excessive regen cycles 14.9L ISX 2008 volvo

It all started when I got this truck, a 2008 Volvo 670 with 14.9 Cummins ISX, almost constant regeneration cycles lasting 30-45mins with maybe 30min breaks in between. Have had the DPF cleaned and ash burned out, but still regens on the same cycle.

Every so often a Volvo OEM fault code of MID 128 SID 360(380?) FMI 11 pops up active, but goes inactive after a while and the constant regens resume. Does not regen when the fault code is active.

Almost zero oil consumption, maybe half a gallon every 10k miles. Zero coolant consumption, and no check engine light, ever.

Fuel mileage is normal, I haul max weight up steep hills pretty often, about 6.6mpg, maybe a little less.

Everything functions normally, however if this is indicative of a problem I would like to have it fixed now instead of it bankrupting me down the road.

Ive been thinking maybe one of the sensors in the DPF is going bad/in the wrong place.

Just wondering if anyone else may have some insight into what is causing this and/or suggestions on what to check? Any advice/ideas would be welcome. The cheaper the better

 

the mechanic said they cleaned the 7th injector when they took the DPF off for cleaning, however the pressure sensor sounds like a good idea, should have mentioned the 7th injector was cleaned, thats my fault.

Also, I just found out from cummins about 30 mins ago that the cummins fault code that corresponds to that Volvo OEM code is 1664 Catalyst Missing - Condition Exists. The code only goes active from time to time though. Does this make any sense to you at all?

 

i guess not...

 

Thanks for your replies guys, I definitely have a better idea of how the aftertreatment system works now that you guys broke it down for me.
Im thinking since the 7th injector could cause both of my problems, I'm going to have that checked first, and if that checks out then move to the DOC & sensors.
Thanks for your replies guys will keep updated on what I found out so maybe someone else reading this with similar symptoms can save themselves some $$$$

 

so i finally decided to take it to the shop, shame on me. Had other stuff to get done so I decided to have them check out the regen issue. I wish I would have left well enough alone.

they checked the dpf and catalyst, neither looked in great shape but they were ok for now. they checked all the sensors, seemed to be working fine. Flow tested 7th injector and it read 1.7 ml(?) when it should have been at 4. Does this sound right?

replaced the 7th injector, cleaned catalyst and dpf. So I'm going down the road happy because Im thinking all my problems are solved. Nope, on a 300 mile trip I ran 6 regen cycles before the fault came up and it didnt regen at all after that. Noticed a power gain when the fault code went active aswell. No check engine light or anything. But I guess I know it wasnt the 7th injector now I guess.

Any other ideas? Im kind of thinking I'm just going to run it until a real problem presents itself, done dumping money into the truck trying to get this emissions stuff to work right.

 

i see what you were saying there. also in the 2nd link the map of the cummins engine is extremely helpful in figuring out what some of this is.

btw I disabled regen all day today and didnt get the "regen needed" warning,check light, or anything, just ran a manual one at the end of the day. So if its not filling up I wonder why it goes into so many regens on its own during my trip if I let it. Considering just running a manual one at the end of every day.

next thing up is checking that differential sensor in the dpf.