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VAG SCAN TOOL OPERATION: WHAT YOU NEED TO KNOW

Measuring Blocks? Controller addresses? Adaptive and Multiplicative adaption factors? These terms, and many more, are common in the Volkswagen/Audi world. This article will help explain the basics of information access on a VAG scan tool. It will show you how to find and understand VW's form of data PIDs and perform many common functions with a VAG tool. It will also explain, step by step, the Throttle Body Alignment (TBA) and kick down relearn procedures that are required after a repair or battery disconnect.

Accessing the Information

First, you ll need a scan tool with enhanced VW/Audi capabilities. In this article I will be using VCDS because it labels all of the choices we will be using. Not all scan tools label like the VCDS, and some even require manual number entry. Also VCDS, in my opinion, is the best available option for dealing with VAG vehicles. Due to its low price and extensive features, VCDS is a must have for any diagnostic technician's arsenal. Many levels of VCDS are available, however the Hex-USB+CAN Interface, for only a few hundred dollars, has exceptional coverage from 1996 model years to present. This interface should be all that most technicians need to work with VAG vehicles. VCDS can be purchased at www.ross-tech.com.

Let s start with a brief description of the VAG numbering system using VCDS.

When entering diagnostics the appropriate controller must be selected. The VAG numbering system assigns specific 2 digit numbers to each controller. PCM is 01, ABS is 03, the airbag module is 15 and so on. In this example we will choose 01 for PCM (Engine). Note how the VCDS displays each controller number next to its corresponding text label. Not all scan tools do this for you, so following the numbering system defined in the service information is critical in order to take the right path.

The next step is to choose the functions that we want to access. Again, the numbering system applies. In the image below we can see that retrieving fault codes is 02, monitor readiness status is 15, etc. Notice that freeze frame is not an option. Freeze frame has been added on the generic, or global, side to make the vehicles compliant with OBD II regulations.

Deciphering Measuring Blocks

Function 08 is measuring blocks. Measuring blocks are VAG's form of data lists. They are organized into groups of data that relate to a certain system or sub-system. Once we have selected 08 to enter measuring blocks we need to understand display groups and fields. The following screen allows for the viewing of 3 display groups of 4 fields each. The groups are chosen by the user and the fields are defined by Volkswagen. The breakdown of these values can be found in the service information for the vehicle. To demonstrate locating this information in AllData I have chosen a 2000 Jetta. The path that takes me to the information is as follows: Powertrain Management > Computers and Control Systems > System Diagnosis (Testing and Inspection) > Scan Tool Testing and Procedures > Reading Measuring Value Blocks (Function 08). Interpretation of this information can take a little practice. Another resource that is a bit easier to decipher is located on line at: http://www.ross-tech.com/vag-com/m_blocks/ . I will use this resource for the remainder of this article.

In the next example I have ...

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