Is your Ford check engine light staying on? Ford Check Engine Light (CEL), also known as service engine soon (SES) warning, will stay on if a problem has been detected by the On-Board Diagnostic System (OBD-II).

Under normal operation, Ford check engine light will turn on when you turn on the ignition but should turn off and stay off once you start the engine.


Here are some of the most common symptoms owners notice when their Ford check engine light stays on.

  • Ford may idle or run rough
  • A decrease in fuel economy
  • The engine won't stay running
  • Ford loses power or is stuck in gear
  • Hesitates during acceleration
  • Powertrain malfunction/Reduced power - this message comes on when a powertrain problem has been detected.

In some cases, the Ford check engine light comes on and no other symptoms are noticed.


This is a list of the most common problems that trigger Ford check engine light to stay on. 

  • Loose gas cap
  • Oxygen sensor
  • Spark plus 
  • Mass airflow sensor
  • Catalytic converter
  • Vacuum leak 

There are hundreds of possible causes that will turn on Ford check engine light. To find out why the check engine light is on in your Ford read the fault codes. 

How to Diagnose Ford Check Engine Light 

The first step in troubleshooting the check engine light is to read the fault codes with an OBD-II scanner

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  1. Locate the diagnostics port under the dashboard of your Ford.Ford OBD II port locaiton Missing media item.
  2. Connect your OBD-II scanner into the diagnostics port. Turn on the ignition by pressing the Start button without pressing the brake pedal. turn on ignition to read ford check engine light
  3. Allow the scanner to power up and select Ford from the main menu then OBD-II. check engine lgiht Ford
  4. Select Engine Module then press read to retrieve codes that have triggered your Ford check engine light. These are the codes that have triggered the check engine light on your Ford.
  5. Once you fix the problem that triggered the code, come back to the main menu and select Erase Fault Data.erase ford check engine light


Your Ford check engine light on causes vary. Without reading Ford check engine diagnostic trouble codes (DTC) it is difficult to know what the problem is.


These instructions work on 1996 and newer Ford vehicles including Ford Mustang, Focus, Fiesta, F-150, Ranger, Explorer, EcoSport, Escape, Fusion, F250, Expedition, Edge, Transit, Taurus, Flex, Shelby GT, C-Max etc.

Common Problems

Loose Gas Cap

Loose gas cap triggers Ford check engine light

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One of the most common triggers of the check engine light on Ford vehicle is a loose gas cap. If you recently stopped at a gas station, make sure the gas cap was properly tightened.

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In some cases, the O ring in the fuel cap gets damaged. If that's the case, you will need to replace the fuel cap. You can use an OBD-II scanner or drive the vehicle for a few days for your Ford engine computer to reset the check engine light.

Newer Ford vehicles equipped with Easy Fuel have no gas cap at all.

Mass Air Flow Sensor

ford check engine light on due to maf sensor


Often referred to as the MAF sensor, the mass airflow sensor can fail triggering Ford check engine light to come on. If your Ford MAF sensor is defective, you will notice engine hesitation during acceleration and a dramatic decrease in fuel economy.

Typical codes stored in the ECU when the MAF fails are P0171 and P0174. Resetting these codes by disconnecting the battery for a few minutes does not fix the problem. In a few cases, you may be able to fix this problem by using a MAF sensor cleaner. The recommended fix is to replace your Ford Mass Air Flow Sensor with a new OEM Ford unit. Aftermarket Ford MAF sensors can sometimes malfunction even when brand new.

Oxygen Sensor

The oxygen sensors (O2) mounted on the catalytic converter can fail to cause the check engine light to come on, poor engine performance and a decrease in fuel economy.

One of the most common Ford codes related to the oxygen sensor is P0132 caused by an oxygen sensor circuit high voltage.

VCTR Solenoid

A common problem that is known to trigger the check engine light on Ford vehicles, especially Fusions equipped with the 4 cylinder engine is a defective Variable Camshaft Timing solenoid also known as VCT solenoid.

A defective VCT solenoid will cause the engine to run rough and trigger the check engine light at the same time. The code related to this problem is usually P0012 - "A" Camshaft Position - Timing Over-Retarded (Bank 1). Related codes include P0011, P0010, P0013, P0014.

