can simply tighten it. But, if the gas cap is damaged, you must replace it. It’s a fairly easy process. 

Still, if you need some help, watch this video for details: 

These replacement procedures are general and may vary slightly depending on the specific model and year of the Ford F-150. It is important to refer to the owner’s manual or consult a professional if you have any questions or concerns.

Reason 2: Bad Spark Plugs

Bad spark plugs cause the engine to misfire. Thus, the check engine light comes on. When it happens, the vehicle won’t start properly. The acceleration will be slow while fuel consumption will be higher. Moreover, the engine may idle while driving. 

Solution: Replace Spark Plugs

Bad spark plugs simply need to be replaced. After disconnecting the battery, remove the wire or coil of the spark plug. Be sure to label the wire or coil to identify which spark plug it was attached with. Now, simply unscrew the spark plug with an 8 mm socket.

Wiggle out the ignition coil. Take a ⅝ spark plug socket and get the spark plug out. Get a new spark plug and coil boot for your F150. Thread it in the cavity and screw it in with your socket. Reconnect the wire or coil. And, you are done replacing your spark plugs.

Reason 3: Faulty Oxygen Sensor

Faulty Oxygen sensors are unable to measure the amount of unburnt oxygen in the exhaust system. Thus, the check engine light is triggered. 

Though you can drive safely with a faulty oxygen sensor, it’s not recommended. That’s because it decreases fuel efficiency and leads to costly repairs in the future.

Solution: Replace The Oxygen Sensor

Replacing the oxygen sensor is quite easy. After your Ford F150 is cooled down, raise it using a jack. Locate the oxygen sensor wire and disconnect the connector. Then, use a 22 mm wrench to unscrew the sensor.

Apply some anti-seize to the new sensor thread before screwing it in. Tighten it to the manufacturer’s specification with the same wrench. Finally, reconnect the connector. And, you’re done! For visuals, you can also watch this video:

Reason 4: Low or Bad Engine Oil

If the oil flowing through your engine is bad or insufficient, it’ll be detected. Thus, the check engine light will illuminate. 

In the case of low engine oil, you’ll see the oil pressure warning light on. Your engine will overheat and provide weaker performance. If the engine oil is bad, it’ll look dirty and darker. You’ll notice the oil smell and exhaust smoke. 

Solution: Refill or Replace Engine Oil

If the engine oil is low, simply refill it. Test if the engine oil is bad. If it is, replace it with new engine oil. For example, the Motorcraft SAE 5w20 Synthetic Blend Motor Oil is quite good for the F150. 

Fill the engine oil according to your engine’s capacity. For example, the 2.7L Ecoboost engine needs 6 quarts. But, the 3.0L EcoBoost engine needs 6.5 squats. If you need instructions, follow this video:

Reason 5: Faulty Exhaust System

The exhaust system doesn’t have a dedicated light. Thus, for any error code related to the exhaust system, the CEL will be illuminated. 

If the exhaust system is faulty, the vehicle will lose power. The acceleration will be loud and you’ll hear vibrating noises. The fuel efficiency will also be poor.  

Solution 1: Fix The Exhaust Leak

One of the most common problems with an exhaust system is exhaust leaks.

Solution 2: Clean or Replace The Catalytic Converter

If the catalytic converter is the problem, try cleaning it first. First, remove the catalytic converter. Take a bucket. Pour some laundry detergent and water into it to make a solution. Then dip the converter into it and let it soak overnight. 

The next day when you remove it, you’ll see the dirt is practically gone. The cloggings inside the converter will end. Just dry it up and reassemble it. Take it for a drive to see how it works. If nothing works, consider replacing the catalytic converter.

See this video for the comprehensive guide on replacing catalytic converters.

Reason 6: Faulty Ignition Coil

A malfunctioning ignition coil also causes a misfire in the engine. Thus, the check engine light comes on. In cases of engine misfires, the CEL might flash 8 times. 

Not only does it misfire, but also backfires. It sounds like a sharp cough or bang. You’ll also face hard starts. 

Solution: Replace The Ignition Coil

We have already discussed how to take the ignition coils out while replacing spark plugs. 

Now, take the new coil. If it’s not pre-greased, apply grease where it connects to the spark plug. Then, insert the coil and screw in the bolt. Reconnect the wire. Be sure that the new coil matches the old one. And, your ignition coil is replaced. 

Reason 7: Vacuum Leak

If there’s a vacuum leak in the car, there’ll be too much air in the engine. Thus, the check engine light illuminates. 

In case of vacuum leaks, you’ll notice rough idle, especially at lower RPMs. The engine will stall especially while stopping. You’ll also hear a hissing sound coming from the engine bay. 


Here are the steps to fix vacuum leaks in a car:

Step 1: Determine whether your car has a vacuum leak by monitoring the fuel trim data via a scan tool that displays live data.

Step 2: Locate the vacuum leak by visually inspecting the components and listening for any hissing sounds.

Step 3: Use soap and water to find leaks around the intake.

Step 3.1: You can also use an EVAP smoke machine to find leaks in the vacuum system.

Step 3.2: Again you can use a vacuum tester to check for leaks. It works especially in complex circuits and systems that are difficult to reach.

Step 6: Check the intake manifold for vacuum leaks.

Step 7: Replace any damaged or worn vacuum hoses or components.

Step 8: Reconnect any disconnected or loose vacuum hoses.

Step 9: Test the car to ensure that the vacuum leak has been fixed.

It is important to refer to the owner’s manual or consult a professional if you have any questions or concerns about fixing vacuum leaks in a car.

Reason 8: Faulty ECU

The ECU or Engine Control Unit keeps the engine working smoothly. It’s also in control of the dashboard warning lights. Thus, a faulty ECU will surely trigger the check engine light. 

A damaged ECU can cause problems while shifting gears in automatic transmission. The engine could also cut out and jerk while driving. The fuel economy also decreases. 

Solution: Contact Mechanic

If the ECU is faulty it will show some potential symptoms 

Fixing or replacing a faulty ECU is a complicated process and needs expert attention. Thus, I highly recommend contacting a professional for the procedure. 

Reason 9: VVT Switch and Solenoid Failure

A faulty variable switch and solenoid cause the engine to stumble. Especially under load or while climbing hills. You’ll also face rough engine idle. Thus, the check engine light comes on. 

Solution 1: Replace Engine Oil 

If the engine oil is bad, the VVT solenoid gets clogged. Thus, it fails to work properly. So, you’ll have to replace the engine oil and the solenoid should work properly. I’ve already mentioned how to do it beforehand.

Solution 2: Replace Valve Body Assembly

If the valve body assembly leaks, the oil doesn’t reach the cam assembly. If that’s the case, you’ll have to replace the valve body assembly. For that, first, you’ll have to remove the filter by unscrewing the two bolts. 

Then, remove the lever-type electrical connector going into the solenoids. Pull down the cooler assembly and the exhaust pipe a bit. It will gain access to the transmission pan. You’ll also have to remove the heat shields.

Now, you can remove the transmission pan. Then, unscrew the eight bolts of the valve body assembly and get it out. Give the vehicle some time to drain out the oil and then you can install your new valve body assembly. Just follow the procedure in reverse.

Solution 3: Clean or Replace Solenoid

Before completely replacing the solenoid, clean it to see if it works. Remove the solenoid from the vehicle. Connect the solenoid with a 9V battery and wires. While connected, the solenoid will open. Then, simply spray some cleaner into the hoses. 

You’ll see the dirt coming out of the solenoid. After it’s cleaned, put the solenoid back into the car to see if it works. If it still doesn’t, you’ll have to replace it. The same goes if the solenoid was damaged, to begin with. Here, you can watch this video for a guide:

Reason 10: Overheating Engine

Overheating can cause serious damage to the engine. Thus, the check engine light illuminates. If the engine is overheating, the temperature gauge reflects this. The temperature indicator rises towards red. 

You can also see steam, vapor, or smoke coming out of the hood. You may also notice a burning plastic or oil smell. 

A bunch of things might be causing these problems. Like a leaking radiator, rusty radiator cap, burnt cooling fan motor, or bad thermostat. The head gasket or the radiator itself may be bad too. 

Solution 1: Fix The Radiator Leak

First, check if the radiator is leaking. Take a pressure leak testing kit and stick it into the radiator. Pump it to about 16 lbs. to raise the pressure and see if fluids leak out. Also, check if the pressure keeps falling to ensure no leaks. 

Mostly the leak happens in the T connector and O ring of the hose. So, you’ll have to replace these parts. Here, you can follow this video:

Solution 2: Change Radiator Cap

A worn-out radiator cap won’t be able to hold pressure in. Thus, if they are rusty and worn out, change them. 

Solution 3: Change Cooling Fan Motor

Start up the car and set the AC to full. Check if the cooling fans are working properly. You can also connect jumper wires to the battery and the red cable of the motor. See if it spins. If it doesn’t, you’ll have to change the motor. 

Solution 4: Replace The Thermostat

To replace the thermostat, first release the spring cap on the thermostat housing. 

Disconnect the lower radiator hose. Then, remove the bolts of the lower inlet connection to remove the housing inlet. 

Then, you can pull out the old thermostat and O ring. Take your new thermostat and O ring. Lubricate the O ring with engine coolant. Then, place them in and reinstall everything back. 

Reason 11: Faulty Mass Airflow Sensor

With a faulty mass airflow sensor, the PCM miscalculates the amount of fuel the engine needs. Thus, the engine runs too lean and the check engine light comes on. 

When this sensor is bad, the engine is hard to turn over or start. You’ll experience excessive lean or rich idling. The engine will also hesitation during acceleration or under load. 

Solution: Clean or Replace Mass Airflow Sensor

Sometimes cleaning the airflow sensor is enough to make it work. First, locate the airflow sensor. It goes into the big intake box. Remove the plug of the sensor and the filter box. Remove it by popping out the red lever with a flathead screwdriver. 

Now, using a T20 bit, unbolt the MAF sensor. Take some mass airflow sensor cleaner. Spray it on the interior of the sensor a few times. Make sure that no dirt or debris is left. Put it back in. Attach the filter box and sensor plug. See if the problem is fixed.

If the problem remains, just replace the sensor with a new one. You can also watch this video for visuals: How to Replace Mass Air Flow Sensor 1997-2003 Ford F-150

Reason 12: Old Battery

If the battery is bad, the engine will be harder to crank and feel sluggish. Thus, the check engine light will be triggered. The car won’t hold a charge for much longer too. The dashboard lights will feel dim while the head and tail lights flicker. 

Solution: Repair or Replace Old Battery

Most batteries need to be replaced after three years. If not, after 4-5 years, they become completely unreliable. Here, the battery can either be replaced or refurbished. 

Replacing the battery is easy. After disconnecting the terminals, you just take out the old battery. Then, install the new battery and connect the terminals. On the other hand, refurbishing an old battery is more complex. 

Here, you have to take the sulfuric acid out of the battery. Filter the acid properly. Clean the battery insides with a solution of water and baking soda. Pour a bottle of battery reactivator into the battery. Then, pour back the filtered sulfuric acid.

The battery should be restored. You’ll have to slow charge it at 2A before installing. For the detailed process, watch this video: 

How To Read Ford Engine Codes?

You can check the engine codes with or without a scanner. Let’s see the process for both. 

With Scanner

Take the DLC connector and connect it under the dash of your car. Turn the car key on with the engine in the off position. From the scanner, press diagnosis and then read codes. The scanner will show you all the fault codes regarding your vehicle.

