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Discussion Starter #1 (Edited)
Just wanted to post a DIY fix for the dreaded adblue tank temp sensor. Before posting I wanted to insure it would work. I've been running it for about six months now with no issues. This is only for the temp sensor failure and not the heaters or pump. Some may get other codes if the temp sensor fails during colder months, so you need to insure that it's just the temp sensor. Easy way to do this is clear all codes and when the CEL comes on check codes to see if it's just P205B.

You will need a 10k thermistor which can be purchased off eBay for $1.99-$10.00 depending on quality. Make sure it is H20 proof. You can find these labeled as aquarium tank temp sensors, but must be a 10k ohm.

First you need to remove the tank. Find the connector attached to the fill neck. This is where you are going to connect the new sensor. The small black and white wires on the bottom are the temp sensors. These are the two wires to connect the new sensor too. Make sure you cut them on the sensor side black and white and not the other side of the connector. This will allow plug and play if you ever have to replace the whole unit. Make sure you cover/seal the bare wires from the old sensor as to reduce creep down the wires into the tank.
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I drilled a hole into the fill cap as this was a trial fix and the cap is a lot cheaper to replace than the whole tank. Run the new sensor through the hole and make sure you have enough wire to reach the bottom of the tank. Make sure that if you use this method that you seal the hole with silicone to prevent leakage through splashing. You can use your own method for getting the sensor in the tank, but remember some day the pump or heater may go out and you will have to replace the whole unit, so then you could replace the fill cap and it'll be like new.

I did have to replace the sensor once because when I first did this I used a used one from a fermentation temp controller I had. Below are some photos of the fix.
 

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Thanks for posting this. Maybe I missed it, but where is the actual OEM sensor located? Is it part of the pump assembly?
 

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Discussion Starter #4
Thanks for posting this. Maybe I missed it, but where is the actual OEM sensor located? Is it part of the pump assembly?
It's part of the entire pump assembly. If sensor fails you have to change entire heater/pump assembly unless you do above method. I've been running this temp fix for about 1.5 years now with no issues.
 

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When you use this method, I see that you are to connect the new sensor to the black and white wires, but it also looks as if the other two wires to the plug are cut as well, is that the case or does it just look that way in the picture?
 

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Just wanted to post a DIY fix for the dreaded adblue tank temp sensor. Before posting I wanted to insure it would work. I've been running it for about six months now with no issues. This is only for the temp sensor failure and not the heaters or pump. Some may get other codes if the temp sensor fails during colder months, so you need to insure that it's just the temp sensor. Easy way to do this is clear all codes and when the CEL comes on check codes to see if it's just P205B.

You will need a 10k thermistor which can be purchased off eBay for $1.99-$10.00 depending on quality. Make sure it is H20 proof. You can find these labeled as aquarium tank temp sensors, but must be a 10k ohm.

First you need to remove the tank. Find the connector attached to the fill neck. This is where you are going to connect the new sensor. The small black and white wires on the bottom are the temp sensors. These are the two wires to connect the new sensor too. Make sure you cut them on the sensor side black and white and not the other side of the connector. This will allow plug and play if you ever have to replace the whole unit. Make sure you cover/seal the bare wires from the old sensor as to reduce creep down the wires into the tank.
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I drilled a hole into the fill cap as this was a trial fix and the cap is a lot cheaper to replace than the whole tank. Run the new sensor through the hole and make sure you have enough wire to reach the bottom of the tank. Make sure that if you use this method that you seal the hole with silicone to prevent leakage through splashing. You can use your own method for getting the sensor in the tank, but remember some day the pump or heater may go out and you will have to replace the whole unit, so then you could replace the fill cap and it'll be like new.

I did have to replace the sensor once because when I first did this I used a used one from a fermentation temp controller I had. Below are some photos of the fix.
I've just joined up to say thanks for this post. I've just finished putting a temperature sensor in and have got rid of the little orange light! I ran my sensor through a hole in rhe filler neck that I made with a soldering iron and sealed with a hot glue gun. Time will tell how it lasts but at least I won't have to clear error codes every trip.
 

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nick_

First posts normally go in introductions else you could get a free fix and we never see you again!!!

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VAG Error Code: 9688

EOBD II Error Code: P205B

Fault Location:
Reductant Temperature Sensor - Circuit Range/Performance Problem/Implausible Signal

Possible Cause:
Malfunction Indicator Lamp (MIL)(K83) active.

Wiring/Connector(s).
Reductant Temperature Sensor.

Possible Solutions:
Check/Replace all faulty Wiring/Connector(s).
Read Measuring Value Blocks (MVB).
P205B temp sensor DIY fix.

As taken from my new Free EOBD II Error Codes software
 
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