Special thanks to Tim from Adrenaline Vans for the following information. 'This has been our solution when replacing the factory bumper and eliminating the fog lamps on Sprinters. This has worked for us 100% of the time so far on both the NVC3 and VS30 platforms. That being said, I am not an electrical engineer, all I can say is this solution has worked flawlessly for us to eliminate the fog lamp warning that will come up when the original bulb is removed.' -Tim
Make sure the vehicle is turned off and the battery is disconnected
We use this product: 50w 5ohm resistor available on Amazon
Remove factory bumper and leave fog lamps hanging from wiring harness
Cut wiring harness just behind the factory plug that goes into the back of the fog lamp
Remove the protective wire tape from the two leads (purple and brown generally) and bare the ends of the wire
Solder the resistor listed above between the two leads (you can also use terminal connectors should soldering equipment not be available).  There are also other versions of resistors available that include wire leads and crimp style wire taps.  This is also a viable option just be sure that the wattage and ohm rating of the resistor matches those listed above (50w 5ohm).  We prefer the solder option as it is a much more positive means of connection
Secure the resistor to the inside of the replacement bumper using 3M VHB double sided adhesive time.  Remember, this will get hot so keep the resistor away from other wiring. Using the double sided tape method it is easy to place the resistor in a location that doesn't contact other wires and is out of the weather
Once the rest of your sensors are installed switch on ignition such that the running light come on and ensure that no fog lamp warnings are present