Q: What Is the OBD II System on My Car?

OBD II is an abbreviation of on board diagnostic system generation two. The system was brought into service in the vehicles of model year 1996. The system was put into all vehicles to monitor the operation and control the engine and powertrain systems to meet federal and international regulations.

The computer control systems on vehicles with OBD II have the capability to allow anyone that has a scanner with the same connector to access information in the vehicle’s computer. The connector for this system is standardized for all vehicles with OBD II. The information obtained from the OBD II system using a scanner is all dependant on what information the manufacturer decides to release. A factory scanner can access all the capabilities a manufacturer releases and a generic scanner is limited to only code retrieval, but can sometimes have the capabilities of a factory scanner depending on the scanner being used.

The data that can be retrieved using a scanner is the input to the computer from the sensors in the system and the computer output to operate components after the computer has processed the input information. If the computer gets bad data or components fail, the computer will store an OBD II code in its memory. The code may be a generic code or a manufacturer specific code. The code is retrieved using the OBD II connector and a scanner. The code can be used to diagnose the vehicle problem that caused the code.

The OBD II system has a set of codes called generic codes that are used to give the general failure of a component or sensor system. The code may not give an exact component or sensor failure. This will be dependent on the manufacturer release and code meaning. The manufacturer may have additional codes they would use in addition to the OBD II generic code, called manufacturer specific codes. These codes will narrow down the diagnostics for the user further to help in diagnosis.

The OBD II system is to help in diagnosing a vehicle problem. The system was not designed to give an absolute answer to the source of the problem, but a general area for a person to look at when trying to repair the vehicle. This is why each manufacturer has a set of pinpoint tests for each code the system gives out. Some codes may or may not be used by all manufacturers. The pinpoint tests are different for all manufacturers for the same codes. This is why it is important to use the OBD II system as a guide to a repair and not just replace a part immediately. This was not its intention. It was intended to be used by a mechanic as a tool to help in diagnosing a problem with your vehicle. Today, with the advent of generic scanners it has been used as a general indication of what part to change. This has caused a large amount of repairs to be incorrect since many consumers perceive the code from the OBD II system as an indicator of what part to change. The OBD II system needs to be used again as it was intended. It is another tool to be used to help diagnose a system problem, but not a guide for the consumer to decide what parts to replace.