The development of OBD can be appreciated by consideration of the associated legislation and the recommendations of the controlling bodies that have brought about its introduction.
Limitations on the quantities of pollutants that are deemed acceptable are becoming ever more stringent and differs in accordance with the relevant market legislation in force. The limitations prescribed by the California Environmental Protection Agency (CAL EPA) and its policy implementing arm, the California Air Resources Board (CARB) have air-quality programs that have led the way with regards to emissions legislation for quite some time. These measures are usually adopted at a later date by other emission control authorities around the world, and an analysis of the measures imposed by CARB are a good indication of what to expect in other markets.
To achieve clean air, CARB develops increasingly stringent emission standards for motor vehicles, transportation control measures, improvements to consumer products and specifications for cleaner fuels.
The Environmental Protection Agency (EPA) is responsible for the drafting and implementation of legislation relating to vehicle emissions in the United States of America. In many cases, the EPA has adopted the CARB regulations with some minor modifications. Specifically, the EPA has responsibility for:
The origins of OBDII actually date back to 1982 in California, when CARB began developing regulations requiring all vehicles sold in the State from 1988 to have an On-Board diagnostic system (OBD1). OBD1 was relatively simple and only monitored the oxygen sensor, EGR system, fuel delivery system and engine control module.
The essential functionality for OBD1 systems was that the engine management system monitors all electrical components that affect exhaust emissions and provide an optical warning signal in the event of a relevant malfunction. The corresponding fault could be read via a flashing code without the aid of a testing device. Usually the display method was an LED on the ECM or the equivalent of a Malfunction Indicator Lamp (MIL) in the instrument pack. The technician would have to count the number of flashes of the MIL to decipher the displayed code.
OBD1 did not provide guidelines or legislation to provide standardization between different vehicle manufacturers or vehicle models. Consequently, different adapters were needed to work on different vehicles and some systems could only be accessed using dealer specific scan tools.
Another limitation of OBD1 was that it couldn't detect certain kinds of problems such as a non-functioning or missing catalytic converter, ignition misfires, or evaporative emission problems. In addition, the MIL would only illuminate after a failure had occurred, it had no way of monitoring progressive deterioration of emissions-related components.
CARB proposed a new set of standards for an enhanced OBD system in 1989 that were incorporated into the federal Clean Air Act of 1990. In 1994, the US EPA and CARB issued this strict new set of guidelines and a phase-in program concerning the application of On-Board Diagnostics systems began; this was to be mandatory for certain passenger vehicles. These guidelines known as OBDII were designed to detect emissions-systems related malfunctions and facilitate their repair before vehicle performance could deteriorate.
The MIL on OBDII systems is set to illuminate any time a vehicle's hydrocarbon (HC), carbon monoxide (CO), oxides of nitrogen (NOx) or evaporative emissions exceed 1.5 times the Federal Test Procedure (FTP) standards for that model year of vehicle.
This includes:
For diesel systems - any time a fault in the EGR system causes NOx emissions to rise. Therefore, the MIL may illuminate even though the vehicle seems to be running normally and there are no apparent drivability problems. Because a vehicle may appear to be running well even though the emission levels have increased due to a system or component fault, the MIL provides a means of alerting the driver of the vehicle that they are causing pollution and they need to get their emissions problems fixed.
Because motorists may ignore the MIL even when it is indicating a fault, regulators want to incorporate OBDII into existing and enhanced vehicle emissions inspection programs. If the MIL is found to be on when a vehicle is tested, it will not pass the tests even if the exhaust pipe emissions are within acceptable limits.
Another important development of OBDII over OBD1 was the introduction of defined standards for trouble codes and diagnostic equipment. The Air Resources Board required that all manufacturers must conform to standards for the following:
In 1996, the phase-in period for vehicles in California was to be completed and the scope of the OBDII regulations was expanded to apply to all passenger cars in the US market (i.e. since 1st January 1996 all cars built for the US market have OBDII systems).
Although some manufacturers started incorporating OBDII in various models as early as 1994, some of the earlier OBDII cars were not 100% compliant.
