In general, you will need to drive between 50-100 miles after you clear your cars computer. Hopefully, this will get rid of the check engine light once and for all. Some cars are ready for the test after driving about 50 miles, but others need more driving time (100-200 miles) before it is completely safe. Only looking for newer models? No check engine light on } Join 8,027 readers in helping fund MetaFilter. However, the consequences will vary from state to state. This can include dealership service centers, local mechanics, and other auto repair shops. Well about 75 miles did it. But if your cars a little older, or maybe not in perfect condition, here are some steps youll want to take to give the car its best chance at passing. Car owners might wonder how many miles to go after resetting the check engine light. The exact process varies from place to place and how old your car is, but a smog check generally includes having a technician look at your cars engine, exhaust, and emissions controls to make sure they work, scanning the cars computer to make sure it doesnt have any fault codes, and running the car on a dyno (like a treadmill) with a sniffing device in the tailpipe. How to pass smog? It all comes down to the way you are driving since there are some required criteria to make sure the cars computer shows correct readings on various sensors during testing. Running Right - Do not subject your vehicle to a smog inspection if it does not run right. Its important to note that the age and type of vehicle that meets exemption criteria differs from place to place. Guys says I have to drive about 300 miles to get the computer to get to pass? They include the BlueDriver Bluetooth OBD scanner, Hi-Gear catalytic converter cleaner, and Mechanix gloves. In many other cases, however, the issues that cause a failed smog check can also cause you to experience a drop in fuel economy, a rough idle, loss of power, or other issues with normal operation. Though vehicle smog inspection programs have been in effect for decades, many people remain mystified as to why their vehicle fails.