The human body runs on various systems. We have our circulatory system, skeletal system, respiratory system, and so on. We need each system to work properly to remain healthy. Our vehicles are the same. They contain a series of systems that work together to keep it functioning properly. Each system needs to be properly maintained and taken care of.

This is the third in a series of blogs we will be posting about the various vehicle systems and their function. Please also see:


The emission system keeps your vehicle’s engine running cleanly and efficiently in various operating conditions. It uses an array of sensors, computerized engine controls, and exhaust components to control your vehicle’s output of emissions, exhaust, and pollutants (including gasoline vapors that escape the fuel tank). The emissions system significantly reduces harmful gasses created by your vehicle such as carbon monoxide (CO), unburned hydrocarbons (HC), and oxides of nitrogen (NOx). By law, the emissions system must be maintained in proper operating condition.

Parts of The Emission System:

  • Catalytic converter and exhaust components
  • EGR valve and related components
  • PCV valve
  • Evaporative system
  • Oxygen sensors
  • Control Module
  • Gas cap


A steady flashing emission warning light on your vehicle dashboard indicates a problem is currently happening and requires immediate attention. Failure to do so can reduce your gas mileage and/or cause your vehicle to pollute.

Some factors that affect the emissions system include:

  • Driving and atmosphere conditions
  • Mileage
  • Vehicle age
  • Type of spark plug electrode material
  • Poor vehicle maintenance
  • Poor quality fuel
  • Damaged or worn sensors
  • Dry-rotted or cracked vacuum hoses

Any of these things can cause your vehicle to fail emissions. If you feel like you have a problem, have it worked on before your emissions test to avoid failing and the hassle of retesting.


In Idaho, the Division of Motor Vehicles (DMV) works with the state’s Department of Environmental Quality to regulate emissions control. Eligible vehicles registered in Ada County, Canyon County, and the city of Kuna are required to undergo emissions inspections every two years.

In Idaho, vehicles required to undergo inspection include:

  • Gasoline-powered vehicles model year 1981 or newer
  • Diesel-powered vehicles over 5 model years’ old

In Idaho, the following vehicles are exempt from emissions testing:

  • Vehicles under five model years’ old
  • Vehicles older than the model year 1981
  • Electric and hybrid vehicles
  • Vehicles that weigh less than 1,500 lbs.
  • Classic vehicles
  • Motor homes
  • Motorized farm equipment
  • Vehicles used solely for agriculture purposes

Shortly after you register your vehicle or renew your registration in Idaho you will get a notice to have your emissions tested and by what date. If you receive a second notice it is because you failed to have your vehicle tested by the date of the first notice. After the second (and final) notice, you will have 35 days to have your vehicle tested. If you fail to do so, your registration is revoked and you will be required to pay an additional processing fee of $10 when you have it texted if you are late. When it is time for an emissions test, you will need to bring your vehicle to an official testing station with the fee (the fee will not should not exceed $20) and any paperwork and identification required. If your vehicle passes, you will obtain a Vehicle Inspection Report, and your technician will tell you how to proceed from there.

Failed Vehicle Inspections:

Should your vehicle fail its emissions test, you are required to have it repaired and retested. The emissions technician should provide you with information as to why the vehicle failed and the repairs that are needed. You are permitted one free retest if you bring your vehicle to the same station within 30 days of the original test. Depending on your circumstances you may be eligible for a repair waiver or hardship waiver.

For more information on emissions testing in Ada county, you can visit the Air Quality Board of Ada County website.

At Meridian Automotive, we will diagnose the reason why your vehicle failed emissions and repair the vehicle. We can also re-test the vehicle to get the emissions certificate. Don’t trust just anyone with your emission repair services, trust the experts at Meridian Automotive. Call us today (208) 297-5573 or schedule an appointment online.

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