In addition to more advanced software, OBDII systems typically include the following features over and above that used on OBDI systems:
Standardization is an important part of the OBD regulations and it facilitates for access to emission-related trouble codes, emission-related powertrain test information (i.e., parameter values), emission related diagnostic procedures, and stored freeze frame data based on industry specifications.
Standardization of the message content (including test modes and test messages) as well as standardization of the downloading protocol for fault codes, parameter values and their units, and freeze frame data are specified in SAE recommended practices "OBDII Scan Tool" (J1978) which was issued in June 1994, and "E/E Diagnostic Test Modes" (J1979) which was issued in July 1996. Fault codes, parameter values, and freeze frame data have to be capable of being downloaded to a generic scan tool that meets these SAE specifications.
Despite the move towards standardization, there are three basic OBDII protocols in use in the US market. Each of the protocols has minor variations on the communication pattern between the onboard diagnostic computer and the scan tool. Chrysler products, all European models and most Asian imports use ISO 9141 circuitry, General Motor cars and light trucks use SAE J1850 Variable Pulse Width Modulation (VPW) and Fords use SAE J1850 Pulse Width Modulation (PWM) communication patterns. These differences are reflected in the pin numbers used for diagnostic communication on the diagnostic connector. Even though there are three OBDII electrical connection protocols, the command set is fixed according to the SAE J1979 standard.
Other SAE standards relating to OBDII include:
On 28th May 1997, the EPA proposed changes to the federal OBD requirements for implementation beginning with the 1999 model year. These revisions included:
Beginning in the 1999 model year, OBD systems on spark-ignition cars must be able to detect and alert the driver of the following emission-related malfunctions:
Failure is applicable if the resulting exhaust emissions exceed 1.5 times the applicable emission standard for HC, CO or NOx.
Malfunctions are defined as a failure of the system or component to meet the electrical circuit continuity checks or the rationality or functionality checks.
Upon detection of a malfunction, the MIL is to be illuminated and a fault code stored no later than the end of the next driving cycle during which monitoring occurs, provided the malfunction is again detected.
The OBDII standards have now been adopted by the European community and developed for the European automotive sector for compulsory implementation in 2000MY.
The European Parliament has issued its own directive aimed at reducing pollution from motor vehicles which is commonly known as 'EURO-3', and is a development of the earlier EU-1 and EU-2 regulations.
In addition to lower emission limits, the directive also covers the monitoring of emission-related components and functions during operation, based on the US OBDII model.
If an emissions related fault is diagnosed by the engine management system, which results in a significant increase in the vehicle emissions, a MIL must be illuminated to inform the driver that the vehicle needs to be checked for emission-related faults.
For petrol-engine passenger cars up to a total weight of 2500 kg the following maximum pollutant limits have been set by the EURO-3 legislation:
EOBD stipulates the monitoring of the functions of the following systems:
The Engine Management System (EMS) ECM monitors the above systems by checking the data from different sensors fitted to the vehicle and the associated data records stored in internal memory (memory mapping) to monitor environmental conditions and engine operation.
Default values for some components are stored in system memory, which the ECM uses if it cannot determine the environmental or engine operating conditions due to a faulty signal. If a faulty sensor is detected, the MIL is illuminated when the fault has been confirmed over the relevant number of drive cycles.
The relevant market authorities such as the European Parliament are responsible for introducing legislation designed to reduce emissions from motor vehicles. The aim of this legislation is to protect the environment in accordance with internationally set targets and agreements.
OBDII legislation requires all vehicle manufacturers to provide detailed information on all emission related diagnostic trouble codes (P-codes) caused by faults in the engine management system and any other systems likely to have an effect on vehicle emissions. The emission effect threshold is an increase of 1.5 times that of the base vehicle standard.
The operational reliability of the exhaust treatment system must be guaranteed for 5 years and/or 100,000 miles. The data relevant to exhaust emissions are read out via a standardized interface using a diagnostic tool such as 'OmiScan' or 'OmiCheck'.
If a violation of the OBD system is identified, the vehicle manufacturer is legally bound to eliminate the fault throughout the entire vehicle series.
