NOx sensors - another beast to tame?

Ok, they have been around since the mid 2000s at least but with the increase in Gas Direct Injection they are about to become a lot more common and I've just hit my first one on VW Gold FSI 2.0.

This one has 8 wires - yes 8 - from the post cat sensor, which not an oxygen sensor and not an AFR/wideband (though similar) but is a NOx (nitrous oxide sensor).
The sensor is coupled with a Control Module that receives the colorful spaghetti of 8 wires, and then spits out another 4 wires on the other side of the module, which presumably make their way to the PCM.

Hard enough so far to even determine which is the signal, let alone whether a NOx output signal to the PCM is High V for Rich or Low V for Rich, or what the expected waveform would look like.

Got a P1033, which is a low signal code ... Seems this is a common fault but can sometimes be wiring rather than sensor/module related.
Any help all ... starting from first principles ... would be very much appreciated. Not much online, I can tell that much.

In my experience with working on semi trucks, which use 2 NOx sensor modules, there is not much info out there on testing them. None of the manufacturing flow charts focus on the 8 wires at all. The 4 wire plug in is where all of the testing gets done. 2 wires are power and ground. The other 2 are for CAN communication.

If you're getting a low signal or out of range drifted high error odds are its a faulty sensor module.

Basic checks are power and ground, and then ohm out the CAN line, and if it's in spec change the sensor.

There are a couple of ADP videos that go into basic theory and operation of a NOX sensor but again it's usually little help.

Check your fuel trims and take care of upstream malfunctions before replacing the sensor.

Chriscoy wrote: In my experience with working on semi trucks, which use 2 NOx sensor modules, there is not much info out there on testing them. None of the manufacturing flow charts focus on the 8 wires at all. The 4 wire plug in is where all of the testing gets done. 2 wires are power and ground. The other 2 are for CAN communication.

My experience is the same. On the few times I've had to go after Ford NOx sensors in light duty trucks, the service info is pretty useless. NOT confidence inspiring, especially given how expensive the sensors are.

No one I follow has any real info on sensor testing