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Passive Tank Replacement - Need confirmation of VW Part

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Hi All,

I've been driving with the 4976 and 4BCC code for almost a year now (I got the CEL 1 month after 10 years had passed and I was at 80K but BMW NA said NO to goodwill after multiple tries). I got the codes via Carly before taking it to the Indy yesterday.

4976 - NoX Sensor
4BCC - Passive Tank

Anyway - I need to tackle the job now so went to the Indy who ran diagnostics and confirmed the above codes (see attachment) and the recommendation is to change the Passive Tank and NoX sensor = Total Quote $3400.00 which is a No Go ($2100 just for the passive tank, rest NoX and Labor)

After reading multiple threads etc - I'd go with the cheap VW part and that's where I need help to confirm the part number since there seem to be different revisions as well so I want to make sure I get the right one.

So far, I see that there are two part numbers: 7L6-198-970-A and 7L6-198-970

From one of the threads someone shared the below link but part numbers are 7L6-198-970-B and 7L6-198-970
https://www.ecstuning.com/b-genuine-volkswagen-audi-parts/rep-kit/7l6198970b/ but the ECS fitment says it doesn't work for E70 35d.

I also saw some threads mentioning at "Bosch" part but I can't find the part number. Can y'all confirm the correct part. Also, I'm in Houston so if there's an Indy you know who has done this before, do let me know.

Attachments

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Thx for the reply @Attacking Mid . Did you mean "active" instead of "passive" in your comment. "Most diesel drivers have adopted the practice of filling their passive tanks with 2.5 gal"

The code that Carly and Indy pulled are: 4BCC (Passive Tank Level Sensor) and 4976 (NoX) so that's all I have.

I actually filled the Active Tank today and it barely took 500ml which means it was pretty full already. So there's no transfer from Passive to Active anyway.

Should I just drain out the passive tank and keep it empty? I'm going to take the car on a long drive for 250 miles and see if active tank is even being used - hopefully it's not the metering valve but again Indy said - he only pulled the above 2 codes.

I was thinking the following potential solutions just not sure in what order:

Xemodex Passive Tank Repair (Just like you I'm not sure if it's the passive Tank at all)
Change upstream Nox Sensor
Clean EGR Valve
(Clean DEF Injector + Change Metering Valve) - That's what someone did in of the threads.

2nd Edit: Are you sure the passive tank level sensor is the culprit of your CE light? Frankly, I couldn't care less about that level sensor. Most diesel drivers have adopted the practice of filling their passive tanks with 2.5 gal. of DEF once they get the 1K mile countdown warning (which is triggered by the level in the active tank). I'm actually only putting in a gallon or so, as my 8-10K annual mileage means 2.5 gal. of DEF would sit out in the elements (sun) longer than I prefer.

AM.
Thx @Attacking Mid

Need to find out if I can change the NOX sensor myself. There are 2 and each costs 500+.

Forum members- Has anyone here changed the NOX sensor DIY? How easy difficult it is?
Thx for the reply Edycol. I need to plan the exact approach before I go to the dealership. The car is 11 yrs old with 87K and worth 9K. So, I want to have a plan and be smart about the sequence of "throwing parts at my expense". The CEL has been ON for a year :)

I had Indy to the diagnostics and they said replace passive tank and O2 sensor and that didn't make sense based on what I saw in Carly so will take it to the BMW dealership next week.

Should I have the DEF injector cleaned and Metering Valve changed + clear EGR valve even before going to BMW?

And then work on
1.) Nox sensors
2.) SCR Cat
3.) Passive Tank



NOx sensors have to be calibrated. Also, be ready for some more bad news. NOx sensors are like O2 sensors, they have to agree. Best approach is both sensors to be replaced. But, wait, there is more: your SCR cat might be culprit or DEF injector. If they don’t do their job properly, it might show as bad NOx sensor.

Passive tank level sensor? Just put resistor and make sure you always have DEF.


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Is this the thread you're talking about?

I'll take it to BMW sometime soon but really thinking is 4-5K (SCR Cat/NOX sensors) worth spending on a 9K car :)

Well, if you can clean it, it would not hurt I guess. My SCR cat died right around that mileage. BMW thought sensors were an issue, but it turned out to be SCR cat.


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