Ignition Coils

The ignition coils may fail triggering Ford check engine light to come on. Common symptoms include not only check engine light on but engine misfire, running rough and fault codes ranging from P0300 through P03012.

It is recommended to change the spark plug boots at the same time. If your Ford check engine light stays on after replacing the ignition coils check the MAF sensor, spark plugs, catalytic converter, and the ECU.

Check Engine Light Flashing, Engine Shakes


Ford Engine

If the check engine or service engine light is flashing, it means that the OBD-II system has detected an engine misfire. This is often caused by a bad spark plug or defective ignition coil but can be caused by other issues as well.

What is happening when your Ford check engine light is flashing is that fuel is not getting burned in the cylinder but is existing unburned and typically gets burned at the catalytic converter.

Avoid driving your Ford if the check engine light is flashing as this condition may cause unnecessary damage to the engine and the catalytic converter.

Ford Check Engine Light Flashing 8 Times

If your Ford check engine light blinks eight times when you turn on the ignition, it means that the vehicle is not ready for State Emission Inspection, I/M test. This typically happens if the codes were recently erased with an OBD-II scanner or the battery was disconnected.

As long as the lights stop blinking after eight flashes, you can continue to drive the vehicle. Within a few driving cycles, all systems should be tested and the CEL should no long flash at startup.


  • Can I reset the check engine light by disconnecting the car battery?
    • Yes, disconnecting the battery usually clear the ECU codes. By turning the check engine light off this way you will not fix the problem. If you believe the check engine light needs to be off, drive the car for a few days and the CEL will reset itself. The Onboard Diagnostic System in your car continually monitors your vehicle and will turn off the CEL if the problem is solved. If the problem hasn't been resolved, even if you disconnect the battery, the CEL will come back up again which can be as soon as you restart the car or up to a few days.
  • Will my car pass safety emissions if the check engine light is on, or recently reset?
    • If the check engine light is on, it will not pass the emission inspection/smog test. If the light was recently reset with an OBD2 scanner or by disconnecting the battery, you need to drive the car for a couple of days for the systems to be ready for testing.
  • Check engine light is on but no codes?
    • It could be because you are using an OBD2 scanner that does not support the protocol used in your car. Try a different scanner. Also, there may be an issue communicating with the ECU due to a damaged wire or ECU malfunction.
  • Would the check engine light on cause the car to not start?
    • No. The check engine light is not the reason why the car doesn't start. If the car doesn't start, read the codes and maybe the CEL will give you a code that can help you diagnose the car. Clearing codes will not make your car start.
  • Why is my check engine light came on after oil change?
    • It may be just bad timing. An oil change is not going to trigger the CEL. Unless MAYBE a sensor got accidentally unplugged, disconnected or damaged during the oil change. Take your car back to the auto repair shop that changed your oil and have them diagnose the problem.
  • Is it normal for the check engine light to turn on after repair service?
    • No, the CEL should not turn on after routine maintenance. If you modified your engine, transmission, exhaust, intake, fuel system or other systems it can affect engine and emission control system, causing a check engine or service engine soon light to come on. CEL should not come on if you changed tires or tire size.
  • Why is my check engine light on after replacing the battery?
    • Drive the car for a couple of days and allow the ECU to reset itself. If the CEL still remains on, read codes.
  • Why did my check engine light turn on when the engine overheated?
    • The check engine light is trying to tell you that there is a problem with your engine. It could be low coolant, stuck thermostat, transmission not shifting. Figure out why your car is overheating first and address that problem. DO NOT CONTINUE TO DRIVE IF YOUR CAR OVERHEATS.

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Member since 2020-08

2015 F350XL gas engine. Dead battery. Replaced battery--truck will NOT start (console displays STARTING SYSTEM FAULT). Terminals clean & tight. No corrosion. All fuses verified good. My CEL flashes 8 times when Ignition key is turned but no Start. Also tried jump start from another vehicle--no Start. All lights, wipers, etc operate so electrical power is available. Cannot OBD because computer memory was cleared--no record of codes available. Any ideas? Please!