just posting some text from my tech article. Hopefully, this info will be of use to those who are interested in doing the Nav+ updgrade. -ted (feel free to add any comments in a reply post. Thanks!) The TMC/CAN gateway is a device used in Europe to capture Traffic Message Channel (TMC) information via the radio station and sent to the navigation units to enable you to navigate around upcoming traffic delays or accidents. TMC is a service that you pay for in Europe. In Europe, it can be transmitted within standard public audio broadcasts - in the UK it is carried by ClassicFM, or obtained via cellphone calls.Â Unfortunately TMC was not adopted in North America. Therefore the TMC portion of the device is not used. What is CAN? CAN is the databus that all/most/some of the electronic systems use to communicate. Essentially correct - CAN (Controller Area Network) bus was developed by Bosch, the German electronics company. - Definition courtesy of Peter Bell (email@example.com ) The CAN portion of the device is used to translate the navigation, radio and CD information from the Nav+ to the instrument cluster. FYI â€“ The Nav+ is developed by Blaupunkt for Audi as an OEM component. The TMC/CAN gateway translates those CAN signals from Blaupunkt to Audiâ€™s protocol. In the D3 A8 and the C6 A6, CAN will be used more widely to integrate all components together into one network. The TMC/CAN gateway is optional and not required to use a Nav+. The TMC/CAN device can be purchased new from Vagparts.com for $400 or used (via ebay.de) for $100-$250. Prior to purchasing all of my Nav+ parts, I determined that having the navigation information on the DIS was mandatory for me. In my opinion, it is too much of a safety hazard to be constantly looking at a map screen while driving. As an A6 owner, this was the purchase criteria that I used: 1) Navigation information on DIS: In addition to the cool map display, you get directional arrows in your DIS for right turn, left turn, etc. The best part is that it gives you a total driving distance to your destination, estimated time of arrival (ETA) and the mileage before your next turn. The ETA is also being recalculated depending on the speed of travel. This allows you to keep your eyes on the road. I tend to look down at the map display when I need a point of reference in my travels. Also, I can toggle the DIS information (using the reset button on the right side stalk) between the navigation/map display and the outside temperature/trip computer display. Very cool! 2) Use of Steering wheel/Radio/CD controls: Also, in an A6, the TMC/CAN gateway will allow you to retain your steering wheel radio/CD controls when you upgrade to the Nav+. The steering wheel (with radio/CD controls) is just one particular â€œnodeâ€ that resides on the CAN-bus network. In 2002, A6â€™s began to use the CAN-bus network to connect all kinds of electronic â€œnodesâ€ into this system. 3) Street/Highway information: While in map mode in the Nav+, the DIS provides you with a compass (N, S, E, W) and a label for the street or highway name. I really like knowing what street/highway I am driving down; this is a cool feature that the US-based navigation option doesnâ€™t offer. Source for TMC/CAN units: A) Ebay Germany ( www.ebay.de ): I bought mine from Ebay.de and it cost me $220 (shipped). There are several individuals from Europe selling these units. Even a used unit will function the same as one purchased new. B) www.vagparts.com (search under products and SAT Nav Plusâ€¦.it's in there) (FYI - If you decide to order this from Vagparts, you might as well spend the $18 on a hardcopy of the Nav+ usermanual and any other connectors/wires/pins that you need. Expect to wait at least 5-10 business days for these parts to arrive.) C) http://www.euro-audi-parts.com ( firstname.lastname@example.org ) I have not dealt with these folks for Audi Nav+ components. D) www.nav-plus.com I have not dealt with these folks, but they sell all kinds of Nav+ â€œadd-onâ€ components for enhancing the audio/visual experience of your Nav+. Also, you can search under the vwnavi.com forum/classifieds for Audi TMC/CAN units. I see them for sale over there from time to time. It is not certain whether the VW TMC units (start with 3BO-XXX-XXX) will work in an Audi Nav+. However, it is my theory that the CAN function for North American users should translate the same via a TMC/CAN part# 4B1-XXX-XXX etc. http://www.vwnavi.com/vwnavi/forums/index.php Part numbers for the TMC/CAN gateway: There are three different versions that will work with your A6/S6/RS6/allroad (per Vagparts.com). Because those of us in the United States are only using the TMC/CAN for its CAN translation capabilities, it has been proven that any version below will work. Audi Part# TMC/CAN Fitment 4B1 919 894 CAN for all A6/S6/RS6/allroad; TMC for MY2000 â€“ 01 4B1 919 894A CAN for all A6/S6/RS6/allroad; TMC for MY2001 for vehicles in Spanish / French market 4B1 919 894B CAN for all A6/S6/RS6/allroad; TMC for MY2001 â€“ 04 Please note: It has been proven that any 4B1 version will work in a US-based Nav+ installation. The 4B1 version has the CAN translation firmware in it. Per Dan Gold, there is a TMC Tuner only version (part# starts with 4B0) and a TMC/CAN gateway version (part# starts with 4B1). You will notice on some of the 4B0's there is a large blue connector as well. The 4BO version is only for TMC functionality. DO NOT PURCHASE the 4B0-XXX-XXX version as it will NOT translate the navigation/CD/radio information to your DIS; the 4B0 model is just a TMC tuner. Other TMC/CAN parts needed: Audi Part# Function 4A0-972-883 12 pin connector 000-979-003 Wires/pins (this will come with two pins attached by one wire â€“ at a minimum, you only need three or six pins) Please note: These parts can be sourced directly from your local Audi Parts department. They are considered a special order item and can take up to a week to arrive. Please note: If you end up ordering a TMC/CAN gateway from www.vagparts.com, it will be cheaper for you to include these pins/wires and connectors as part of your order. Also, it has been proven that CAN gateways can work across the A4/A6/A8 model range (a C5 A6 unit has been tested and worked in a B5 A4/S4). The reason that the VAG part numbers are different is because of the model-specific mounting bracket. Per Jon Lofquist: the 8E0 unit TMC will work with any of the nav+ units for CAN Gateway function.Â I have tested my 8E0 919 895B TMC with 4B0, 4D0, 8D0, and 8D0 navis.