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2007 3.2 VR6 Quattro Roadster
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For the purpose of this discussion the term "OBDII Diagnostic Device" includes any diagnostic device that can be used to interrogate and report on the status of the electronic system of the Mk1, Mk2 or Mk3 TT by means of the OBD port. For the specific details on the differences between VCDS and OBDII, see the notes below.

As the market for OBDII scanners continues to grow in both popularity, options and price point, the Forum is collecting more information from our members on how to use these devices and their personal opinions on how well they work. Each manufacturer has their own functional capabilities and feature which generally include -

• Fault Scan
• Fault Clearing
• Service Reset
• Output Tests
• Adaptations & Basic Settings
• Code changes to enable or disable factory set functions

Three Reasons to Own One -

1.) The ability to find out for yourself what's going on with your car when you suspect there's a problem. Rather than guessing or depending on a service garage, you can quickly check it yourself, look up the fault codes and then decide if you want to tackle the repair yourself or take it into a service center. By knowing the fault codes ahead of time, you can have an educated discussion with the shop so you're less likely to get pulled over the table. For the DIY mechanic, think of an OBDII scanner like owning a torque wrench - you should just have one to do the job right.

2.) Access features not present in your TT when it left the factory and performing Adaptations and Basic Settings. For example swapping the OEM DRLs with LEDs is possible but you'll need re-code it in order to make this work. Other possibilities include Service Reset, Oil Service Reset, Reverse Camera installation, Needle Sweep, etc. Keep in mind not all years will have the same options or features.

Adaptations and Basic Setting are slightly different in how they are performed but are necessary when replacing sensors and some electronic components. An Adaptation involves entering a value, such as idle speed, where you have different choices. A Basic Settings is a single pre-determined routine where you have no choices to make such as when you replace a G85 Steering Angle Sender. If the Workshop Manual states a calibration is required after replacing a component, it will not be possible to clear the fault code until either an Adaptation or Basic Setting has been done. You can read more about Adaptations here.

3.) For anyone looking to buy a TT, it's always a good idea to ask the seller if they are willing to provide you with a fault scan as part of the pre-sale. If they refuse, you may want to walk away from the car or just take it for a test drive and run the test yourself. With any pre-sale, you should have a mechanic go over it so there are no surprises and include a fault scan as part of the inspection.

Just be aware not all scanners are the same. They can't all perform all Adaptations & Basic Setting, output tests or export data files and not are all coded specifically for VAG software. In a nut-shell, you get what you pay for with an OBDII scanner.

OBDII Reviews -

Below you will find a brief list of pros and cons for each OBDII scan tool along with a link to the Forum review and the product's home page. These are sorted by capability and price.

OBDII User Poll -

We also have a new poll going on just to get an idea of which of these is the most popular with Forum members. In all fairness, VCDS has been around for over 20-years, while the OBDeleven has only been on the market since 2015, but it's gaining popularity. To visit the poll, click here

1. Ross Tech VCDS (VAGCOM) -


FAQ - VCDS Open Box Review ... &t=1928927
Ross-Tech: Home
Ross Tech YouTube "How To" Channel

• PC based (Windows) usually used with a laptop
• Does not require internet access to work
• Has all Adaptations and Basic Setting functions
• Multiple Measurement Block viewing
• Live Graphing of multiple systems
• Data export
• Video Tutorials, Forum and Wiki pages
• Direct customer support
• Free software upgrades
Supports VAG software
• No additional costs

• Price
• Hex connector and cable
• Limited to 3-vehicles
• No programming short cuts; long code only

2. OBDeleven (FirstGen & NextGen)

Gadget Rectangle Font Musical instrument Electronic device

FAQ - OBDeleven Open Box Review ... &t=1926899

Note -
The FirstGen device (white) only works with Android. The NextGen device (black) works with Android and iOS however the iOS version does not offer the same functions as Android; e.g. charts and gauges are under development. Both the FirstGen and NextGen versions can support Audi, Volkswagen, Seat, Škoda, Lamborghini and Bentley, however the NextGen will support more car brands in the future. The functionality of both devices is the same.

• Android & iOS
• App-based for Smartphone/device
• Price
• Size (OBD dongle only)
• "One Touch" Apps for coding changes
Supports VAG software
• Free updates
• Unlimited vehicles
• Available as FirstGen (shown above) and NextGen

• Uses a credit system
• Requires "Pro" upgrade for improved access
• Pro version has an annual subscription fee (effective 16 June 2021)
• Does not have all Adaptations and Basic Setting functions
• Requires internet access to work (not stand alone)
• Limited technical support

3. XTool V401

FAQ - XTool V401 Code Reader ... &t=2012963
XTOOL Authorized Dealer

• Price
• Hand held, stand alone device (with cable)
• User manual included
• Unlimited vehicles
Supports VAG software

• Lack of customer support
• Last software update Rev (7.1) 2013
• Limited Adaptations & Basic Settings
• Can not show when a fault occurred
• No file output capability

4. Carista
Eye Product Liquid Rectangle Gadget

FAQ - Carista ... &t=2013801
Carista OBD2 App | Diagnose, customize and service your car

• Android & iOS
• Price
• Size (OBD dongle only)
• Unlimited vehicles

• Subscription based user fee
• Does not have all Adaptations and Basic Setting functions
• Requires internet access to work
Generic OBDII code reader not coded specifically for VAG software
• Limited technical support

VCDS & OBD Definitions

is an abbreviation for VAG-COM Diagnostic System, also known as VAG-COM which is a Microsoft Windows-based software package developed and produced by Ross-Tech. VAG is an abbreviation for Volkswagen Audi Group.

Unlike generic on-board diagnostics (OBD-II or EOBD), VCDS uses the more in-depth VAG-specific manufacturer protocol commands which allows the user to access all diagnostic capable vehicle systems - even in vehicles which are not covered by generic OBD-II/EOBD

On-board diagnostics (OBD) is an automotive term referring to a vehicle's self-diagnostic and reporting capability. OBD systems give the vehicle owner or repair technician access to the status of the various vehicle sub-systems.

Looking Up Fault Codes -

To understand what a fault code or Diagnostic Trouble Code (DTC) actually means, you can run a Google Search for "Ross Tech XXXXX" where XXXXX is the fault code. This will bring up a link to Ross Tech's wiki which will describe the fault code, possible causes and solutions. While Ross Tech has most of the VAG DTCs, they don't have all of them. If you can't find it there, you can look through this website - Engine Codes |

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