BMW F15 Diesel Fuel System Selective Catalyst reduction (SCR) Pump Testing

BMW diesel models are equipped with a dual-tank selective catalyst reduction (SCR) system. The SCR system is designed to reduce harmful emissions from diesel engines. The system works by injecting a urea-based solution called AdBlue (diesel emission fluid (DEF)) into the exhaust system, which then reacts with the exhaust gases to convert harmful nitrogen oxides (NOx) into harmless nitrogen and water vapor.
Adblue is injected before the SCR catalyst through a metering valve. NOx reduction is monitor using Pre- and Post-catalyst NOx sensors and using the feedback from the sensors the DME calculates the volume of Adblue injection. The ratio of NOX to NO is monitored to determine reduction effectiveness. When Adblue injection occurs, line pressure can reach 6 Bar. When the engine is turned OFF, the lines are partially drained to prevent damage from freezing.
In this video we will focus on the 4th generation dual-tank system found in F15 X5 models with a 3.0l engine and common problems you may see in your shop. First, let’s review a few tests for the metering valve and the AdBlue. Then we’ll see how to test the common issue of a faulty SCR transfer pump.
•AdBlue Mixer: Check that the mounting tabs on the mixer are facing the rear of the vehicle. If the tabs are facing toward the front of the vehicle, the dosed AdBlue will not be distributed properly. [Photo bmw.scr.001]
•AdBlue Quality: Check the quality of the AdBlue using a refractometer. Evaluating the AdBlue mixture: Normal Range: 31,8% - 33.3%.
Values lower than 31.8 % will cause an improper AdBlue mixture function and possible freezing.
Values higher than 33.3% indicate too low water mixture in the AdBlue. This can occur from a leaking SCR Tank causing water evaporation.
•Metering valve: Look for Adblue deposits around the nozzle. No deposits should be present at the nozzles. Deposits at sides of nozzle have no effect on function unless the deposits overlap the nozzles. The deposits have a consistency like toothpaste and can be easily cleaned, Recheck spray pattern after cleaning.
Check injection pattern using a paper towel. At a distance of 7.8 - 8.7”” (20 - 40cm) before the uncovered metering module, look for three evenly distributed circles. At a distance of 6” (15cm), the metering valve injection pattern should form a circle.
Before digging too deep into any issue, be sure to check for technical service bulletins (TSBs) or software updates. If you have any of the following fault codes, check that the vehicle you are working on has the latest DME software and the AdBlue quality is OK.
•26F500 - SCR system, efficiency: Efficiency too low
•26F600 - SCR system, efficiency: Efficiency too low
•2C4E00 - SCR system: System error and poor urea/water mixture quality detected
•26FD00 - Reducing agent metering, long-term adaptation: Adaptation value too high
•29FB00 - SCR system, warning and deactivation scenario: Warning level 1
•29FC00 - SCR system, warning and deactivation scenario: Warning level 2
•2B6200 - NOx sensor before DeNOx catalytic converter, plausibility: Sensor self-diagnosis of sensitivity
•2B6300 - NOx sensor After DeNOx catalytic converter, plausibility: Sensor self-diagnosis of sensitivity
SCR Transfer pump testing
2015 BMW X5 F15 models use a dual-tank Urea system, one active tank to feed the catalyst and one passive tank to store additional fluid. Having dual-tanks enables the vehicle to travel longer distances between AdBlue fill ups.
There is a transfer pump between the tanks. The transfer pump moves fluid from the passive tank to the active tank to maintain fluid level. This transfer pump can fail, causing incorrect Urea levels.
iSCAN BMW diagnostic software has a built-in service function to perform a transfer test. This test can be used to confirm the pump is functioning.
In the service function menu, locate SCR system, then select Activate Recirculation Pump to begin function. The transfer pump is activated until the active tank is full. The transfer pump is activated until the active tank level reaches 98%.
If the AdBlue level does not change, the pump may be faulty. You can quickly test the pump by listening for it during activation as well as testing it electrically. Remove the splash shields at the left side middle of vehicle, near the driveshaft.
Bring OE level diagnostic service to your Mercedes-Benz customers, with iSCAN.
iSCAN sf: www.iscantech....
iSCAN: www.iscantech....
Need help with a diagnostic issue. contact iSCAN Support On Demand SOD: www.iscantech....