On Board Diagnostics (OBD II) Overview

On Board Diagnostics (OBD II) Overview:

The OBD-II system expands the on-board monitoring and diagnostic capabilities of emission related components. The number of fault codes and related diagnostic information will be expanded.

The laws governing OBD-II require that all manufacturers install a read out connector. in the vehicle, that can be accessed using a scan tool. The law is specific as to the location, design and number of pins on the scan tool connector. The connector in the Z3 is located in the center console through an access panel located on the passenger's side.

The law also provides for standardization of terminology and fault code numbering for all manufacturers. This means that whatever make of vehicle is accessed through the scan tool will give the same codes for each type of emission related fault.

This scan tool connector and fault code readout will not affect the diagnostic procedures, for BMWs, that are accessed through the DIS Tester or MoDiC.

The number and total scope of emission monitoring will increase. However, the troubleshooting procedures and fault explanations will continue to follow the format developed for the BMW testers.

The OBD-II standards have required the manufacturers to expand and improve the self monitoring capabilities of the powertrain control modules. These changes will be reflected in the design of the engine control systems as evidenced in the DME M5.2 system. The changing requirements will also expand the fault troubleshooting and diagnostic procedures found on the DIS Tester and MoDiC.

The current list of QED-II requirements is extensive and will likely continue to grow and change. There are currently provisions for over 200 separate fault codes that relate to the powertrain systems. All of these codes will be accessible through the scan tool for any make or model vehicle.

The codes are very specific, for example there are 37 codes that relate to oxygen sensor circuit malfunctions. The following list is an example of what the control modules will monitor for compliance with OBD-II and I/M 240:
- Input and output oxygen content of the catalytic converter
- Engine for indications of misfire. The misfire must be identified by cylinder with the following data recorded - vehicle speed, engine RPM, load, engine temperature, integrator values and oxygen sensor closed/open loop operation.
- The vehicles purge system must be monitored for leaks or malfunctions at least once for every start/stop.
- The fuel delivery system must be monitored for its ability to comply with emission standards.
- The voltage and switching rate of all oxygen sensors must be monitored as well as the oxygen sensor heating.
- All other emission components and related component operation must be monitored.

Failures of any emission related components or systems will still be indicated through the check engine warning lamp in the cluster.

Each vehicle manufacturer must make emission related diagnostic and repair information available to the private repair industry. The J2008 standard calls for electronic access to this data base, possibly through CD-ROM distribution. The volume of information, for all manufacturers, prohibits any form of printed literature. The law is currently being contested by the manufacturers, who are claiming infringement on proprietary information.