Note that the process may be a bit different depending on which scanner you use. 

Without Scanner

Turn the ignition key but don’t start the car. You’ll see the CEL flashing. It’ll flash for some time and then pause for 5 seconds. Write down how many times it flashes for four cycles. You’ll get a four-digit code. 

Call a car parts store and tell them this four-digit code. They’ll tell you the problem. Or you can search online to find a solution.

Common Check Engine Light Codes

Some common diagnostic codes cause the CEL to illuminate. Here, we have shown them in the table: 

P0171Engine receiving too much air
P0172Air/fuel mixture has too much fuel
P0173Fuel trim ratio too extreme
P0174Lean air/fuel mixture in Bank 2 of engine
P0175Rich air/fuel mixture in Bank 2 of engine
P0300Misfire in multiple cylinders
P0301Misfire in cylinder 1
P0302Misfire in cylinder 2
P0401Restricted EGR flow
P0402Too much flow in the EGR system
P0411Faulty secondary air injection pump filter, leaking secondary injection hose
P0420Malfunctioning Catalytic Converter, oxygen sensor, mass airflow sensor
P0430Same problem as P0420 but in Bank 2
P0440EVAP system malfunction
P0442Large leak in EVAP system
P0446Electrical circuit malfunction in the purge control valve
P0455EVAP system malfunction and lack of flow

Is It Safe to Drive With The Check Engine Light On?

It depends on the seriousness of the problem. The light can be red, orange, or yellow. 

The red light indicates a dangerous problem that needs to be fixed immediately. Orange and yellow lights are not as serious but should be checked to avoid future damage. 

Also, a steady engine light means the problem is major. However, a blinking light means that there is a minor problem.

But, should you just stop the car while driving as soon as you see the CEL? Even for repair, you might need to take the car to the store. Here, it should be okay to drive 50-100 miles with your check engine light on. 

How To Reset Check Engine Light?

If there are no issues with the engine, a simple reset should make the CEL go away. The same goes for after repairs. You can also reset the check engine light with or without the scanner.

Reset Using OBDII Scanner

After plugging in the OBDII scanner, scan it by reading the codes. Make sure that the ignition is on. Then, simply press erase codes or the erase button in your scanner. And, the reset should be done! Here’s a video for better understanding:

Reset Without Using Scanner

First, make sure the car and the anti-theft system are turned off. Disconnect the battery by removing the negative and positive car battery terminals. Always disconnect them in this order.

Next, turn on the car and press the horn button for a minute. It’ll drain any remaining power from the car’s electrical system. Reconnect the battery terminals and start the car to see if the check engine light has been reset.

If the check engine light is still on, drive the car for several miles to complete a drive cycle and see if the light turns off.


What Is The Difference Between Service Engine Light And Check Engine Light? 

Check engine light refers to a problem in your engine or exhaust system. On the other hand, the service engine light informs you about the next possible maintenance you’ll need. You should never ignore such errors and get it fixed as soon as possible.

Can Check Engine Light Be A Mistake?

Yes, the check engine light might be a mistake too. That means it’s detecting a problem that isn’t there. It might be triggered due to a loose wire or connection in the system. Although, if that’s the case, a simple reset should solve the problem. 

Can Check Engine Light Just Go Away?

No, the check engine light won’t go away unless you repair the problem. After repairing, the CEL should go away after 10-20 cycles. If there wasn’t any problem to begin with, the light will go away simply after a reset. 

Bottom Line!!

Hope you liked our article about Ford f150 check engine light. Still, we’d like you to know one last thing. In certain cases, you should take time to fix problems in your engine. Coolant should be added to an overheated engine after waiting for 30 minutes. Thanks for staying with us till the end. 

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William Baldwin

This Is William Baldwin, The Founder & Managing Editor of this website. Me and my team share automotive tips, tricks, and news

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Talha Atta

Talha Atta, a Mechanical Engineer and experienced technical content writer and editor at with a passion for the automotive industry.