The European Commission and its Council for the environment is responsible for the drafting and implementation of legislation concerned with protection of the environment. This includes the setting of limits for the level of permissible emissions from road transport across all Member States in the European Union.
In order to set realistic and achievable goals for pollutant limitation, the Commission works in co-operation with a number of bodies such as ACEA (European Automobile Manufacturers' Association).
In many cases, the European Commission has had the advantage of being able to learn from the introduction of emission control measures imposed through legislation set by CARB in California.
As from 2000MY, this has include the mandatory introduction of OBD systems on new vehicles sold within the European Union.
The first item of legislation to set specific limits for the emission of certain pollutants from motor vehicles in the European Union was Directive 70/220/EC. This Directive has been regularly updated since its introduction, up to the present date, whereby Directive 98/69/EC is used to amend Directive 70/220/EC to include the OBD requirements.
The following information highlights some of the Directives issued through European Union legislation and demonstrates the progressive tightening of emissions standards, a trend that can be expected to continue for the foreseeable future. This includes a commitment to the introduction of On-Board Diagnostics systems.
The first programme of action of the European Community with regards to emissions from motor vehicles was established 22nd November 1973. This directive called for scientific advances in technology to be adopted to tackle the problem as and when it became available. This has been amended and updated over time by further resolutions. The Council in its Resolution of 1st February 1993 approved the fifth programme of action.
This called for additional efforts to be made for a considerable reduction in the then present levels of emissions of pollutants from motor vehicles and also set targets in terms of emission reductions for various pollutants.
Council Directive 70/220/EC (20th March 1970) laid down the limit values for carbon monoxide and non-burnt hydrocarbon emissions from vehicle engines and these limits were further reduced by Council Directive 74/290/EC (28th May 1974). This was supplemented with Commission Directive 77/102/EC (30th November 1976) which imposed limit values for permissible emissions of nitrogen oxides. Limit values for all three types of pollution were successively reduced by Commission Directive 78/665/EC (14th July 1978) and Council Directives 83/351/EC (16th June 1983) and 88/76/EC (3rd December 1987).
Council Directive 88/436/EC (16th June 1988) introduced limit values for particulate emissions from diesel engines.
Council Directive 88/458/EC (18th July 1989) introduced more stringent European standards for emissions of gaseous pollutants from motor vehicles below 1400 cm3. This standard was extended to all passenger cars independently of their engine capacity on the basis of an improved European test procedure comprising an extra-urban driving cycle.
Council Directive 91/441/EC (26th June 1991) introduced requirements relating to evaporative emissions and to the durability of emission-related vehicle components, as well as more stringent particulate pollutant standards for motor vehicles equipped with diesel engines.
Passenger cars designed to carry more than six occupants and having a maximum mass of more than 2500 kg, light commercial vehicles and off-road vehicles were previously covered by Directive 70/220/EC which benefited from less stringent standards. These were superseded by Council Directive 93/59/EC (28th June 1993) and Directive 96/69/EC (8th October 1996) of the European Parliament and of the Council which impose standards as stringent as the respective standards for passenger cars, taking into account the specific conditions of these vehicles.
Directive 94/12/EC (23rd March 1994) of the European Parliament and Council introduced more stringent limit values for all pollutants and a new method for checking on the conformity of production.
In the course of its efforts to improve air quality, the European Parliament and Council issued the 'Directive 98/69/EC (13th October 1998) on Measures to Counter the Pollution of Air by Emissions from Motor Vehicles'. The directive, published on 28/12/98, had an immediate impact on car manufacturers. The stipulations laid down in the directive had to be satisfied within specific time limits for all new vehicles with petrol and diesel engines up to a total weight of 2.5 tonnes that are sold in the member states of the EU. The most stringent values laid down by Directive 98/69/EC, applied from 2000 and 2005 according to the type of vehicle:
The Directives apply to tailpipe emissions, evaporative emissions, emissions of crankcase gases and the durability of anti-pollution devices for all motor vehicles equipped with spark-ignition engines and to the tailpipe emissions and durability of anti-pollution devices of certain category vehicles fitted with compression-ignition engines.
