How to Help Your Car (Finally) Pass a Smog Test

california smog test graphic

Every other year, drivers in California open their car registration form to find those three dreaded words: Smog check required. While the testing requirement is beneficial to our clean air and overall health, it can also be anxiety inducing, especially if your car is more than a few years old or isn’t running as well as it used to.

The good news is that there are some steps you can take to give your car a better chance at passing the smog test. The first tip is to not wait until the last minute—if your car fails and requires repairs, you’ll need to have it ready to re-test before your registration deadline in order to avoid late fees. Here are some other tips on how to pass a smog test:

1.  Address the “check engine” light

If the “check engine” light is illuminated, your car will fail automatically regardless of the underlying reason. But don’t worry—the “check engine” light doesn’t necessarily mean an expensive repair is in your future. It could be something as simple as a faulty oxygen sensor. So go ahead and ask your auto mechanic to look into it. The relief of seeing that light go off will be worth it.

2. Get an oil change

Dirty oil might release extra pollutants during the smog test, so it’s a good idea to get a fresh batch of oil and a new filter installed in your car before you head to the testing station. Also, ask the oil change technician to visually inspect the engine to ensure there are no disconnected, cracked, or otherwise damaged hoses that could also result in a smog test failure.

3. Fill up coolant and gas tanks

As part of the smog test, the technician will run your car at high speeds while it remains in place. That means less air flowing through the radiator to cool it, which could be a problem if your coolant tank isn’t full. A low level of gas in your tank is also risky, as there’s a chance the fuel pump could be exposed and leak vapor into the fuel line, which would be an automatic test failure.

4. Drive at highway speeds two weeks before the test

The catalytic converter transforms pollutants in the exhaust system into less harmful emissions, but your car needs to run at high temperatures in order for the catalytic converter to burn out oil and gas residues. For this reason, you should drive your car at highway speeds several times in the weeks leading up to the smog test. Short trips at low speeds will leave residues in place, which could end up causing your car to fail the smog test.

5. Schedule a tune-up well in advance of the smog test

It’s a great idea to get a tune-up and address minor repair issues before taking your car in for a smog test, but be sure to schedule this at least two weeks in advance of the test. This is because mechanics usually disconnect the car battery during the tune-up, which will reset the car’s onboard computer. Your car needs at least two weeks of driving time to run the internal diagnostic testing that must be complete to pass a smog test.  

Where can you get a smog check in San Diego?

If you’re looking for a certified STAR smog check station that also offers affordable repairs for smog or other car issues, Chris’s Auto Smog & Repair Center is here to help. Our professional team of technicians can explain all the smog check rules to help your car pass, and perform any needed repairs quickly and efficiently.  Give us a call at (858) 270-1888 to set up an appointment today.