OLR Research Report

February 1, 2008




By: James J. Fazzalaro, Principal Analyst

You asked us to compare certain characteristics of the previous and current motor vehicle emissions inspection programs in Connecticut. These characteristics include the way the program is set up, the types of inspections performed, the conditions for granting a waiver from compliance, and vehicles exempt from inspection. You also wanted an explanation of why a vehicle is considered to have failed its test when it reports for an inspection and its “check engine” light is on.


From 1983 until June 30, 2002, when its contract with Envirotest expired, the state's motor vehicle emissions inspection program consisted of a centralized system operated by an independent contractor (the “old” system). The 25 testing locations in the old system were owned and operated by Envirotest, which was paid a per vehicle test fee. Following expiration of the contract, the state replaced the centralized system with a decentralized system under which inspections are performed at approximately 300 state-licensed motor vehicle dealer and repairer locations authorized by the Department of Motor Vehicles (DMV) to perform inspections (the “new” system). The new system began operating on October 17, 2003.

Under the old system, all vehicles subject to inspection were given the same type of test. A probe was inserted into the vehicle's tailpipe and exhaust emissions were sampled while the vehicle idled. If it failed this test, the vehicle was run at a simulated highway speed and the exhaust was sampled again. Under the new system, there are three types of tests performed depending on the vehicle's age and characteristics. The primary test for vehicles that are 1996 and newer is called an Onboard Diagnostics Test where the test computer downloads certain information from a computer module on the vehicle. The data shows how the vehicle is functioning, including its emissions system. Older vehicles and newer vehicles that cannot be successfully connected to the computer receive a tailpipe test that samples emissions based on simulated highway operation. Certain vehicles that cannot be inspected in this simulation mode, such as all-wheel drive vehicles, get a tailpipe test that is similar in some ways to the test that was performed under the old system.

The old emissions inspection program initially applied to all gasoline powered vehicles weighing up to 10,000 pounds. Diesel-powered vehicles, vehicles manufactured before the 1968 model year, new vehicles for the first model year, and a few other vehicle categories were exempt. The exemption provisions of the law changed over the years so that by the time the old program ended, diesel-powered vehicles up to 10,000 pounds became subject to inspection and any vehicle that was at least 25 years old became exempt. These exemptions carried over into the new program and an additional exemption was added for a new vehicle for its first four model years from manufacture.

The old system used a windshield sticker based enforcement system. A vehicle had to display a windshield sticker showing its compliance status and vehicles not in compliance could be ticketed. The new system is capable of providing real-time information on a vehicle's compliance status through the Department of Motor Vehicle's registration database. Thus, while someone can still be cited for noncompliance, under the new system there is the additional sanction available of denial of registration renewal for a noncompliant vehicle.

Under the old system, someone could qualify for a waiver from compliance based on “unreasonable cost of repair.” When the program first started, the law set this at a cost of $40. But in 1989, new federal regulations took effect that required a minimum cost of repair of $450 adjusted annually for inflation. The legislature changed the law in 1993 to require the repair cost threshold to reflect the federal requirement. The current repair cost requirement of $660 reflects this inflation-adjusted amount and was carried over from the old to the new program.

The waiver process was essentially carried over from the old to the new programs with some additions to comply with the federal requirements. There are three types of waivers available. One is for unreasonable cost of repair. A vehicle owner can also apply for what is called a diagnostic waiver. Under this option, the vehicle is submitted for a complete physical and functional diagnosis and it receives a waiver if the examination indicates that no additional repairs are required. The third type of waiver is granted for economic hardship. Someone applying for a hardship waiver must meet certain income and other criteria. A hardship waiver is only a temporary extension of time, generally only until the vehicle is due for its next inspection.

The “check engine” light on 1996 and newer motor vehicles is part of their onboard diagnostics system. One of the primary functions of the light is to go on when the vehicle's diagnostic sensors detect problems or malfunctions in any of its emissions control equipment or systems that cause the vehicle to emit more than 150% of the maximum hydrocarbon emissions set for it by federal standards. The federal requirements for the onboard diagnostic test procedure specify that conditions that cause a vehicle's computer to light up its “check engine” light indicate conditions that make it exceed its maximum allowable pollution levels, and therefore it has failed its inspection.


As noted above, the old system was centralized. A single private contractor operated all of the 25 testing locations throughout the state and conducted all of the emissions tests. The contractor collected the $20 inspection fee and remitted all of the money to the state. The state then paid the contractor on a periodic basis a fee for each vehicle inspected according to terms set out in the contract.

