The MIL is typically the "Check Engine" light on the instrument panel. The MIL alerts the vehicle owner that there is a problem and that the vehicle should be brought in for service. The service technician can read the fault code from the OBDII computer to help determine what repairs are required.
OBDII converters are catalytic converters that have been installed on vehicles with the OBDII monitoring system.
All 1996 and newer passenger cars and light trucks are OBDII vehicles. Some 1994 and 1995 vehicles also have an OBDII system, because the implementation of the law was phased in over.
The most reliable way to identify whether or not a vehicle is an OBDII vehicle is by visual inspection of the exhaust system. If there is an oxygen sensor installed anywhere downstream of a catalytic converter, then it is an OBDII vehicle. Some manufacturers state whether a vehicle is OBDII compliant on the emissions label located in the engine compartment.
The OBDII system is required to monitor the catalytic converter to ensure that the tailpipe emissions do not exceed the legal limits. Unfortunately, there is no current emission sensor technology available that can be installed on a vehicle to monitor tailpipe pollutant levels. Instead, vehicle manufacturers use an oxygen sensor to indirectly estimate whether or not a catalytic converter is functioning properly.
Since emission levels are estimated rather than being measured directly, it is theoretically possible to produce a catalytic converter which meets emission standards yet also shows a "check engine" light on the instrument panel.
Therefore, government policy needs to ensure that aftermarket catalytic converters are compatible with the vehicle's OBDII system, in addition to meeting emission requirements. The United States Environmental Protection Agency and the California Air Resources Board have implemented policies to address this issue. However, they have taken two different approaches to the problem.
Obviously, this is a relatively complicated set of parameters for a repair technician to consider when trying to decide which converter to install on a vehicle. As a result, California OBDII converters may not be selected simply by referring to a vehicle engine size and weight. The California Air Resources Board requires OBDII converters to cataloged specifically by vehicle make, model, engine, and any further description needed to precisely characterize an approved vehicle application. Repair technicians may only install the converter that is cataloged for the vehicle, and may not install a converter on any vehicle that is not listed.
Converters are designed to meet California OBDII requirements. A
separate application guide is available which lists California approved vehicle
California OBDII converter performance requires more active catalyst with larger, more heavily loaded bricks and higher temperature durability to meet the standards. As a result, they have a significantly enhanced environmental impact versus standard aftermarket converters.
This enhanced performance provides an excellent option for environmentally conscious individuals who would like to use CleanAir Ultra converters on pre-OBDII vehicles, or in the other 49 states, instead of using the cheapest (and less "green") part available. The performance enhancement of a CleanAir Ultra converter versus a standard converter is readily observable in I/M test lanes in side-by-side test comparisons.