E-OBD

Standardization is an important part of the OBD regulations and it facilitates for access to emission-related fault 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 “OBD II 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 which meets these SAE specifications.

The OBDII standards have now been adopted by the European community and developed for the European automotive sector for compulsory implementation in 2000MY.

E-OBD

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 OBD-II model.

If an emissions related fault is diagnosed by the engine management system, which results in a significant increase in the vehicle emissions, a Malfunction Indicator Lamp (MIL) must be illuminated to inform the driver that the vehicle needs to be checked for emission-related faults.

For petrol-engined passenger cars up to a total weight of 2500 kg the following maximum pollutant limits have been set by the EURO-3 legislation:

• Carbon Monoxide (CO) – 3.2 g/km
• Hydrocarbons (HC) – 0.4 g/km
• Nitrous Oxides (NO_x) – 0.6 g/km

E-OBD stipulates the monitoring of the functions of the following systems:

• Catalytic converter
• Catalytic-converter heater (where applicable)
• Misfire detection
• Fuel system
• HO₂ sensors
• Secondary-air system (if applicable)
• Fuel filler cap captive or monitored (where applicable)

The engine management system (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 warning lamp is illuminated when the fault has been confirmed over the relevant number of drive cycles.