I recently purchased a 2003 allroad that was throwing codes for the egt sensors. I searched around a bit and found that some people have been able to successfully repair their egt sensors by resoldering the 5 solder points inside of the sensor. While this seems to have worked well for one of my sensors, it did not work for the other. I still received the following code, immediately after clearing it:
17861 - Exhaust Gas Temp Sensor 1 (G235)
P1453 - 35-10 - Open or Short to Plus - Intermittent
So, I figured I was going to have to fork over the $250 to buy a new EGT sensor, which by reports, would probably have a similar fate a couple years down the road. Instead, I did a little searching and found a thread where a guy replaced the circuit board (pcb) of the egt. The intent was so he could have a real time reading of his egts in cabin. I'm not going for real time readouts here, but just want to fix my egt sensor, and slap my car out of limp mode. So, with a little more searching, I found a guy in Poland who makes a replacement boards for these egt sensors. I was able to contact him through email, sent a paypal for $45, and received the new egt pcb in the mail a week later. Great service, fast shipping, and a cheap price for what I hope is a permanent solution.
Time for a mini DIY:
First, it's best to remove the sensor from the car completely. For the driver's side, it might be better to get do this all with the probe attached to the exhaust, since it's a real bugger to remove.
Open the box of EGT sensor. There's a bunch of slimy silicone that was used to protect the board. Remove all of this junk. I used a toothbrush to remove what I could.
Once you've removed as much crap as you can, you'll need to remove the circuit board from the box completely. You can use a solder gun to melt the solder and remove each leg one by one.
After the pcb has been removed, get the rest of the box as clean as possible. I used some engine cleaner and let it sit for a few minutes to break down the rest of the silicone. I then blasted the box with compressed air to remove most of the remaining junk, followed by a light wash down with brake parts cleaner. I then cleaned up the leads as best as I could to remove any extra solder. I mostly needed to do this because I attempted to fix the unit by resoldering the legs first.
Here's what the box looked like before soldering the new board in:
Next, solder in the new board. This is pretty easy, just make the wires find there way home in the middle of the leads.
Use something to secure the board to the box, double sided tape, dab of rtv, whatever. I used rtv silicone to seal the box shut again, and held it together for an hour or so with a clamp, and reinstalled. Note: I did not encase the pcb with silicone like it was from the factory.
I started up the car, cleared the codes, and to my pleasure, the codes did not return!!!! SUCCESS!!! WOOHOO!! I also took some logs with vagcom, and where the ECU was only ever requesting 6-7lbs of boost before with the egt codes, it now is requesting 10-12lbs and my car has lost the sluggishness it most surely gained when the egts failed.
And finally, here's all the information you need to know about how to order the new circuit boards.
I was able to contact him via these emails:
Forget about buying stupid oem replacement egts for > $250 a pop that will probably fail again in the near future. Spend $45 to get a new board or $84 for both boards shipped to your door. I still am amazed by how fast they got it shipped over here.
Credit must be given to this audizine thread