Diagnostic Trouble Codes (DTC) — General

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.

Earlier cars. Volkswagens and Audis of 1990–1995 carry the first-generation on-board diagnostics (OBD I), whose codes are different from the OBD II P-codes answered here. For those cars the Volkswagen Scan Tool Companion 1990–1995 is the reference. Not sure which era? A car sold in North America from model year 1996 is OBD II.

How a P-code is built → the letter and four digits, decoded.

How to connect a scan tool → factory mode, generic mode, and what each can read.

Note — the codes answered here are the scan tool codes for all Volkswagen and Audi vehicles available at the time of publication. Not all of the codes apply to any one vehicle.