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Hi, I know a few people in these forums have done this, and after plucking up the courage it was actually really easy to do. There's plenty of other posts detailing the VCDS codes that are apparent when the G395 sensor is faulty, so I won't repeat that here.

Tools Required :-
  • VCDS Cable
  • T-30 Torx screwdriver
  • 24mm crowfoot spanner (see below for a picture)
  • 3/8"extension bar
  • 3/8" ratchet
Parts required:-
  • G395 sensor (Part number 4H0 959 126 B) - See Note at the bottom
Here's how.

  1. At the very front of the engine bay, remove the 4 Torx30 screws from the plastic trim piece that covers the gap between the grill and the radiator,and goes the full width of the car. SEE PICTURE BELOW
  2. The plastic cover piece then just slides towards the back of the car and lifts off.
  3. You'll then see the G395 sensor mounted on the front of the radiator on the left hand side of the car (right hand side as you look at it). Might be on the opposite side on a RHD car, but I don't think it is. SEE PICTURE BELOW
  4. Unplug the connector from the top of it by squeezing the locking tab in and pulling upwards.
  5. You can then use the crowfoot spanner and extension to remove the sensor without having to remove any further bodywork on the car. It connects to a Schrader type valve (like a car tyre valve) so you will hear a very small hiss when you remove it, but you'll only lose a very tiny amount of gas, so it won't cause a problem.
  6. Screw the new sensor back on, and then tighten with the spanner and plug the connector back in.
  7. You'll then need to use your VCDS cable to reset the fault codes under the HVAC. I'm not positive that this step is essential to it working again, but I did it anyway as it's a good way to check that the fault code doesn't come back,and that you have solved the problem.
  8. When refitting the plastic trim piece the front edge of it slots into 4 slots in the grill, and then it locates itself over 3 little grey plastic nibs that stick up through holes in the front of the plastic trim piece. Obviously then just screw the 4 screws back in.
Note: I'm sure the official process is to remove the front grill and get at it that way, or maybe using a long 24mm socket would do the job (a standard 24mm socket is no good as the connector at the top is too big). I used a crowfoot spanner, 3/8" 3" long extension bar and ratchet, and it was incredibly easy. SEE PICTURE BELOW

Note: The original part on my car was a 4H0959126. I understood that this had been superseded by an updated part 4H0959126A which I bought as an OEM part for just under £30 from a motor factor on ebay. This did not work. I then went to my local audi garage and the parts guy said that there was an even newer version out 4H0959126B. I bought this genuine part (for £65.27 inc VAT) and it worked perfectly.
which vendor did you buy it from so i dont buy that one!
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