How to Read the Results from Your Smog Check

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A smog check has 3 sections: A Visual Inspection; A Functional Inspection and an Emission Measurement Test. At the completion of the smog check, pass or fail the smog shop is required to provide you with a report of your vehicles test results. This article will focus on how to interpret the results of your smog check.

ASM Smog Check Results

The smog professional who performs the smog check will provide a Vehicle Inspection Report (VIR). The VIR shows the outcome for the three sections of your smog check. The ASM section will suggest each of the three harmful emissions (HC, CO, NOx) emitted by your car. The VIR is a typical diagnosis tool used by smog check professionals to ascertain likely causes and where to start testing further for an exact reason if you failed your smog check.

Toward the bottom of your automobile's VIR you will see the "ASM Exhaust Test Results". This area will show the exhaust results your automobile produced. This section of the VIR is shown below:

ASM section of a Vehicle Inspection Report from a smog check

"MAX" indicates the maximum emission allowed for the contaminant, based on your automobile's model year, engine size and vehicle weight.

"AVE" shows the average exhausts produced by cars of the same year, make and model.

"MEAS" (which is yellow on the image above) shows the measured emissions from your automobile. It is this measurement you have to be interested in in relation to the maximum level permitted in the MAX column. values in the MEAS column higher than the state's cut-off, or maximum limit, will trigger a smog check failure.

Each part of the ASM output report which identifies if your car passes or fails the smog check is color coded in the image above.

HC is Hydrocarbon. Hydrocarbons are basically raw fuel. If your vehicle is gasoline powered this is raw gas. If you fail your smog check because of high Hydrocarbon (HC) emissions it is most likely a sign of poor fuel ignition.

CO Carbon Monoxide. Carbon Monoxide is a result of partial combustion. If your vehicle exceeds the maximum limits it can be due to a number of emission failures.

NO Nitrous Oxide. Nitrous Oxide is created when an engine's combustion chamber temperature reaches over 2500 degrees Fahrenheit . As part of the vehicle manufacturers efforts to comply with emissions regulations they have implemented features, which if functioning properly lower nitrous oxide emissions enabling vehicles to pass smog checks.

If the reading in the MEAS column of the VIR from your smog check exceeds the value in the MAX column your vehicle will fail the smog check because of emissions failures. A PASS or FAIL value will be in the Results column highlighted in red in the image above.

CARBON DIOXIDE and O2 - Carbon Dioxide and Oxygen are measured too. These discharges do not have any bearing on whether your vehicle passes or fails a smog check.

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