How to Pass the Emissions Test

Nobody wants to fail an outlier or smog test: that means you have to figure out what caused the failure and fix it. You then need to come back to retest.

Most states require smog tests before renewal. Requirements vary from state to state: some states require you to take a test every year, others may require you to take a test every two years. Other states may require a vehicle to reach a certain age before a test is required. You can check your state's requirements with your local DMV.

Testing for smog or emissions was introduced in the 1970s when the Clean Air Act went into effect. Smog checks confirm that the vehicle's emissions system is working properly and the vehicle is not emitting pollutants into the air.

If you're worried that your car might not pass the next smog test, there are steps you can take to increase your chances of a passing score. Here are a few tips to help make sure your car doesn't get dirty on your next smog test.

Part 1 of 1: Preparing the Vehicle for an Emissions Test

Step 1: Clear the Check Engine light if it is on. The Check Engine light is almost entirely related to your emissions system.

If this particular warning light is on, you will need to have the vehicle inspected and repaired before sending it in for a smog check. In almost all cases, the vehicle will fail if the Check Engine light comes on.

One of the most common reasons why the Check Engine light comes on is a faulty oxygen sensor. The oxygen sensor monitors the mixture of gas and air supplied to the fuel injectors, so the mixture can be adjusted if it is running rich or lean. A faulty oxygen sensor will cause the smog check to fail.

Replacing the oxygen sensor is a relatively affordable repair. Ignoring an oxygen sensor failure can result in catalytic converter damage that is very expensive to repair.

The takeaway here is to fix any issues with the Check Engine light before heading out for a smog test.

Step 2: Drive the car. The vehicle must be driven at highway speed for approximately two weeks before being submitted for a smog test.

Driving at higher speeds heats up the catalytic converter enough to burn off any remaining oil and gas. The catalytic converter converts harmful emissions before they leave the tailpipe.

City driving does not allow the converter to heat up enough to fully do its job, so when driving on the highway, gasoline and the remaining oil in the converter are burned. This will help the car pass the smog test.

Step 3: Change the oil before the smog test. Although this does not guarantee a positive result, dirty oil can release additional contaminants.

Step 4: Set up the car about two weeks before the test.. Replace all filters and have a mechanic inspect all hoses to make sure there are no cracks or breaks.

• Attention: In many cases, the mechanic disconnects the battery while doing a tune-up, which causes the car's computer to reboot. The vehicle then needs to be driven for a couple of weeks to have enough diagnostic data for a smog test.

Step 5 Check your tires to make sure they are properly inflated.. Most states do dynamometer testing of the car, which puts the car's tires on rollers to allow the engine to run at high speeds without moving.

Under-inflated tires will make the engine work harder and can affect your results.

Step 6: Inspect the gas cap. The gas tank cap covers the fuel system and if it is cracked or installed incorrectly, the Check Engine light will come on. This will cause your vehicle to fail the smog test. If the cap is damaged, replace it before testing.

Step 7: Consider using a fuel additive that can help reduce emissions.. Fuel additives are usually poured directly into the gas tank when refueling a car.

Additives are cleaned of carbon deposits that accumulate in the intake and exhaust system. It can also help the car pass the smog test.

Step 8: Submit your vehicle for a pre-test. In some states, smog check stations do pre-testing.

These tests test the emission system in the same way as the standard tests, but the results are not recorded in the DMV. This is a sure way to check if your vehicle will pass.

Although there is a charge for the pre-test, if you have serious doubts about your vehicle's chances of passing the pre-test, it is highly recommended that you take the pre-test. So you can have the car repaired before the official test.

Step 9: Drive your car at highway speed for at least 20 minutes before you arrive at the smog check station.. This will warm up the car and ensure it runs properly. It also warms up the combustion and exhaust system before testing.

Step 10: Have a licensed mechanic fix any problems if your vehicle fails an emissions test.. Our experienced mobile mechanics will be happy to come to your home or office to make any necessary repairs or adjustments to make sure you pass your second smog test. If you take the time to make sure your vehicle is prepared for an emissions test, you won't have to deal with the anxiety and potential embarrassment, not to mention the inconvenience of failing the test. We hope that with the steps listed above, you will be able to prepare your car for the emission test without any problems.