Article 4 of Directive 94/12/EC required the Commission to propose standards to be enforced after the year 2000, according to a new multifaceted approach, based on a comprehensive assessment of costs and efficiency of all measures aimed at reducing road transport pollution.
These proposals included the following areas of consideration:
The proposal was based on the establishment of air quality criteria and associated emission reduction objectives, and an evaluation of the cost-effectiveness of each package of measures.
The proposal also took into account the potential contribution of other measures such as traffic management, enhancement of urban public transport, new propulsion technologies and the use of alternative fuels. Given the urgency of community action on the limitation of pollutant emissions by motor vehicles, the proposals were based on the then present or anticipated best available anti-pollution technologies that were liable to speed up the replacement of polluting motor vehicles.
The proposals stipulated the provisions for OBD should be introduced with a view to permitting an immediate detection of failure of anti-pollution vehicle equipment and thus allowing a significant upgrading of the maintenance of initial emissions performance on in-service vehicles through periodic or kerbside control. It was recognized that OBD for diesel engine vehicles was at a less developed stage and could not be fitted to all diesel vehicles until 2005.
Other measures specific to OBD include the following:
Vehicles compliant with OBDII systems legislation in force in the United States, and particularly in California, include additional emissions system controls such as Advanced EVAP systems to detect for leaks in the fuel evaporative system, and secondary air injection during cold starting. Such measures were introduced within the European Union in later legislation and led to the introduction of more sophisticated OBD systems. Proposals for these and other measures were stipulated in Directive 94/12/EC as follows:
Directive 98/69/EC dealt with motor vehicle emissions and reduced the permitted level of nitrogen oxides and total hydrocarbons by 40%. The directive also laid down new mandatory limit values for carbon monoxide and particulate emissions from passenger cars and light commercial vehicles fitted with petrol or diesel engines. New vehicles had to meet the directive limit values with effect from 1st January 2000 in order to be granted EC or national type-approval.
The Directive's new limit values entailed large investments from the EU car industry in research and development of new technologies. The requirements also introduced new mandatory legislation for petrol vehicles to be equipped with an On-Board Diagnostic System from 2000 MY and diesel vehicles to be equipped with OBD systems from 2003MY.
Significant extracts from Directive 98/69/EC of the European Parliament and of the Council of 13th October 1998 relating to measures to be taken against air pollution by emissions from motor vehicles and amending Council Directive 70/220/EC are reproduced below:
Further developments, which had an impact on after sales service in direct relation to OBD, included the following proposals:
When drawing up these proposals, the Commission had to take account of several factors:
Directive 98/69/EC also provided, where appropriate, for the drafting of standards concerning the component approval of vehicles using alternative power plants or fuels.
Member States may introduce tax or financial incentives for the re-equipment of in-use vehicles to meet the values laid down in Directive 98/69/EC or previous amendments to Directive 70/220/EC, and for laying up vehicles that do not comply.
The Directives lay down differing limit values for emissions by petrol and diesel cars:
Tax incentives can be granted by Member states to encourage the advance compliance with new limit values. These incentives are permitted on the following conditions:
The procedure for the component-approval of vehicles includes:
Up to 28th September 1999, the full European test cycle provided for by Directive 91/441/EC was used as the testing procedure in order to establish compliance with the limit values. After that date the test procedure introduced by Directive 89/69/EC applied.
The EC Directives included explanations of the scope of the legislation and the terms used:
To date, the European legislation relating to vehicle emissions has introduced specifications for six specific emissions tests:
The 98/69/EC directive defines the OBD requirements and tests as follows:
In satisfying the requirements of Directive 98/69/EC, the OBD system must, at a minimum, monitor for:
For both positive-ignition and compression ignition vehicles, the sequence of diagnostic checks must be initiated at each engine start and completed at least once provided that the correct test conditions are met. The test conditions must be selected in such a way that they all occur under normal driving as represented in the Type I test.
