prime it just to make sure I will not burn the new motor?

I believe that all of the DEF/SCR pumps are diaphragm positive displacement pumps. The schematic symbols are the same.

Transfer Unit
The transfer unit pumps the urea-water solution from the passive reservoir to the active reservoir. There is a screen filter in the inlet port of the pump.
This pump is designed as a diaphragm pump. It operates in a similar way to a piston pump but the pump element is separated from the medium by a diaphragm. This means there are no problems regarding corrosion.

[Delivery]
The pump is actuated by a pulse-width modulated signal (PWM signal) from the DDE. The PWM signal provides a speed specifica- tion for the purpose of establishing the system pressure. The value for the speed specification is calculated by the DDE based on the signal from the pressure sensor.
When the system starts up, the pump is actuated with a defined PWM signal and the line to the metering module is filled. This is followed by pressure build-up. Only then does pressure control take place.

 

Active tank is under 10yr/120K warranty.

 

for now I need to make sure the problem is the active tank before taking it to the dealership. I don't like to experience the last time I had an active tank problem and the dealership was trying to replace the catalytic converter. But later on just replaced the active tank and car was fixed. Since the supply module pump is not a part of the active tank warranty I have to check it first.

Thanks for letting me know about the updated warranty on the active tank :thumbup:

 

UPDATE:

So i just got the supply module this afternoon. Installed it and run test. After running the engine just enough to raise the temperature I checked the status of scr system and showed the pressure 5000 hPa. Before I had 0 hPa. I will be testing the car tomorrow until all the readiness monitors will show "concluded" since I cleared the fault and hopefully no more check engine light.

 

I have the same code on my 10' 335d, code 4804.
Replacing the supply module fixed your problem? Is the part hard to get to?

Thanks,

 

I have this same problem on my 2010 X5d at almost 90k. CEL light is on. Carly says "Reducing agent no reducing agent pressure build-up possible Code: 004804" X5 runs great, so in no hurry to take to a shop. Will watch this thread.

 

if your inspection is not due anytime soon you have all the time to diagnose and fix the problem.:thumbup:

 

Any links on how to check or replace the module?

 

I realize this is an old thread, but wanted to add my experience with code 4804, as well as answer the question posed by salman13.

So my son's 2010 35d came up with this code (4804). We replaced the supply module part # 16197244137 from fcpeuro. As noted by Thirdy in post #9 above, the supply module sits on top of the active tank. Once the active tank is removed, it is fairly trivial to swap out the supply module. Three hex bolts, a few electrical connectors, 2 fluid line connections, and 2 new o-rings. The best description of how to remove the active tank I found is this Youtube video.

Overall quite straightforward, perhaps the 2 most difficult parts are 1) when removing the fender liner keeping the various plastic rivets, 8 mm bolts, and a few philips screws straight to remember what goes where when putting it back, and 2) removing the electrical connections to the active tank require access via popping the front fender trim piece (discussed in the Youtube video above).

It took us about 2 1/2 hours, and the CEL went out all on it's own within the first hour of driving.

Hope the above helps someone out in the future.

Stephen