The new system is decentralized. Instead of 25 test sites owned and operated by a single entity, the system consists of about 300 locations, 50 of which are equipped to perform tests on diesel-powered vehicles. Each of the 300 locations is a DMV-licensed dealer or repairer that has been recruited to participate in the inspection system. Instead of performing the inspections itself, the state's contractor oversees the system of inspection sites. It provides the equipment used to test the vehicles to each of the inspection facilities and charges them a monthly maintenance fee and for materials used. The contractor was responsible for training the inspectors who would be performing the actual inspections. Among other things, the state's contractor must monitor the system, discipline facilities that do not perform according to program specifications, and assure that facilities that leave the system are replaced by others to maintain the full compliment of inspection locations called for in the contract.

The inspection fee under the new system remained at $20. But instead of the money being remitted to the state for redistribution, it is kept by the inspection facility. Under the terms of the agreements signed by the inspection facility and the contractor, the inspection facility keeps $12.50 of the $20 fee and remits the other $7.50 to the contractor.


Non-Diesel-Powered Vehicles

The test procedures differ considerably between the old and new programs. Under the old program, all vehicles underwent the same type of test. A probe was inserted in the vehicle's tailpipe and the exhaust gases were sampled. If a vehicle failed this initial test, it was “conditioned” for a retest by running on a dynamometer (a vehicle treadmill) at a set speed for a specific period. This conditioning would clear out any gases that had accumulated in the vehicle's system while it was idling and waiting for its test. After the vehicle was run in this way it would be run through the test a second time and had to pass to be in compliance.

Beginning with the 1996 models, all of the motor vehicle manufacturers began designing their vehicles with built-in computer-based monitoring of major vehicle systems, including emissions control systems. In these systems, known as on-board diagnostic systems (OBD), a computer module in the vehicle collects and stores data on how the various vehicle systems are functioning. When the information in the computer is downloaded by a mechanic, various codes tell the mechanic how the systems are working and what problems may exist.

In the new emissions inspection program, the primary test procedure for 1996 and newer non-diesel vehicles is the OBD test procedure. The emissions inspection technician hooks the facility's diagnostic computer into a vehicle's OBD module and downloads data on its emissions control system. Based on the information it gets, the computer determines if the vehicle is operating in a manner that complies with the applicable emissions standards.

The OBD test is the primary test for 1996 and newer vehicles. A few vehicle models cannot be tested using OBD and in some cases, the computer connection to the vehicle's OBD system cannot be made. In these cases, there is a secondary test procedure called the Acceleration Simulation Mode or ASM 25/25. This is a tailpipe test similar to the test performed under the old emissions inspection system, but it differs in several ways. The test is performed on a dynamometer where the vehicle is run at 25% of the load required to accelerate at 3.3 mph per second at a speed of 25 mph. The vehicle's emissions are then sampled by a probe inserted in the tail pipe. The ASM 25/25 test is the primary test performed on pre-1996 model vehicles.

The third type of test is called the Pre-conditioned Two-Speed Idle test. This test is closest to the test that was given under the old program. It uses a tailpipe sensor to sample emissions at two different engine speeds, while the transmission is in neutral. The engine is run at between 2,200 and 2,800 rpm for 90 seconds and then at an idling speed of 350 to 1,100 rpm for 90 seconds. The two-speed idle test is given to full time four-wheel drive vehicles and vehicles with traction control that cannot be deactivated. These vehicles cannot be safely run on a dynamometer. It is also the primary test for all non-diesel vehicles over 8,500 pounds. These vehicles are usually too large to fit on the dynamometer.

Diesel-Powered Vehicles

A different test is used for diesel-powered vehicles that are over 8,500 pounds gross weight or are 8,500 pounds or less and model year 1996 or older. The test is called the 30 mph Steady State Opacity Test. The vehicle's exhaust is measured for compliance while it is running on the dynamometer at a constant simulated speed of 30 mph and an eight horsepower loading. The vehicle exhaust cannot have an opacity of more than 20%. (Unlike non-diesel powered vehicles where the exhaust is measured for the presence of carbon monoxide and hydrocarbons in certain amounts, diesel exhaust is analyzed for its opacity, which indicates the presence of particulates, the hazardous byproduct that is being regulated.)

If these diesel-powered vehicles cannot fit or cannot use the dynamometer for some reason the secondary test that is used is called the Modified Snap Acceleration Opacity Test. The test is performed while the vehicle is in neutral. The inspector accelerates the engine sufficiently so that the engine temperature increases and the exhaust clears. An average of several tailpipe readings is taken. The pass-fail standard is 40% opacity.


