A smog check is a test designed to measure the emissions produced by your vehicle to ensure they meet California’s air quality standards. Smog checks are part of California’s efforts to combat air pollution and improve the environment. Smog checks are required for most vehicles during registration renewal or when transferring ownership. If your vehicle passes, the results are electronically sent to the DMV, and you can complete your registration.

A Brief History of Smog Checks

Smog checks originated in the 1970s when California began facing severe air pollution, especially in urban areas like our city Los Angeles. To address the problem, the state introduced the Clean Air Act in 1970, followed by the establishment of the California Air Resources Board (CARB) to regulate emissions standards. By 1984, smog checks became a mandatory part of vehicle registration, ensuring vehicles meet emission standards to reduce harmful pollutants. Today, the Bureau of Automotive Repair (BAR) oversees smog testing to ensure compliance with California Air Resources Board (CARB) regulations.

Preparing for a Smog Check

To help your vehicle test smoothly, here are some tips:

DMV Documentation: While it’s helpful to bring your DMV registration renewal notice, it’s not mandatory. We can process your test without it.

Ensure Readiness Monitors Are Set: Modern vehicles have onboard diagnostic systems (OBD-II) that must show readiness monitors as “complete” for a valid test. If your vehicle’s monitors aren’t ready, refer to your owner’s manual for the manufacturer’s recommended drive cycle to reset them. Common situations where monitors may not be ready include after a battery replacement or disconnection.

Know Your Vehicle’s Condition: Address dashboard warning lights and perform basic maintenance checks before your appointment.

Understanding Aftermarket Parts

Aftermarket parts are components not made by the vehicle’s original manufacturer. In California, these parts must be CARB-approved and carry an EO number to confirm they meet emissions standards for your vehicle’s make, model, and year. Non-compliant parts will cause the test to fail, requiring the vehicle to be brought into compliance and retested.

What Happens During a Smog Check at Our Shop

Arrival: Drive up to our designated bay (#4) and park as directed. Leave the keys in the car or hand them to our technician.

Paperwork: We’ll fill out an invoice for you to sign, granting permission to work on your vehicle.

Safety Checks: We chalk your vehicle to ensure safety and prevent movement during the test.

Emissions Testing: Using state-approved equipment, we:

Inspect all emissions-related components for compliance with California standards.

Verify that any aftermarket parts have the required CARB Executive Order (EO) numbers.

Run a series of diagnostic and functional tests.

Customer Comfort: While you wait, enjoy free water, comfy chairs, and free Wi-Fi.

We also have surprise perks—you’ll have to visit us and get your vehicle serviced to find out what they are!

Results: Once complete, we send the results to the state. If your vehicle passes, the smog certificate is sent electronically to the DMV.

We provide you with a copy of the results, the estimate, and the final invoice.

Next Steps After Passing

Once your vehicle passes:

Electronic Submission: Your smog certificate is automatically sent to the DMV.

DMV Follow-Up: If your registration fees are paid and there are no other tasks, your stickers should arrive by mail in about a week.

Immediate Options: Visit a DMV or AAA office (there’s one nearby on Grand Avenue) to pay fees and get stickers in person. 

What If Your Vehicle Gets a “Not Ready” Test Result?

If your vehicle receives a “Not Ready” result during the smog check, this means that one or more of its emissions monitors have not completed their self-checks. The vehicle cannot pass until the required monitors are in a “Ready” state.

What Are Emissions Monitors?

Emissions monitors are built-in system checks that track the performance of components like the catalytic converter, oxygen sensors, and EGR system. When a vehicle’s battery is disconnected, codes are cleared, or repairs are made, these monitors reset and need to be reactivated.

How to Get Your Monitors Ready

To ensure your vehicle passes the smog check, you will need to complete a drive cycle specific to your make and model. This typically involves:

Driving under various conditions (city, highway, and idle)

Maintaining steady speeds for a set duration

Avoiding abrupt stops or acceleration

The exact steps vary by vehicle, so check your owner’s manual or search online for your vehicle’s drive cycle procedure. Some monitors can take multiple drive cycles to reset.

Retesting After a “Not Ready” Result

Once your monitors show “Ready,” you’ll need to return for a retest. Since smog checks are required for DMV registration, be sure to allow yourself enough time to resolve monitor issues before your registration deadline.

Common Reasons Vehicles Fail

If your vehicle fails the smog check for any reason, it must be retested until it receives a passing result. Whether the issue is diagnostic trouble codes (DTCs), illegal modifications, or incomplete readiness monitors, the DMV requires a passing smog certificate before registration can be completed.

Diagnostic Trouble Codes (DTCs): The OBD-II system may detect issues like a malfunctioning catalytic converter or oxygen sensor. Failing codes will be listed on your test printout, which you can take to a mechanic for repairs. Use the BAR’s official site to find a licensed repair shop.

Modified or Tampered Systems: Illegal modifications (e.g., non-compliant exhaust systems) or tampered components (e.g., removed catalytic converters) will result in failure. Modifications must be CARB-compliant to pass.

Other Failures: Examples include missing emissions components, excessive emissions, or incomplete readiness monitors. Our team will explain your test results and provide guidance on next steps. 

A Cleaner California Starts Here

Smog checks are a vital part of maintaining cleaner air for everyone in California. At our shop on historic Route 66 in Glendora, we’re committed to making the process as smooth and straightforward as possible. Contact us at 626-551-4555 or stop by our location for any additional questions. Together, we can ensure your vehicle is running clean and compliant!