I don't know if the test can detect the code, but if your CEL is on, your car will fail the visual test. If the light isn't on and you take it in but not sure that your car will pass, do a "pre" test. Go to a guarantee to pass smog shop and for extra $$, they will do the equivalent of the pre test. If it doesn't pass, the tech should tell you why it didn't and recommend repairs and retest for free. If no pre test and you fail, you'll need to go to a smog only shop (as a gross polluter). Changing the oil and making sure your engine is hot before the test may help. Best if you don't have to shut off the engine before the test.