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Home » FAQ » Why Did My Catalytic Converter Fail The Smog Check?

 Why did my catalytic converter fail the smog check?

 Typically, a catalytic converter which fails the smog check falls in to one of the following categories:

  • Aging or lack of engine maintenance – cycles of damaging engine conditions will eventually deteriorate the catalytic converter performance
  • Physical damage due to corrosion, or from the catalytic converter hitting an object on the road surface
  • Contamination – the catalytic converter is contaminated due to excessive oil consumption, internal coolant leak, or excessive carbon build up
  • Melted substrate – engine misfires lead to excessive catalytic converter temperatures
  • Thermo quenching – the hot catalytic converter is cold-quenched when driving through deep water or into deep snow

What are the symptoms and the causes of a defective catalytic converter?

  • Symptom: a loss of engine power over 15-20 miles per hour
    Cause: the catalytic converter is plugged up thus restricting the exhaust flow 
  • Symptom: a strong sulfur or egg smell from a good running engine
    Cause: the catalytic converter is not completing the burning process properly
  • Symptom: a rattle can be heard from the catalytic converter during idle and acceleration 
    Cause: the catalytic substrate is broken down and possibly plugged

How do I find out if my catalytic converter is defective?

The most practical way to find out whether a catalytic converter is defective is to visit a local smog station and have the smog technician perform a Smog Check and inspect your catalytic converter using the station’s smog machine (BAR-97 Unit) or stand-alone 5 exhaust gas analyzer. Note that such tools are expensive and not designed for home use. 

What is the California Smog Check Program?

The California Smog Check Program is an important part of the State’s efforts to improve the quality of the air we breathe in the state. The California Smog Check Program removes hundreds of tons of smog-forming pollutants from California’s air every day.

Because of the California Smog Check Program, the Department of Motor Vehicles sends periodically a registration renewal notice which indicates if a smog check is required. If the DMV requires a smog check for a vehicle, the owner must comply with the notice within 90 days. Following the smog check, the vehicle owner can provide a completed smog check certificate.

Smog Check inspections are designed to identify vehicles with excess emissions, so they can be repaired. Once properly repaired, these vehicles can meet state and federal emissions legal standards. These are often labelled California legal, California compliant, or CARB compliant. 

A smog check inspection is performed by a station that has been licensed by the California Bureau of Automotive Repair. Depending on the situation, the owner may be required to take the vehicle to one of the following types of smog check stations:

  • Test-and-repair stations can both perform the smog check and repair the vehicle
  • Repair-only stations can only repair the vehicle but cannot perform the test itself
  • Test-only stations can perform the smog check test but cannot make repairs
  • STAR stations meet higher performance standards. Some STAR stations are test-only stations, while other STAR stations are test-and-repair

Registration will not be renewed until a smog check certificate is provided by the vehicle’s owner following the smog test check. If the vehicle fails the smog check, the owner will be required to complete all necessary repairs and pass a smog check test again to complete the registration. If the costs of repairing the vehicle outweigh its value, the state may buy it, and have it scrapped. The buyback program is part of California’s Consumer Assistance Program that also offers consumer assistance for repairs related to smog check.

The California Smog Check Program is entirely administered by the California Department of Consumer Affairs’ Bureau of Automotive Repair.

Ready To Replace Your Catalytic Converter?

For the best performance and a longer product life, we recommend maintaining your engine and your catalytic converter on a regular basis. Shop our premium brands including Magnaflow, Bosal, Walker, and more, at unbeatable prices. 

Need help picking the right catalytic converter? Our mechanically trained experts are ready to help you every step of the way. Our customer service team is available through phone, chat or email Monday – Friday 5 am – 5 pm (Pacific Time).

Call us today at: 855-592-9378.