This dag on Cummins isx 15 code1921 dpf full

[Nhramember]

Ok good morning everyone. I have been going thru it with this motor. It’s got 984000 on it. Most recently replaced 6 injector and the fuel pump head. Now the emission system is giving me code 1921. I have tried to regenerate the motor . It starts then halfway thru stops temps get about 700degrees then quits. I have an open emissions campaign to do from Cummins free. What could be causing this? Is def full? It’s saying 0.00 ash load. I also replace dpf sensor yesterday. I’m stumped. Thanks everyone.

[Rawze]

At 900,000+ miles?...

How old is the DPF and DOC elements?.

How old is the SCR element?.

When is the last time a full EGR tune-up was done on the engine side?.... all sensors replaced, pipes cleaned out?.. when is the last time the EGR cooler was removed and cleaned out thouroughly?.

All DPF problems are caused by the engine itself .. not the emissions systems.


When is the last time the NOx sensors, and other emissions system sensors, pipes, feed-tubers, decomp tube, elemnts removed and baked, de-ashed, flo-tested?.

Removing the DOC/DPF elements for cleaning and inspection + taking pictures of their faces and posting them here will reveal a lot about it (and the engine condition) too.

[Nhramember]

Just cleaned egr sensor had a lot of soot. Egr is about 1 1/2 old. Put new egr cooler summer 2022 and fall 2022 put doc and dpf on. I just did number 6 injector 2 weeks ago and just put the fuel pump head on just this week. I drove to Jacksonville Fla then I got this code. I’m just stumped rawze. Never had this since I owned the truck.

[Nhramember]

(12-30-2023 )Nhramember Wrote:  Just cleaned egr sensor had a lot of soot. Egr is about 1 1/2 old. Put new egr cooler summer 2022 and fall 2022 put doc and dpf on. I just did number 6 injector 2 weeks ago and just put the fuel pump head on just this week. I drove to Jacksonville Fla then I got this code. I’m just stumped rawze. Never had this since I owned the truck.

I’m doing a regen and it says this when doing the regen and stops. What’s causing this to stop the regen all is there.   

[Rawze]

Check the little tube and circuit for the exhaust pressure sensor on top of the thermostat. Make sure all sensors are also OEM only. Also check the sensors under the truck at the DPF, DOC, etc.

DOC missing is not a normal code to get when the system acts up.

Might also need to remove the DPF filter and see if it is actually clogging up like the alarm shows.

The engine is only going to last so long before it wears out to the point that it cannot keep those cans happy at some point.

Any regular coolant loss?... oil consumption?. etc?.

[Nhramember]

(12-30-2023 )Rawze Wrote:  Check the little tube and circuit for the exhaust pressure sensor on top of the thermostat. Make sure all sensors are also OEM only. Also check the sensors under the truck at the DPF, DOC, etc.

DOC missing is not a normal code to get when the system acts up.

Might also need to remove the DPF filter and see if it is actually clogging up like the alarm shows.

The engine is only going to last so long before it wears out to the point that it cannot keep those cans happy at some point.

Any regular coolant loss?... oil consumption?. etc?.

No coolant got a small leak under the bunk . I have a leak at the compressor but no oil consumption. Can bad def cause it to not regen to temperature?

[Bengy88]

(12-30-2023 )Nhramember Wrote:  

(12-30-2023 )Rawze Wrote:  Check the little tube and circuit for the exhaust pressure sensor on top of the thermostat. Make sure all sensors are also OEM only. Also check the sensors under the truck at the DPF, DOC, etc.

DOC missing is not a normal code to get when the system acts up.

Might also need to remove the DPF filter and see if it is actually clogging up like the alarm shows.

The engine is only going to last so long before it wears out to the point that it cannot keep those cans happy at some point.

Any regular coolant loss?... oil consumption?. etc?.

No coolant got a small leak under the bunk . I have a leak at the compressor but no oil consumption. Can bad def cause it to not regen to temperature?

Nope, def doesn’t have anything to do with a regen, def is sprayed into the scr catalyst not the dpf or doc, you really need to follow what Rawze told ya and then pull the dpf and doc to check for cracks, melting, elements being pushed, clogging etc. the temperature of your regen all depends on air flow in, fuel in, doc health, dpf health, and exhaust flow out.

[Rawze]

Also check for any exhaust leaks between back of engine and the Aftertreatment elements.

When is the last time the Doser injector behind the turbo was replaced or cleaned well. If the Doser injector is not spraying properly then it will not get up to temp too.

[PolishHammer]

Chekc the differential sensor tubes on the dpf make sure there not cracked or plugged look for a leak in between turbo to a doc and in between doc and dpf filter

This happens when the gaskets in between dpf are leaking and the dps throws a code