To ensure that vehicles run as clean and safe as possible, most countries have laws that mandate and regulate periodic vehicle inspections. In the United States, the laws governing inspections are controlled at the state level; 17 states require yearly or biannual safety inspections, and others require an inspection whenever ownership of a vehicle changes. In total, 31 states require some form of periodic inspection, which also often includes emissions testing.
What Does a Vehicle Safety Inspection Include?
The exact details of a safety inspection will vary from state to state, but most safety inspections cover the same components of your vehicle. The inspector isn’t likely to check the cleanliness of your cabin, but you should expect him or her to give your car a thorough pat-down on all of its key safety features. Typically, the following components will be inspected:
- Brakes: The inspector will check for worn or damaged drums, brake pads and brake lines.
- Lights and Turns Signals: The inspector will verify that your bulbs and other components meet the minimum standards of the law and that all of your signals work correctly.
- Steering and Suspension: The key structural components of your steering and suspension, such as your shocks, struts and engine mounts, should be in good condition without major wear. Your inspector will also check your fluid lines for leaks and make sure that the steering wheel has the correct amount of play to it.
- Wheels and Tires: Wheels must be structurally sound, and tires must have a satisfactory amount of tread depth left and be the correct type for the vehicle.
- Mirrors, Windows and Glass: The defroster must operate correctly, the front left window must be operable, and the windshield must be free of cracks, stickers and other visual impairments. The inspector will also verify that mirrors are sufficiently reflective and mounted securely to the vehicle.
- Exhaust System: The inspector will verify that all required components of the exhaust system are present and that there are no gas leaks between the engine and the tail pipe.
- Driver’s Seat and Restraints: The seat must be securely anchored to the floor of the cabin and in good condition. Seat belts, air bags and other restraint systems must adhere to legal standards for construction and quality.
- Fuel System: The inspector will ensure that all components of the fuel system are securely bolted to the vehicle and that there are no leaks present in the fuel system.
- Floor Pan: Holes that allow exhaust gases to enter the cabin or that present other safety hazards will cause a vehicle to fail inspection.
What’s Included in an Emissions Test?
Clean air regulations require that vehicles undergo periodic emissions testing to ensure that their pollution control systems are working correctly. There are three ways that vehicles are tested; the age, category, and other details of the vehicle determine which procedure is used. Regardless of vehicle details, however, emissions tests are usually broken into three steps.
Stage One: Visual Inspection
The first stage of the emissions test is the same for all vehicles. Typically, the inspector asks you to wait outside of your vehicle while he performs a visual check on your car. In this check, he will verify that all components of your pollution control system are present and that there are no major leaks or other safety hazards, such as bald tires, that might make the rest of the test unsafe. Finally, the inspector will reference your VIN to determine the emissions standards for your vehicle.
Stage Two: Emissions Test
The second stage of the test will actually measure your vehicle’s emissions, and the exact procedure will change depending on your vehicle.
- New Vehicles: Gasoline cars manufactured after 1996 and diesel vehicles manufactured after 1997 typically have an onboard computer that collects emissions data. Emissions inspectors can simply connect to the OBD II port with a handheld device and collect the data from the computer.
- Dynamometer Test: If the vehicle doesn’t have an onboard computer, the emissions test is performed on a dynamometer, a treadmill-like device that allows cars to drive in a stationary position. After you drive onto the machine, the inspector will insert a probe into your tail pipe and ask you to drive at a simulated speed of approximately 25 mph. The probe allows the inspector to analyze your exhaust and determine whether your pollution control system is working properly.
- Idle Test: If your vehicle can’t be driven onto a dynamometer due to its size or other characteristics, you’ll be asked to perform a similar procedure. However, instead of driving on a dynamometer, you’ll instead simply keep your car in idle and rev your engine according to the inspector’s instructions.
Stage Three: Gas Cap Test
The final stage of the emissions test ensures that your gas cap doesn’t allow vapors to escape from your fuel tank. The inspector removes your gas cap and connects it to a specially designed tool that measures the cap’s performance. If your cap can withstand the mandated pressure levels and your vehicle has passed the rest of the emissions test, you will be given a passing grade on your emissions test.
Why Do Cars Fail Emissions Tests?
There are a number of conditions that can cause a vehicle to fail an emissions test. Some of these issues are simple and relatively inexpensive to address. Other conditions may require more substantial repairs before your vehicle can successfully pass a tail pipe test.
- Air to Fuel Ratio: If the ratio of air to fuel in your engine is incorrect, your fuel won’t combust correctly and may emit more pollution than it should.
- Vacuum Leak: If your engine’s vacuum lines are leaking, your engine will burn fuel inefficiently and emit more pollutants.
- Ignition Timing: Optimum fuel efficiency requires precise timing of your car’s ignition system. If your timing is off, your engine will suffer from incomplete combustion and increased pollutants.
- Spark Plugs: Malfunctioning spark plugs can also cause incomplete combustion.
- Oxygen Sensor: If the oxygen sensor is malfunctioning, your vehicle won’t be able to make the correct adjustments to its combustion system and may emit more pollutants than necessary.
- Dirty Engine Oil: Contaminated oil can reduce efficiency.
- Clogged Air Filter: A clogged air filter can reduce air flow to the engine and imbalance the air to fuel ratio.
- Malfunctioning Engine Parts: A damaged engine can’t run at optimum efficiency.
- Catalytic Converter: Your car’s catalytic converter scrubs your exhaust before it leaves your tail pipe. If the converter isn’t working correctly, your emissions will be higher.
- Positive Crankcase Ventilation: If the valve of your PCV system is malfunctioning, waste gases can escape from your engine while still containing burnable gasoline, reducing efficiency and increasing emissions.
- Exhaust Gas Recirculation: Your EGR system increases efficiency and reduces emissions, so it can cause problems when the system malfunctions.
What Happens if I Fail an Emissions Test?
The consequences of failing an emissions test vary based on the state. Typically, emissions tests are required in conjunction with vehicle registration; if your car fails emissions, your registration may be denied. You’ll have a grace period in which you can have your car repaired and re-tested; failing to do so may cause your vehicle’s license plates to expire and make it illegal to drive.
How to Prepare for an Inspection
If you know or suspect that you’ll need to have your car inspected before your next registration renewal, don’t wait until you receive your inspection letter. Check with your local DMV to determine the requirements for your car to pass inspections. Perform an inspection yourself using the DMV’s checklist and address any issues before you go for your official inspection.
Begin by fixing any issues that you can find with a simple visual check. Have any chips or cracks in your windshield repaired, or replace the windshield if the damage is too great. Remove any obstructions that could impair your vision. You’ll also want to check your owner’s manual for recommended tire and wheel sizes and make sure that your wheels are compliant. If your tires are approaching the end of their life, purchase new tires before your inspection.
After you’ve addressed any obvious issues, have your car’s engine serviced. Change the oil and the air filter, and check for any signs that your spark plugs are malfunctioning. If your car has an onboard computer, you can also take it to an auto parts store and have them connect an OBD reader to your car to check for any fault codes or other errors that might indicate a problem with your emissions control system.
Vehicle inspections may be a hassle, but they ensure that every car on the road is as safe and clean as possible. Failing to pass an inspection can restrict your ability to drive, so find out whether your state requires inspections before you receive an unexpected inspections notice. Keeping your car in good condition and performing regular maintenance can ensure that you never have to fear an inspection and emissions test.