fireman1073

i am getting upstream NOX sensor of SCR converter is not operational
and also downstream NOX sensor of SCR converter not operational

don't know what is causing this

both sensors bad? not likely

something else causing this?

i have a star c4 diagnostic but not sure what tests to run if someone has ideas or experience i would be grateful

Steve

Plutoe

Run the quick test and if you get faults double click the fault and follow the prescribed test\instructions!!

fireman1073

Pluto when i tried to run the tests it said
the NOx sensors must be operational
the fill level of the SCR catalytic converter must be lower than 0.05
neither of these are in spec for test and don't know how to proceed
how do i make the NOx sensors operational?
both of them stopped at the same time?
frustrating stupid government systems that won't stay working for more than 6 months
i should have ran from this vehicle
bought it in 7/15
replaced adblue heater$600.
replaced front strut 400.$
previous original owner spent thousands on oil cooler, other strut, airmatic system, battery draining, reflashing this and that etc. etc. etc.
ranting done

09 gl320 by the way

Plutoe

I'll do some research tonight and get back tomorrow, however in the interim post the fault code numbers!!

Post your VIN!!

dvdport

Which year is your car? I have a 2010 GL350 and had both NOx sensors in the convertor replaced at dealer's cost.

alx

Bad Nox sensors readings are common. Dealer would change them, an Indy would be well advised to remove them (very easy) and clean them. They do get dirty if you overfill with engine oil and/ or use inferior diesel fuel and/ or you don't do enough highway driving and roll on acceleration. If both are showing bad in DAS I would lean towards cleaning them. Btw Nox sensors are part of the emissions control and fall under the extended warranty. Depending on your year and mileage you might be able to replace them for free. Check with dealer.

fireman1073

4JGBF25EX9A503223 vin


i erased the codes just in case it was fuel related

from memory it was implausible signal from both NOx sensors

i did a visual on them but no obvious wire damage

it looks like someone has been in there because the plastic pan covering the electrical connectors were cracked from being pulled down and bolts were missing

when i find time i will remove and clean them

by the way how do i clean them? solvent? lightly brush them?

i assume they get carbon on them

thanks for the responses, i was feeling desperate and alone worrying about costs and taking it to the dealer

tight retirement budget, probably should have bought a more modest car but my mercedes in the past were easy to work on and bullet proof

83 300 sd, 84 300d, 97 s320, 95 300sd

all these made 200,000 miles and more and one was over 300,000 when i junked it and it still ran great

its the blutec crap and egr, dpf that kills these motors

thanks Steve

Plutoe

I think that you have a mess on your hands and with out a lift and tools you are handicaped, never the less I would check that the following emissions sensors are actualy connected--one, the upstream from SCR temp sensor--two, the SCR Frame module control unit--three, both Nox sensors are connected to their respective control unit.

Once you can confirm the above we can proceed!!

fireman1073

i have a lift and many tools so i checked the wires on above mentioned and all look ok, no damage,
i also removed the sensors and cleaned them but they were spotless already,

i also removed the def injector and inspected it, no crusty buildup

i tested pump with star tool---ok

i tried testing NOx sensors but scr catalyst had too much stuff in it to proceed
(i forgot the exact term the test said)
so i ran it to lower level in scr catalyst but was still too high
ran out of time but thats as far as i got.

i reset the two codes for nox sensor signal implausible and put in fresh fuel

600 miles later the codes came back (i checked with my cheap obd tool same codes)

going to plug in star tool and recheck to make sure of codes and attempt to run NOx sensor tests again


considering an emulator for bluetec so i can get inspection sticker for now

frustrated steve

fireman1073

did NOx sensor test,

communication error before 45 minute test ended but---

NOx sensor before scr catalyst not operational through whole test

NOx sensor after scr catalyst operational

so i think my problem is the front NOx sensor

alx

switch front with back and retest. you will get more decisive results and know which one is bad

fireman1073

Replaced the front NOx sensor, codes cleared, monitors set so I did the Massachusetts emissions test and it passed

$440 from the dealer

Easy to replace

Thanks