Why is my check engine light on?

Why is my Check Engine Light on?

Is it a important issue or something minor? Larry H. Miller Dodge RAM Havana is here to help with 5 reasons your Check Engine Light may go on. 

Oxygen Sensor
1. Your Oxygen (O2) Sensor is failing and will need to be replaced.
What is an O2 sensor? 
Your oxygen sensor measures the quantity of unburned oxygen in your vehicle's exhaust fumes. 
What will happen if I don't get the O2 sensor repaired? 
Your engine will be less fuel-efficient as it will be burning more fuel than it needs, and a defective O2 sensor can also harm your spark plugs and exhaust system.

Exhaust System & Catalytic Converter

2. Exhaust system needs replacing

What a Catalytic Converter? 

Basically it's your exhaust system converting carbon monoxide into carbon dioxide, making less of an impact on our atmosphere. 

What if I don't get my exhaust system repaired?

  • Your vehicle won't breeze through an emissions test. 
  • New vehicles are exempt for the first seven model years. 
  • Vehicles 8-11 years will be inspected using onboard diagnostics (OBD). If the check engine light is turned on, these vehicles will fail the inspection and need repairs. 
  • Learn more at EPA.
  • Rapid Screen roadside tests allow clean vehicles to skip emissions tests and this will be indicated on your registration renewal card. 
  • The current locations for Air Care Colorado Rapid Screen Roadside Trucks can be found here.

Spark Plugs & Wires

3. Spark Plugs or Plug Wires require repair. 
  • Spark plugs are an integral part of your vehicle's motor as they provide the spark that ignites the air and fuel mixture within the cylinders. This continuous ignition is what keeps your car moving down the road. 
  • If spark plugs are not checked with regular services, cleaned or changed when necessary, they can cause problems to occur with the engine. 
What are six signs you need to change your spark plugs?
  • Engine has a rough idle.
  • having trouble starting your car 
  • your engine misfires engine surges
  • High fuel consumption 
  • lack of acceleration
Worn attachments and fitting wires can bring about a stopped up exhaust system or harm to O2 sensors.

Mass Airflow Sensor

4. Mass Airflow Sensor may fail and need replacing.  If the sensor goes bad, the engine will not know the right amount of fuel to add, causing problems including poor gas mileage, lack of power and more.

What if I don't replace my Mass Airflow Sensor? 

  • All cars take outside air and pass it into the engine through the air filter. The mass airflow sensor measures the amount of air entering the engine
  • For an engine to perform properly, it needs a specific amount of air-fuel mixture
  • The computer in your car reads the amount of air coming into the engine from the mass airflow sensor and then calculates the correct amount of fuel needed for proper engine performance.
  • If the sensor goes bad, the engine will not know the right amount of fuel to add, causing problems including poor gas mileage, lack of power and more. 
  • If the air filter is dirty it is common for the mass airflow sensor to get dirty and lose the ability to read the amount of air coming in the engine. 
  • Routinely changing your air filter can improve the lifespan of your mass airflow sensor  

Check Gas Cap


Larry H. Miller Dodge Ram Havana

2727 S Havana St
Directions Denver, CO 80014

  • Sales: (888) 316-4774
  • Service: (877) 438-1263
  • Parts: (877) 887-2408

5. Check Your Gas Cap. Your gas cap may be the cause of your Check Engine Light illuminating. 

  • When it's loose or cracked, fuel vapors leak out and can throw the whole fuel system off. 
  • This causes a reduction in gas mileage and increases emissions.
  • If your car isn't feeling jerky, or surging when the check engine light comes on, the first thing you need to check is the gas cap. 
  • Pull your car over, unscrew the cap and take a look to see if it has any cracks in it, if no cracks retighten the cap. 
  • Continue driving and see if the check engine light turns off. While not threatening to your engine, it's good to take care of this right away to improve gas mileage.