SCR system giving P20E8 code

Amin Mechanic Ontario Posted   Latest  
Updated
Emissions
2011 BMW 335d 3.0L (M57T2D30) 6-spd (A6HP26Z)

I have a BMW 335d and the DEF system is causing some issues. The active tank was replaced due to DTC related to faulty level sensor and temp sensor. After 3 months of no issues , then got a DTC P20E8 low resultant pressure. After investigation I determined that the Def pump was faulty. Replaced def pump and DTC did not go away. Did I need to prime the def pump? Any suggestions on what next steps to take?

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Nicholes Technician
Pennsylvania
Nicholes Default
 

I’m not really sure how bmw systems work but I would assume it’s like cummins that I work on. Normally you can like have to run a quantity test or a leak test so It can see it building pressure.

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Mihail Technician
Maryland
Mihail Default
 

I have not done a bmw def pump, but on Mercedes diesels the scanner has a test for the pressure the pump can build up and the volume it can deliver. For the volume it just makes you disconnect the doser and collect the fluid in a container for a few seconds and then measure it. I am pretty sure you should be able to do those tests and get some idea what is wrong. Good luck.

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Eric Technical Support Specialist
California
Eric Default
   

Amin, No, you do not need to prime the pump. The fault is set if the Delivery module fails to reach a min. of 3.5 bar in 10.5 sec after 3 attempts (normally it hits 5 bar with no problem). Can you hear the pump run? Do you have a scan tool that will show you DEF pressure; possibly as part of a Metering Module dosing amount test? Do you have any other DDE faults stored? Is there DEF in the…

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Helpful
Michael Owner/Technician
New Jersey
Michael Default
 

I don't know if Canada is the same but I had a customer with the same vehicle and BMW warrantied everything to 150K

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Eric Technical Support Specialist
California
Eric Default
 

Michael, Canada has a history of not honoring the extended warranty bulletins. Only the Active tank and NOx sensors would be effected by that. Regards, Eric …

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Amin Mechanic
Ontario
Amin Update
 

After full diagnosis of the DEF system including metering valve,metering line, delivery pump, both active and passive tanks and transfer pump. The final result was that the BMW dealer who put in the active tank had reversed the tubes going into the transfer pump effectively creating a situation where the delivery pump could not create enough pressure in the metering line. the transfer pump was…

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