Directive 98/69/EC also establishes the test requirements for vehicles with compression engines. The OBD system must monitor:
With regards activation of the MIL, Directive 98/69/EC specifies the operational requirements as follows:
With regards extinguishing a MIL, the directive specifies the following requirements:
Directive 98/69/EC specifies the following requirements for OBD fault code storage:
The specifications for erasing a fault code are listed below:
In order to assure that OBD systems fitted to a manufacturer's vehicles are compliant with directive 98/69/EC, the OBD systems have to be tested according to test procedures specified within the directive. The procedure describes a method for checking the function of the on-board diagnostic (OBD) system installed on the vehicle by failure simulation of relevant systems in the engine management or emission control system. It also sets procedures for determining the durability of OBD systems.
The manufacturer must make available the defective components and/or electrical devices that are used to simulate failures. When measured over the Type I test cycle, such defective components or devices must not cause the vehicle emissions to exceed the specified limits by more than 20%.
When the vehicle is tested with the defective component or device fitted, the OBD system is approved if the MIL is activated.
The testing of OBD systems consists of the following phases:
Vehicles powered by internal combustion engines produce by-products in the form of emissions, some of which are harmful to the environment. The main by-products that are produced are water (H2O) and Carbon Dioxide (CO2). In addition, relatively low concentrations of the following potentially harmful substances are produced:
The approximate proportions of exhaust gas constituents for modern petrol vehicles is listed below:
Carbon Monoxide (CO) is a colourless, odourless gas, which is formed when hydrocarbon fuels are burnt in the combustion process and is a result of incomplete combustion.
Spark-ignition engines are particularly responsible for carbon monoxide emissions; an air/fuel mixture, which is rich in fuel, produces an excessive concentration of CO. It is important that vehicles with petrol engines are correctly tuned and maintained to provide the optimum air/fuel mixture and so ensure that carbon monoxide emissions are minimized.
In comparison, diesel engines are lean running, so tend to produce less CO emissions than equivalent petrol engines. However, if there is not enough excess air in the combustion chamber, increased emissions of carbon monoxide will result, as well as higher concentrations of soot and hydrocarbons (HC).
According to a 1997 study "Improving air quality in Europe" conducted by the Club de Bruxelles in 1996, road transport produced 65% of carbon monoxide emissions. Carbon monoxide has a significant impact on human health, in particular on the body's ability to absorb oxygen.
WARNING: Carbon monoxide is dangerous to inhale and is potentially lethal. Concentrations are particularly high when an engine is running in a workshop or other confined space.
Present in exhaust gases and like carbon monoxide, are a result of unburned fuel during combustion. HC concentrations increase as the air/fuel mixture becomes rich and also increase if a misfire occurs. Hydrocarbons are particularly prevalent when an engine is cold and are evident by the presence of white or blue smoke from the exhaust. Hydrocarbons are also produced in the crankcase in the form of vaporized lubrication oil and through evaporation of fuel from the fuel tank and fuel system.
Diesel fuels contain a large number of hydrocarbons, which have boiling points between about 180°C and 360°C and the required ignition temperature for diesel fuel is approximately 220°C. It is difficult to ensure a high enough ignition temperature for cold engines and at low speeds that have a corresponding low final compression pressure. Consequently the presence of hydrocarbons is predominant at cold starting.
Carbon Dioxide (CO2) is a by-product of complete combustion and contributes to the 'greenhouse effect', the principal cause of global warming. Carbon Dioxide is produced even under perfect combustion conditions. According to Society of Motor Manufacturers and Traders (SMMT) figures, the global warming attributable to vehicular CO2 emissions is 12% in the UK.
However, according to a 1997 study "Improving air quality in Europe" conducted by the Club de Bruxelles in 1996, road traffic produced some 80% of total carbon dioxide (CO2).
One of the conclusions reached by the European Union Council for the Environment on the 25th June 1996 was an agreement for a Community strategy to reduce CO2 emissions from passenger cars and the improvement of fuel economy to reduce the average CO2 emissions of newly registered passenger cars to 120g of CO2 per kilometre by 2005 or 2010 at the latest.
A voluntary agreement between the European Commission and the European Automobile Manufacturers' Association (ACEA) under the 'Auto-Oil Programme' in 1999, included the commitment to achieve an emission target of 140g of CO2 per kilometre for the average of the new car sales by ACEA members in the EU by 2008 and 120g/km by 2012. Japanese and Korean associations of automotive manufacturers (JAMA and KAMA) are negotiating with the Commission to conclude environmental agreements equivalent to that agreed to by ACEA.
