Why Is My Check Engine Light On?
The light itself doesn’t specify the problem; it’s simply an alert. The six most common causes of a check engine light are as follows:
-
A loose, damaged, or missing gas cap
-
Failed, or failing, O2 sensors
-
Spark plug, wiring, or ignition issues
-
Catalytic converter failure
-
A faulty battery or charging system
-
Transmission problems
Common Issues & How To Fix
You can check your own check engine light with an on-board diagnostics (OBD) scanner. OBD-II, the latest version of the technology, decodes to know if there’s a problem with one of its components. Like other construction lights, although if you don’t have an OBD reader, it’s still helpful to check for these common problems when your check engine light comes on.
A Loose Gas Cap
The check engine light isn’t caused by a faulty part or component, but rather by the fuel cap. This is the easiest issue to check. If the cap isn’t fully tightened or accidentally opened after filling up, the sensor will quickly trigger a dashboard warning. The cap can easily come loose in a rough, vibrating worksite environment.
Oxygen (O2) sensor failure
An oxygen sensor (O2) is used to detect the amount of unburned oxygen in an engine exhaust system. Our equipment can adjust the levels of oxygen and fuel vapors entering the engine. When the check engine light comes on, it shows that the oxygen sensor may fail.
The equipment will still work fine if the oxygen sensor fails, but the fuel consumption will be faster. Worse, other important components can also be damaged, such as catalytic converters, spark plugs, and other emission controls. Replacing the oxygen sensor will do the trick.
Dirty or Faulty Spark Plugs & Ignition Coils
The ignition coil and spark plug work together to ignite the fuel and oxygen vapors, starting the engine. In gasoline engines, a dirty spark plug, a damaged coil assembly, or poor wiring can cause an engine misfire. In diesel engines, similar issues are often related to a faulty glow plug (used for cold starting) or a faulty fuel injector. These issues can cause the engine to display a “check engine light on.”
Spark plugs and glow plugs are consumable parts and are relatively inexpensive to replace. They should be replaced according to the manufacturer’s maintenance schedule. An engine misfire should not be ignored.
Catalytic Converter Issues
Failing Mass Airflow Sensor
Your Mass Airflow Sensor (MAS or MAF) figures out how much air the engine needs to start and keep running. These MAF sensors get dirty pretty easily—so giving them a good, thorough clean might turn off your check engine light (CEL). But if that doesn’t fix the problem, the air-fuel mix will probably still be off, and you’ll need to replace the sensor.
When your check engine light comes on, make sure to check the MAF sensor first. Here’s why: most of the engine’s parts work together like a team. If one part fails, the others often end up having issues too.
Internal Engine Problems
Of course, serious internal problems can also cause the check engine light to illuminate. These problems shorten the engine’s life, such as low oil pressure, engine overheating, or compression loss due to worn piston rings or valve failure.
Internal engine problems require immediate professional assistance at the best. If the check engine light is on with a knocking sound, exhaust smoke, or a sudden power loss, stop the machine right now.
Use a Code Reader to Decode the Check Engine Light
Since the check engine light can indicate thousands of different conditions, guessing isn’t an effective strategy. The good way is to use an on-board diagnostic (OBD) code reader. Most modern heavy equipment is equipped with a diagnostic port (typically a 9-pin Deutsch connector, different from the OBD-II port in a car).
You can plug a compatible scanner into this port to retrieve diagnostic trouble codes (DTCs) stored in the ECU. The codes themselves are alphanumeric (e.g., P0420, SPN 1569 FMI 31) and correspond to a specific fault. You can look up the meaning of the code in the repair manual or online. It can help you locate the problem and even provide predictive analysis, suggesting maintenance. Using these advanced features can help you get ahead of potential problems, keeping your equipment in top shape.
Check Engine Light When It’s Static Vs. Flashing
Once your check engine light is on, whether it stays on or flashes, it shows that your equipment has a problem and needs to be repaired. There is a difference between them. A normally lit check engine light means you can drive safely without immediate repairs. However, if it flashes, stop driving immediately to avoid further damage. Please check out your owner’s manual (or look it up online) for the exact flashing sequence for your specific model.
| Light Status | Severity | Problems | Recommended Action |
|---|---|---|---|
| Static (Solid) | Less Serious | Loose Gas Cap, Oxygen Sensor Malfunction, Faulty EGR Valve, Minor Vacuum Leak | A fault has been detected. The issue is not an immediate emergency, but it should be diagnosed as soon as possible. |
| Flashing (Blinking) | Critical | Misfiring Engine, Catalytic Converter Failure, Overheating Engine, Low Oil Pressure | A severe problem is occurring that could cause immediate and expensive damage. Stop operating the machine safely now. |
Summary
FAQs
How long can you drive with the check engine light on?
If the light is solid, you can generally keep using the machine, but you should have it diagnosed as soon as possible. If the light is flashing, you should pull over and shut down the engine.
Can a check engine light fix itself?
Rarely. For a temporary glitch, the light might turn off after a few operating cycles. However, if a component fails, you will have to repair the problem to turn the light off.
What are machine diagnostic trouble codes (DTCs)?
DTCs are codes generated by the machine’s onboard computer. Each code has a specific problem. A good way to point a technician toward the source of the problem.
How to reset the check engine light?
Depending on your OBD-II scanner, you might be able to reset the code, which should turn the light off. However, if the problem isn’t resolved, the light may come back on.
