From model year 1996, vehicles manufactured for the North American market are equipped with a Government required diagnostic system known as On-Board Diagnostics II (OBD II). This system monitors operation and function of all engine management system activity and automatic transmission operation to insure compliance with specified emission levels.

Vehicle emission levels are constantly monitored by the OBD II system and malfunctions are recognized and recorded. A Malfunction Indicator Light (MIL) in the instrument cluster alerts the driver to the fault and the need to have the system checked for fault codes. These codes follow a standard format and are known as Diagnostic Trouble Codes (DTCs).

DTCs are assigned two codes. The first code is a numerical code assigned by the factory. The second code is referred to as a P-code and follows a structure required by law and defined by the Society of Automotive Engineers (SAE). This standard uses a letter to designate the system and four numbers to further identify and detail the malfunction as listed below.

Trouble Codes part I

Trouble Codes part II

Trouble Codes part III

Trouble Codes part IV

This is about a 35 page table. You may want to search for the DTC you need using your browser's "find" feature. (Often this is under the 'edit' menu / 'find', in Internet Explorer, also use Ctrl+F).

First digit structure is as follows:

• Pxxxx for powertrain
• Bxxxx for body
• Cxxxx for chassis
• Uxxxx for future systems

Second digit structure is:

• P0xxx Government required codes
• P1xxx Manufacturer codes for additional emission system function; not required but reported to the government

Third digit structure is:

• Px1xx measurement of air and fuel
• Px2xx measurement of air and fuel
• Px3xx ignition system
• Px4xx additional emission control
• Px5xx speed and idle regulation
• Px6xx computer and output signals
• Px7xx transmission
• Px8xx transmission
• Px9xx control modules, input and output signals

The fourth and fifth digits designate the individual components and systems.

Audi Diagnostic Trouble Codes (DTCs) and data can be retrieved with VW/Audi Factory Scan Tools such as the VAG 1551, VAG 1552, or the new diagnostic computer VAS 5051 through a Data Link Connector (DLC). For location of the data link connector, see Maintenance section. Several aftermarket scan tools and computer programs are also capable of retrieving this information in this factory mode. The factory mode also allows the scan tool to be used for other system diagnostic functions and information retrieval.

Some DTC information can also be retrieved in a generic mode. The generic mode is not as complete as the factory mode, but allows commercially available scan tools to be used simply to read DTCs. Generic scan tool mode does not have the capability to retrieve the detailed information of a manufacturer-specific scan tool.