If your check emissions system light is on while driving, it may remind you of an emissions system problem. Perhaps the simple fuel tank cap is not tightened, but it may also be that the catalytic converter needs to be replaced, which would cost more. As an owner, you should know what it means when the warning light to check your emissions system is on, what you can do about it, and how to deal with it.
What is the Check Emissions System Light?
Sometimes the parts are broken, sometimes it’s just some reason that makes the emissions exceed the limit. In fact, many cars produced after 1996 do not have a special emissions check system light, but instead remind drivers directly with the “Check Engine Light.” If you’re wondering what a check engine light means, it usually indicates that the engine control system has detected an issue that could affect performance or emissions. Because engine performance is directly linked to emissions, as long as the light is on, it’s most likely about emission-related problems. Ignoring this warning is not only bad for the environment but can also lead to higher fuel consumption and reduced power.
Causes of the Emissions System Warning Light On
Like other warning lights, there are several common reasons why your check emissions light may illuminate. Let’s take a closer look.
Loose or Damaged Gas Cap
That’s not a very bad situation. The vehicle’s fuel system was meant to be sealed, preventing gasoline vapors from escaping. But if the gas cap is not tightened, cracked, or the sealing ring is aged, the system will detect a leak and then light the warning light.
Failing Oxygen (O2) Sensor
That’s a common reason. The oxygen sensor detects how much unburned oxygen is left in the exhaust gas. The PCM (power control template) adjusts the ratio of oil to air, which makes the engine the most efficient. If the sensor fails, the data will be wrong. As a result, the air-fuel ratio is incorrect, fuel consumption becomes higher, and emissions also increase.
Bad Catalytic Converter
A catalytic converter is the core part of the emissions system. It turns harmful gases into relatively harmless gases. Over time, it can become clogged or contaminated, especially if other engine problems remain untreated for a long time. Once it wears out, it will affect the performance. Meanwhile, your exhaust gas fails to be detected.
Worn Spark Plugs or Ignition Coils
When the spark plug misfires, the fuel in the cylinder cannot burn sufficiently. The remaining fuel would end up in the exhaust pipe, overloading the catalytic converter and damaging it. The PCM will detect the misfire and light up the warning light.
Clogged Air Filter
Dirty air filters, though not directly changing exhaust emissions, can make the engine “breathe” poorly, with intake air not sufficient. It must cause an imbalance in the fuel-to-air ratio. The result is a drop in power, which may also trigger some warning lights, including the check emissions system light.
Faulty Mass Airflow (MAF) Sensor
MAF sensors monitor how much air is sucked into the engine. If the sensor is dirty or fails, the amount of air cannot be measured accurately, and the air-fuel ratio will be messed up, triggering the warning light.
Diagnosing the Emissions System Problem
The process can go from simple to complex, and find the problem step by step.
- Check the Simple Gas Cap: Before doing other checks, first check if the gas cap is tightened. Until you can hear a “click” to be in place. If the gas cap is cracked or the rubber ring is aged, get a new one. After fixing, the light may not go out immediately. After driving for a while, it will return to normal.
- Use an OBD-II Scanner: The most effective way is with an OBD-II scanner. Plug it into the interface under the dashboard, and you can see the fault code stored in the engine computer. For example, “P0420” is mostly related to the ternary catalytic converter, and “P0135” may be an oxygen sensor problem. These codes help you figure out where the problem is.
- Visual Inspection: Visible problems. For example, did the vacuum tube crack? Did the sensor’s wire wear or rust? Sometimes the fault is that simple, it’s just that the joint is loose or in poor contact.
- Seek Professional Help: If the fault code is not clear, or if the problem involves complex components or even the inside of the engine, just hand the car over to a professional. They have more advanced equipment and experience to find out problems faster and more accurately.
How Can I Prevent Emissions System Problems?
The best way to keep the Check Emission System light off is to nip it in the bud.
- Stick to Maintenance Schedule: Changing the oil on time, changing the spark plug, and cleaning the air filter element can all make the engine run in better condition and reduce emissions. If it’s heavy equipment, remember to clean or replace the diesel particulate filter (DPF) as recommended.
- Use High-Quality Fuel and Fluids: Cheap oil may have a lot of impurities, which can block the injector and damage the sensor. For diesel equipment, be sure to use sealed high-quality diesel exhaust treatment fluid (DEF) to prevent the SCR system from being contaminated.
- Don’t Ignore Other Warning Lights: An issue like an engine misfire or overheating problem can harm your catalytic converter.
- Watch for Unusual Signs: If you notice a loss of power, reduced fuel economy, or rough operation, it’s time to get it checked out. These are early signs of a problem.
Final Thought
The emissions system problem is worrying, but you can fix it with some expertise and high-quality parts from FridayParts. Includes air filter, gas cap, oxygen (O2) sensor, catalytic converter, and more. Compatible with numerous car brands. Contact us, and we will help you turn off the Check Emissions System light
People Also Ask
Can I still drive with my check emissions system light on?
Technically, you can, but we strongly advise against it. If the light is steady, it means a non-critical fault has been detected. You should get it checked as soon as possible. If the light is flashing, it indicates a severe problem, like a major engine misfire that could quickly destroy your catalytic converter. In that case, you should pull over and shut off the engine to prevent expensive damage. For heavy equipment, ignoring the light will often lead to the machine automatically reducing its power (an “engine derate”) until the issue is fixed.
How much does it cost to fix emissions system issues?
The cost varies dramatically. It could be free if it’s just a loose gas cap. A new oxygen sensor might cost a few hundred dollars for parts and labor. However, a catalytic converter replacement can easily exceed $1,000 or more, and a clogged DPF on a large machine can also be a very expensive repair.
How often should I have my emissions system checked?
There’s no need to have the system checked separately from your regular maintenance unless the warning light comes on. Routine service inspections will typically catch developing issues, and your vehicle’s onboard diagnostic system is designed to monitor them continuously.
Can a Check Emissions Light Illuminate for No Reason?
While rare, it can happen. A temporary sensor glitch or a brief communication error in the vehicle’s computer can sometimes trigger the light, which may then turn off on its own. However, you should never assume the light is on for “no reason.” It’s a critical warning system that should always be taken seriously and investigated.
