OBD-ii (page 3 of 3)

On 28th May 1997, the EPA proposed changes to the federal OBD requirements for implementation beginning with the 1999 model year. These revisions included:

• harmonizing the emission levels above which a component or system is considered

malfunctioning with those of CARB OBD-II requirements

• mandating that federal OBD systems fully evaluate the entire emission control system

including the evaporative emission control system

• indefinately extending the allowance of deficiencies for federal OBD vehicles
• indefinately extending the allowance of optional compliance with the CARB OBD-II

requirements

• providing flexibility for alternate fuelled vehicles through 2004 MY rather than only through

1998 MY

• updating recommended practices by the Society of Automotive Engineers (SAE)
• incorporating two standardization protocols developed by the International Organization for

Standardization (ISO)

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: 1. Catalyst deterioration or malfunction before it results in an increase in HC emissions equal to or greater than 1.5 times the HC standard. 2. Engine misfire before it results in an exhaust emission exceedance of 1.5 times the applicable standard for HC, CO or NO_x. 3. Oxygen sensor deterioration or malfunction before it results in an exhaust emission exceedance of 1.5 times the applicable standard for HC, CO or NO_x. 4. Any vapour leak in the evaporative and/or refueling system (excluding the tubing and connections between the purge valve and the intake manifold) greater than or equal in magnitude to a leak caused by a 0.040 inch diameter orifice. 5. Deterioration or malfunction occurring in a powertrain system or component directly intended to control emissions including (where applicable):

• Exhaust Gas Recirculation (EGR) System
• Secondary Air Injection (SAI) System
• Fuel control system

Failure is applicable if the resulting exhaust emissions eceed 1.5 times the applicable emission standard for HC, CO or NO_x. 6. Any other deterioration or malfunction occurring in an electronic emission-related powertrain system or component that either provides input to or receives commands from the on-board computer and has a measurable impact on emissions. Monitoring of components will be satisfied by:

• electrical circuit continuity checks
• rationality checks for computer input components (input values within manufacturer

specified ranges)

• functionality checks for computer output components (proper functional response to

computer commands) 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 malfunction indicator light (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.