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Overview of On-Board Diagnostic Systems Used on 1991 California Vehicles
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English
Abstract
The California Air Resources Board requires that new California vehicles be equipped with on-board diagnostic (OBD) systems. Starting with the 1988 models, these systems were required on new passenger cars, light-duty trucks and medium-duty vehicles equipped with three-way catalysts and feed-back fuel controls. The purpose of the OBD system is to expedite the proper repair of emission-related malfunctions and, thus, reduce vehicle emissions. When malfunctons are detected, a malfunction indicator light (MIL) mounted in the dash panel illuminates cautioning the vehicle operator that a repair is needed. Also, a fault code is stored in the OBD computer memory. When the vehicle is brought to a repair facility, the fault code provides the mechanic with the likely areas of malfunction for repairing the vehicle. After the repair is performed, the fault code is cleared, the MIL is extinguished, and the OBD system will subsequently confirm if the proper repair has been performed. The minimum OBD criteria include monitoring of the engine's powertrain control module, fuel metering system, exhaust gas recirculation, and other emission-related systems. The OBD techniques used to monitor each system vary. This report summarizes the OBD designs used on most 1991 California models.
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Citation
Bogdanoff, M. and Hada, S., "Overview of On-Board Diagnostic Systems Used on 1991 California Vehicles," SAE Technical Paper 912433, 1991, https://doi.org/10.4271/912433.Also In
References
- Malfunction and Diagnostic System for 1988 and Subsequent Model-Year Passenger Cars, Light-Duty Trucks, and Medium-Duty Vehicles with Three-way Catalyst Systems and Feedback Control California Code of Regulations
- Overview of On-Board Diagnostic Systems Used on 1991 California Vehicles August 1990 Air Resources Board, Mobile Source Division
- Malfunction and Diagnostic System Requirements--1994 and Subsequent Model-Year Passenger Cars, Light-Duty Trucks, and Medium-Duty Vehicles with Feedback Fuel Control Systems California Code of Regulations