Originally, the old emissions inspection system applied to all gasoline powered motor vehicles weighing up to 10,000 pounds. Vehicles over 10,000 pounds, non-gasoline powered vehicles (primarily diesels), new vehicles for the first model year, vehicles manufactured before the 1968 model year, motorcycles, farm vehicles, and off-road vehicles were exempt. The reasons for the exemptions differed. For example, pre-1968 model vehicles were exempt because they had no emissions control equipment and inspection would have no effect on their performance. Diesel-powered vehicles were exempt both because they had no pollution control equipment and there was no test procedure available to apply to them. New vehicles were exempt for the first year because studies showed that there was little degradation in the performance of their emissions control equipment until they were at least one year old. Vehicles over 10,000 pounds were excluded because there are relatively few of them registered in Connecticut relative to vehicles under 10,000 pounds and the heavy duty equipment necessary to inspect them was more expensive and judged not to be cost beneficial.

Diesel-powered vehicles up to 10,000 pounds became subject to emissions inspections in 1993. The law was changed so that the only non-gasoline powered vehicles remaining exempt from the inspection requirements were those powered by electricity.

In 1997, exemptions were added to the law for (1) diesel-powered Type II school buses and (2) antique, rare, or special interest motor vehicles. Type II school buses are the smaller size school buses that weigh 10,000 pounds or less. Antique, rare, or special interest vehicles were defined as vehicles which were 25 years old or older and being preserved without modification from original manufacturer's specifications because of historical interest

In 1998, the exemption for pre-1968 model year vehicles was replaced by an exemption for any vehicles manufactured 25 or more years ago. Thus, beginning in 1998, any vehicle that was at least 25 years old was no longer subject to inspection under the old program. The separate exemption for antique, rare, or special interest vehicles was removed from the law in 2005.

These exemptions continue under the new emissions inspection program. In addition, any new motor vehicle is exempt from emissions inspection for its first four model years from manufacture.


The main difference between the old and new program with respect to enforcement is that the compliance stickers that had to be displayed on a vehicle's windshield have been replaced by registration-based enforcement. In the old program, the window sticker issued for a particular vehicle indicated both whether it was in compliance and when it was required to be re-inspected. Operation in violation of compliance requirements is an infraction ($75 for first offense: $92 for subsequent offense).

The new inspection system is linked to the DMV registration database. Information on a vehicle with respect to whether it has reported for its required inspection and its compliance status is provided from the inspection station computer to the DMV database in virtual real time. Information is noted in the registration record if a vehicle fails to be inspected as required or fails its inspection and does not receive a waiver from compliance, and the vehicle's registration cannot be renewed when it comes due. In 2006, DMV denied 38,759 registration renewals for noncompliance of which 34,290 subsequently complied. It remains an infraction to operate without being in compliance with emissions requirements.


Unreasonable Cost of Repair

Under the old program, a vehicle that failed its initial emissions test could be repaired and retested once without additional charge. If it failed its retest, it could qualify for a waiver from compliance based on “unreasonable cost of repair.” The early legislation setting up the old program (PA 78-335) established a $75 maximum amount, which defined “unreasonable cost of repair.” This was reduced by the legislature to $70 in 1979 and, by 1983 when the program began operating, to $40 (PA 83-561).

However, in 1989 new federal regulations took effect that set standards for states with inspection programs like the one required for Connecticut. One of these requirements affected the circumstances for granting waivers from compliance. The regulation (40 CFR Sec. 51.360), among other things, required that states with enhanced emissions inspection programs such as Connecticut's, establish a minimum cost for repairs necessary to qualify for a waiver from compliance. This had to be at least $450, adjusted annually for inflation based on the Consumer Price Index.

The legislature eliminated the $40 minimum repair cost provision from the law in 1993 (PA 93-312) and specified instead that unreasonable cost of repair meant cost in excess of the amounts required for expenditure in the federal regulation. DMV has specified these amounts since through its regulations. Thus the current $660 minimum

repair costs are based on the inflation-adjusted amount specified in federal regulation. This amount existed under the old program and was carried over into the new program.

Waiver Process

Because the legislature changed the law in 1993 to accommodate the requirements of federal regulations regarding waivers from compliance, the process has essentially spanned the old and new systems. Besides the modification of the unreasonable cost of repair standard, the legislature also added provisions to the law in 1993 that allowing for waivers based on economic hardship and for physical and functional diagnosis to determine that no further emissions-related repairs are needed on a vehicle. These provisions reflect the standards set in the federal regulations.

If a vehicle fails its initial emissions inspection, it must be repaired and can get one free re-inspection within 30 days. Although the vehicle inspection report may indicate what repairs are likely to be required, it is not absolutely accurate since failures can occur for more than one reason.

