I recently took my headlights off to replace a faulty D1S bulb, so while I was at it I used the opportunity to update the City Lights, too. Unlike my LED DRL DIY, these bulbs actually don’t need resistors as the can-bus module is built-in, so the installation was plug-n-play! Another great thing about this mod is that you don’t have to remove the bumper/headlights to install, as you can access the bulbs through the side port/opening of the headlight, making them very easy to install. This DIY should be applicable to all B7 Audi A4, S4 or RS4 regardless of whether it is equipped with xenon or halogen headlights – my 2006 Audi S4 with bi-xenon headlights is pictured in this post.
Update: after using these for several months, these may trigger a “parking light” error when you first turn your car on, but that will go away as soon as you turn your main beams on, or as the car warms up. It doesn’t happen every time, just some times. If you want to add a resistor to fix this so they NEVER show an error, I have amended this post with details on how to do that!
The exact bulb I’m using is a CAN-BUS enabled 194 wedge bulb made by JDM ASTAR that was purchased off Amazon. So far I’ve used them for about a week without an errors, flickering or other issues, so the error-canceling technology (CAN-BUS) built-in to these bulbs seem to work well with the 2006-2008 B7 Audi A4/S4/RS4. If you try a different bulb, be sure to buy one that is smaller, as the hole/opening in the headlight housing will not accommodate anything much wider than stock, and you’ll want to make sure it has a built in error-canceler/CAN-BUS system otherwise you’ll need resistors.
As you can see, the color of the bulbs is white with a hint of blue, which matches my other LEDs quite well. Despite this being a pretty small bulb, it emits nice light and looks very good. The City Lights, unlike the DRL bulbs, come on when the parking lights or headlights are engaged, but are not typically on during daytime use – they’re basically the opposite of a daytime running light and usually only come on in night-time use. If you have bluer headlight bulbs such as 5000K+ D1S bulbs, then these LED City Lights will match those quite nicely, as opposed to the stock 194 halogen bulbs that look yellow in comparison.
This is a very easy mod so not much else to write here – it’s a great value at under $15 with shipping and tax, and seems to work as well as other bulbs I’ve seen on sites like ECS Tuning for almost tripe the price! If you have any questions or issues, post in the comments.
Adding Resistors (Optional)
If you’d like to add resistors, you can pick up some fairly low watt and ohm resistors for this. While a number of different resistors will work, Audi’s CAN-BUS system only looks at Ohms, so pick up anything greater than 6hms with the lowest wattage you can find and you’ll be good. I went with these resistors, then ran the wires outside of the headlight and mounted to the inner fender:
If you wanted resistors that are “plug and play” in terms of install, then pick up these instead – they’ll run a little hotter, but as long as you mount to metal such as the inner fender it shouldn’t be an issue: