Fixed my 4BCC CEL
 

Hey guys, new owner/member here. Picked up a 2011 X5D and it had a CEL pop up for 4BCC on the drive home. It was a deal and we knew it was going to have issues. Dig into the forums here (and bimmerpost) to research best practices for repair/upgrades to issues.

Found the price of the passive def tank ridiculous so I went and built myself a, let’s just say highly functional, 4 wire patch harness out of a trailer wire extension because the connector is basically water tight and the wire colors basically match the existing level sensor harness. 10k ohm resistor soldered in between each wire and the signal wire. With a second harness cut in two and wired in I can replace or update the harness if needed.

So I crawled under the car, pulled the passive tank out and went wait. Where is the 4 wire harness? Time out, back to forum, realize I built a harness for the active tank. Doh! Go back out, measure resistance on each level sensor and find the top sensor has an open circuit.

Started looking at where the best place to wire a resistor would be, and I looked at the end of the harness.

Well, I think a resistor will fit in that corner and I can just stick some leads into the connectors.

Well what do you know, it works. Plugged everything back in and cleared the code. Two days later and still clear. Going to fill the tank and get our smog test done.

Happy to help with any questions and will do a proper intro post once I’m on a computer and not my phone. Sorry the photos wouldn't load directly from google photos, so I had to shrink them and attach manually.

Hello, if you don’t mind, can you explain a bit in detail what you did? I am getting the 4bcc error code too. There are two sensors I’m thinking on the passive tank. One for high level and one for low level def.. As a I have DEF in the tank what should the resistance reading be on the wiring? Is it a 10k ohms resistance when the tank is empty or full or doesn’t matter on fill level?

On the 335d i was able to buy the active/passive tank “basket type” sensors from VW rather than purchasing the entire DEF tank from bmw. That was a direct diy install.

Thanks

My issue was with the upper sensor. Take a multimeter and measure the resistance between both terminals of the sensor. If it's open (infinite resistance) then just slap the 10k ohm resistor in the connector and reconnect. Same should work for the lower sensor too.

adriang, would you mind sharing the VW part numbers for the sensors mentioned above. Also, if you have any pictures I would really appreciate you posing it.


Thank you!

ttt

watching this one closely

in 2017 it was around $330CAD+tax from the VW dealership. The VW part # is 7L6 198 970 A

I have a step by step instructional with pictures on the internet if you search adriang active tank sensor replacement

Can you please specify what 10k resistor your used? 1 watt?1%? Also, was this for the temp sensor or level sensor? Thanks

I just used a 10k ohm 3 watt I believe. A 1 watt would be fine as it is just a resistor to complete the circuit when the level sensor reads low. There is no heater in the reserve tank.

Excellent, thanks.

looking at the picture, looks like a sub one watt


the dimensions will tell you...1/4 is 6.5mm long by 2.5mm...1/2 is 8.5mm L x 3.2 dia