Condemning a BMW SCR catalyst?

Brandon Technician Medina, Minnesota Posted   Latest  
Question
Emissions
Driveability
2011 BMW X5 xDrive35d 3.0L (M57T2D30) 6-spd (GA6HP26Z)—5UXZW0C57BL660002
4D16 - Scr System Efficiency

We sold a 2011 X5 35d with the M57 to a customer that lives a few hours from us. It had a 4D16 - SCR system efficiency code found at her local Euro shop, they directed her to the dealership. She brought it back to us, that code is nowhere to be found, but I had an SCR active tank heater code instead. I verified the tank heater element was faulty and sent it to BMW to get replaced under the extended warranty, put some miles on it and confirmed the SCR monitor passed. I did another system test with ISTA before we delivered it back to the customer and it now has the 4D16 stored, but not current (nor historic). I dig into it, inspect the DEF metering valve and mixer per SI B18 02 17 and run the SCR efficiency test plan in ISTA, no DEF build up in the system, dispenses DEF within the 25-35g spec, NOx sensors are clean. I ran the entire test plan and the SCR catalyst passed, NOx sensors passed, EGT passed. I do not want to give back the vehicle until it's fixed.

1. The NOx sensors are the older versions that are prone to magnesium poisoning. I do not have any NOx codes whatsoever. Am I reading SI B01 10 17 correctly in that they will replace them under the extended warranty because they are the old P/N, but not setting NOx codes?

2. Guys that have replaced the SCR cat or run the test plan - what known good numbers should I be seeing after the test is run? I attached the results.

0
Matthew Mobile Technician
Bartlett, Illinois
Matthew
 

I have never worked on BMW, but there is an easy way I test NOx sensors. Disable the DEF doser and drive the vehicle looking at data. After the exhaust is warmed up and DEF consumed from SCR your NOx sensors should match pretty close to each other. 

+4 Ð Bounty Awarded
Brandon Technician
Medina, Minnesota
Brandon
 

The ISTA test plan accomplishes that on the lift, the entire test takes about 50 minutes to run autonomously. They did match each other during the catalyst prep part of the test.

+1 Ð Bounty Awarded
Matthew Mobile Technician
Bartlett, Illinois
Matthew
 

Okay, Cummins does something similar in their SCR test. 

+1 Ð Bounty Awarded
Stuart Owner/Technician
Prestonpans, United Kingdom
Stuart
 

Can you tell me what the acronym DEF is? Diesel Emission Fluid ?

0 Ð Bounty Awarded
Matthew Mobile Technician
Bartlett, Illinois
Matthew
 

Diesel Exhaust Fluid

0 Ð Bounty Awarded
Stuart Owner/Technician
Prestonpans, United Kingdom
Stuart
 

Thanks was just wanting to make sure we were on The same wavelength 👍

0 Ð Bounty Awarded
Brandon Technician
Medina, Minnesota
Brandon
 

Diesel Exhaust Fluid, Diesel Emissions Fluid, AdBlue, Urea Mixture, it's all the same.

0 Ð Bounty Awarded
Stuart Owner/Technician
Prestonpans, United Kingdom
Stuart
 

Thanks was just wanting to make sure we were on The same wavelength 👍

0 Ð Bounty Awarded
Nelson Manager
Huntington Beach, California
Nelson
   

Maybe i'm reading the graph wrong (it is late) but your 2nd graph shows the AFTER SCR NOx sensor reading higher than your BEFORE SCR NOx sensor. This should never happen. Usually a faulty dosing valve leaking raw urea into the exhaust system will do this (doubt it in this situation) or faulty NOx sensors. I wouldn't give that vehicle back to the customer without at least replacing BOTH NOx sensors since they are the older style. If you just replace 1 sensor, you will most likely get the same fault code again.

BTW 4D16 could be caused by a faulty NOx sensor just as a Catalytic Converter Efficiency fault code could be caused by a faulty O2 sensor on a gasser engine. 

BMW should cover the sensor replacements, just make sure the 4D16 fault is stored in the DDE when you take it to them.

I like that you did various drive cycles and tests since these diesels are notorious for logging completely different faults after replacing parts / clearing adaptations / drive cycles. 

+2 Ð Bounty Awarded
Brandon Technician
Medina, Minnesota
Brandon
 

I had the same thought until I looked closer, the lowest wavy green line is the pre-cat NOx, the top red flat line is the post-cat NOx. The blue line is the NOx ratio of before and after like a math channel.

I agree with not giving the vehicle back until it has at least 2 new NOx sensors, the big question is will BMW's extended warranty cover them IF there aren't any NOx fault codes, just SCR efficiency, or do we get to eat the $600 in sensors? I didn't really want to play the chicken and egg game with dealer without knowing for sure if they would be covered or someone has had it covered before.

0 Ð Bounty Awarded