One point about which people sometimes get confused is the meaning of the unreasonable cost of repair standard. Some people mistakenly believe that if the required repair costs more than the $660 standard, it does not have to be performed. That is not the case. If the required repair costs more than the $660 minimum, it still must be performed. If after the required repair has been performed the vehicle fails again upon re-inspection, the fact that the cost of the repair exceeded the minimum repair cost standard allows the owner to meet the initial criterion for getting a waiver from compliance.

There are three types of waivers the owner of a vehicle that is repaired and fails upon re-inspection may be able to get. The first is for the owner to apply for a waiver on the required DMV form and present satisfactory evidence that the necessary repairs have been made and the costs have exceeded the threshold for unreasonable repair cost. The second is called a diagnostic waiver. The third is for the owner to apply for a waiver due to economic hardship. All of these procedures are governed by federal regulations for emissions inspection programs.

To qualify for a waiver due to unreasonable cost to repair, the owner must have had all repairs performed by a licensed repair facility that has repair technicians certified by DMV to perform emissions repairs. Any repairs made by the vehicle owner or by someone not certified to do emissions repairs cannot be counted. Expenditures for repairs must be for actual repairs made after available emissions related warranty coverage or written denial of such coverage by the vehicle manufacturer. Repairs necessary to restore emissions control equipment that has been tampered with also cannot be counted toward meeting the unreasonable cost of repair threshold. The owner must have a written receipt from the repair facility showing the repairs performed. A written estimate is not sufficient.

A vehicle owner can apply for a diagnostic waiver if a vehicle diagnosis fails to reveal any problem or there is no evidence to suggest emissions repairs are needed. The vehicle must then undergo a complete physical and functional diagnosis by DMV personnel. If the DMV inspector validates that no additional repairs are required a diagnostic waiver may be granted.

A hardship waiver is, in effect, a temporary extension of time based on a vehicle owner's inability to pay for necessary repairs due to economic status. To qualify, the person must submit an affidavit indicating either a lack of gainful employment or an annual income that is at or below state and federal poverty guidelines. The person must also submit evidence of any governmental and utility assistance programs providing him benefits, as well as the level of benefits received. Finally, he must attest that he has no other assets that can be used to pay for the necessary repairs. DMV must keep confidential all of the information it gets from someone applying for a hardship waiver. A hardship waiver only grants an extension from compliance until the next time the vehicle is scheduled to be tested.


One question that frequently arises about the OBD test procedure is the situation with respect to a vehicle reporting for inspection with the “check engine” light illuminated. These dashboard lights, known as malfunction indicator lights (MIL), are part of the OBD system and are primarily designed to alert the operator of malfunctions in one or more of the vehicle's emissions control systems that could be causing it to emit excessive pollutants. The MIL is designed to go on when sensors in the vehicle's OBD system detect any problem that causes the vehicle's hydrocarbon emissions to exceed 150% of the maximum federal standard established for manufacturers for that make and model. Depending on the make and model of vehicle, the illuminated MIL might say “Check Engine,” “Service Engine Soon,” or “Check Engine Soon.”

Usually, the problems associated with an MIL going on do not immediately affect a vehicle's driving performance, but by design they indicate a likely problem with its emissions levels. A MIL that goes on and stays on may indicate a relatively minor emissions problem, such as a faulty oxygen sensor, but if the light flashes on and off it could indicate a more serious problem, such as an engine misfire. When the MIL is triggered the vehicle OBD system stores the diagnostic trouble codes associated with the problem in the computer's memory.

The MIL is supposed to light up when the key is turned to the on position but the engine has not been started. Once the engine starts, the MIL is supposed to go off. If a vehicle inspection technician turns the key to the on position without starting the engine and the MIL does not light up, it is called a “key on, engine off” or KOEO failure. Under the federal OBD inspection procedures that the state must follow, a vehicle with a KOEO condition is considered to have failed the OBD test (40 CFR Sec. 85.2222).

If the inspection technician starts the vehicle's engine and the MIL stays lit, the vehicle is considered to have an MIL “commanded-on” condition. The inspection computer sends a signal to the vehicle's computer to determine the diagnostic trouble codes it has stored, records them in the vehicle test record and, according to the federal test procedure regulations, the vehicle fails the OBD inspection. Since the primary design feature of the MIL is to illuminate when problems with emissions control features of the vehicle cause it to exceed the maximum hydrocarbon levels specified for it, the basic rationale for it failing the OBD test is that its onboard diagnostic system has already detected problems that may need to be addressed before it can pass inspection.

In 2006, almost 65% of the 758,752 vehicles receiving their initial emissions inspections underwent the OBD test procedure. Of the OBD-tested vehicles, 36,298 (7%) failed their initial test. According to the data compiled by the state's consultant for assessing the program's performance, over 85% of all of the OBD test failures are because of MIL commanded-on failures.