Although these voluntary measures require additional investments in technology by the manufacturers (e.g. improved combustion engines, new means of propulsion etc.), these costs are justified on the grounds of protection of human health and the environment.
In order to achieve its objectives with regards the limitation of CO2 emissions, the Commission is proposing monitoring of CO2 emissions from new passenger cars registered in a given calendar year as well as information on the manufacturer, fuel type, mass, engine power and engine capacity.
In addition, the Council has reached a political agreement that will make it mandatory for the consumer to be supplied with information concerning fuel consumption and the CO2 emissions of new cars. The customer can then use the comparable information from different manufacturers and vehicles before making a purchase decision. The aim of this is to influence consumer choice in favour of more fuel efficient and environmentally friendly cars. The following sources of information would have to be made available to customers:
Includes Nitric Oxide (NO) and Nitrogen Dioxide (NO2) and is produced in exhaust gases as a by-product of the combustion process. Lean mixtures produce more oxides of nitrogen than rich mixtures as the combustion temperature is increased.
According to the 1997 study, road transport is responsible for over half of all NO2 emissions. NO2 causes respiratory illnesses and damage to lung tissue and contributes to acid rain and smog. It also corrodes stone buildings, statues and monuments.
Along with sulphuric acid (H2SO4) and Oxides of Nitrogen, contribute to the formation of 'acid rain'.
It is one of the main atmospheric acidifiers and is the main culprit in the gradual erosion of buildings and other monuments of cultural heritage exposed to ambient air.
Soot Particles (diesel vehicles)
Tiny particles of carbon are produced which can carry fuel and oil. The start of injection influences the emission of soot particles; if the start of injection is delayed such that there is incomplete combustion, increased levels of soot particles will result. The use of high injection pressures, particularly at low engine speeds can greatly reduce soot emissions and optimum injection direction help to limit black smoke production.
Growing concern has been attracted by the emissions of particulate matter, since it is composed of tiny particles which can linger in the lungs with serious health effects, including cancer.
In addition to the pollutants described previously, the transport sector produces a substantial share (about 30%) of emissions of non-methane volatile organic compounds (VOC) in Europe.
Other air pollutants of concern come from substances in petrol such as lead and benzene that are also considered to be carcinogenic.
The European Commission proposes to limit benzene values from 1st January 2010 and carbon monoxide levels from 1st January 2005. The two pollutants have been exempt from controls so far, but have been linked to an increased risk of leukaemia and heart disease.
Motor vehicle emissions also create concentrations of ozone at ground level which, when exposed to heat, form the type of pollution known as "summer smog". Ozone causes breathing problems, reduced lung function, asthma, eye irritation, nasal congestion and reduced resistance to colds and other infections. Ozone can be especially dangerous for the young and the elderly, and can also damage plants and trees and cause deterioration of rubber and fabrics.
From an emissions perspective, it is extremely important that vehicles are properly maintained. It is estimated that approximately 50% of vehicle pollution is attributable to the 10% of vehicles that are badly maintained or worn out.
Car manufacturers are investing substantial sums in Research and Development in order to produce 'cleaner' more environmentally friendly engines. The emissions produced by SI engines are to a large extent dependent on engine design, power output and working load. By precisely controlling ignition timing and optimising the air/fuel ratio in the combustion chambers under all prevailing conditions, the emission levels encountered can be minimised before supplementary emission control systems need to be employed. The Engine Control Module (ECM) is primarily responsible for ensuring the optimum engine operating conditions. This is achieved by constant monitoring of all variable factors using periphery sensors and utilizing an internal memory map to determine the optimum ignition and fuelling characteristics to be delivered at any instance in time.
By supplementing these design and control measures through the utilization of additional emission control equipment, pollutant levels can be maintained below the legislated maximum levels.
The introduction of the compulsory fitting of catalytic converters has resulted in a dramatic improvement in emissions produced by cars. The Society of Motor Manufacturers and Traders (SMMT) estimate that cars fitted with catalytic converters in comparison with pre-1993 cars produce less than 10% toxic gases.
