C4 HDi100 BHY (=DV6FD): upstream NOx sensor location?

[marsalek]

Dear colleagues,

gettig error U029E87 meaning "upstream NOx sensor lost communication". Under the car located one, but at the end of the SCR catalysator. When I disconnect that one for a while, getting additional error U029D87 "downstream NOx sensor lost communication". This means, I found the downstream one.

But, WHERE IS the upstream NOx sensor located? At the front of the engine, going off the turbcharger, there is an oxygen sensor at the top of the oxycat/FAP. Then, going down the pipe I see the diesel(?) injector, then the bent pipe above the front axle and then the pipe goes to the SCR cat. But the upstream NOx must be between those two cats? Where is it, please???

Thanks a lot
Karel

[marsalek]

Well, I am getting the impression,
1. there is ONLY ONE NOx sensor on that car.
2. The U029E87 meaning "upstream NOx sensor lost communication" or likely "communication error with the DeNOx system" could also mean no communication with the AdBlue tank ECU, where the e.g. pump is located

So tomorrow I will remove the AdBlue tank from the carm check the wiring to the tank and if necessary open the tank's ECU compartment.