Some areas of design related improvements to CO2 emissions are sometimes offset by improvements in other areas of vehicle performance, such as safety, noise and emissions legislation and by customer demand for additional features as standard, such as air conditioning and power assisted steering.
Although these voluntary measures require additional investments in technology by the manufacturers (e.g. improved combustion engines, new means of propulsion etc.), these costs are justified on the grounds of protection of human health and the environment.
In order to achieve its objectives with regards the limitation of CO2 emissions, the Commission is proposing monitoring of CO2 emissions from new passenger cars registered in a given calendar year as well as information on the manufacturer, fuel type, mass, engine power and engine capacity.
Continuing reductions in new car emissions reaching 95% have already been achieved by the motor industry. In order to achieve significant further reductions, enhanced fuel quality will be necessary and/or the commercial acceptance of alternative power sources (e.g. electric vehicles, hydrogen fuel cells etc.).
Cleaner fuel is an essential factor in improving ambient air quality, by reducing the level of particulates produced, and improving the performance of catalytic converters. Some engine developments aimed at improving air quality cannot be introduced unless there are significant improvements in the quality of fuel.
European Commission Directive 98/70/EC tackles the issue of quality of petrol and diesel fuel and sets a time limit (2005) for the introduction of higher quality diesel and petrol including a banning of leaded petrol throughout Member States. The Directive is an outcome of the "Auto/Oil Programme", which was a joint programme initiated in 1992 between the European Commission, ACEA and EUROPIA (European oil industry). The objective of the programme is to reduce vehicle emissions and attain air quality targets through cost-effective measures that include vehicle technology, fuel quality, improved durability and other non-technical means.
Whilst both engine development and fuel quality make an important contribution to air quality, only the latter has the potential of providing an across the board effect to the entire car parc. In collaboration with government, the UK Motor Industry has undertaken an extensive programme of research into the emission of particulates from petrol and diesel engines.
With regards to OBD, poor fuel quality could cause MIL operation, a situation that has been known to occur in the United States where OBD has been used for some time. When the vehicle with the active MIL has been diagnosed, a P0300 diagnostic trouble code has been registered that would normally be associated with a lean misfire condition due to a vacuum leak, low fuel pressure, dirty injectors or an ignition problem such as fouled spark plugs, plug leads or weak ignition coils. The OBDII diagnostics treats a 2% misfire rate on an individual cylinder as normal, but water in the fuel or variations in the fuel additives in reformulated fuel can increase the misfire rate to the point where it triggers the fault code and consequent MIL operation.
The lowering of permitted emission levels from vehicles is being made progressively more stringent and the trend is set to continue for the foreseeable future until zero or near zero emission levels can be attained. In California, Low Emission Vehicles (LEVs) are already compulsory, whereby a percentage of all vehicles sold by a manufacturer must be low emission types.
From 1991 through to 1995, the state of California offered an income tax credit to individuals and businesses for the partial costs of purchasing or converting standard fuel vehicles to low emission vehicles.
Pursuant to State law, the CARB in 1990 adopted LEV and clean fuels regulations. The regulations establish an annual, increasingly stringent, average emission standard that auto manufacturers must meet for their fleet of light-duty vehicles that are available for sale in California. These regulations do not specify the type of fuel to be used by the vehicles and do not require automotive manufacturers to produce alternative-fuelled vehicles. The manufacturers may produce any combination of vehicles (LEVS, alternative-fuel vehicles etc.) as long as the average of the emissions out of the tailpipe do not exceed the mandated average emission standard for the light-duty fleet as a whole.
In addition, CARB has separate regulations dealing with the mandatory production of Ultra Low Emission Vehicles (ULEVs) and Zero-Emission Vehicles (ZEVs) such as electric powered vehicles. Originally, 2% of large auto manufacturer's fleets for sale in California were required to be ZEV type in 1998, with the proportion increasing to 5% in 2001 and 10% in 2003. This legislation was later amended, to scrap the initial targets, but the 10% requirement by 2003 is still currently in place.
