Originally Posted by Bigskiddy
Are we supposed to see a message when the regen is occurring? Mine never has.
Should the dealer be able to tell if any regens have occurred when they 'plug in their computer thingingy'.
Watching some Youtube vids on how DPF works, some have mentioned that due to the cleaner fuels and high temperature of a turbo diesel motor, a regen may not even occur or may only happen after a long amount of kms. Perhaps my constant highway driving and towing has taken a while to fill the filter.
I've probably watched a few of those same videos.
There's a very dry 25minute one with a old guy lecturing with presentation.
A couple of other from the UK design to help mechanics understand DPF were helpful.
This is what I got from them and some other reading:
If you are sitting idling or stop start traffic and doing short trips your exhaust will be too cool to burn any of the soot emission and it will accumulate in the DPF. 200-250C (?)
If you are driving along with the exhaust gases running hot enough to burn most of the soot in the emissions then the filter will stay pretty clear. This is called "passive regen" . No message here because the engine is just running normally, you just have the exhaust at the right temps. 350-400C
When the pressure sensors across the filter detect that the filter is becoming clogged past as certain value the PCM will decide it will have to burn it off to clear it. This is when the message you saw is displayed "Exhaust Filter .... Drive highway speeds" this is what they call an "Active Regen".
The EGR valve closes to 0%. - don't want any non combustibles cooling the chamber.
The fuel injectors sequence changes & injects a spray of fuel in the exhaust stroke, this fuel ignites in the exhaust system and raises the temperature dramatically. 700 C(?) (fuel consumption goes up too of course)
It also increase the turbo boost to compensate for power loss when doing it.
The drive at highway speeds thing is just so that you get cooling air flowing under the car because the exhaust is really hot.
Normally the differential pressure in the DPF should go down as it burn off the soot into ash and ejects it. I don't know if Jeep do the regen to the pressure diff or just on a max timeout?
If the "active regen" fails to clear the DPF as measured at the pressure differential. Then it goes into limp mode.
Something appears to be terribly wrong here in the software if you only get a few seconds from the "active regen" trigger to the "limp mode".
Is the trigger for the regen set at say... DP= 81%, and then when it starts it immediately monitors the DP for any increase at all (which might happen whilst cooking all that soot) and then throw limp mode?
The OBD thingingy would probably give the the codes raised in the PCM if they can see the history.
I don't know enough about OBD if the codes delete or clear themselves from the record.
OBDII has a standard set of codes. (hexidecimal). Whether all these codes are use i dont know.
The ones from P2452 to P246D are for the exhaust, DPF system & sensors.
Depends on how many pressur sensors there are and how many EGT sensors.
P2452-2456 is for the pressure diff sensor A
P2457 - is the EGR cooler
P2458 - is the regen duration - (too long?)
P2459 - regen frequency - (too frequent?)
P245A-P245D EGR bypass
P245E-P2462 pressure diff sensor B
P2463 - DPF soot accumulation
P2464 -P2465 pressure diff sensor
P2466-246A exhaust gas temp sensor faults
P246B - Vehicle Conditions Incorrect for Diesel Particulate Filter Regeneration
P246C - Diesel Particulate Filter Restriction – Forced Limited Power
P246D - pressure diff A/B correlation error
P246E onward - various Exh gas temp probe faults.
example P2463 | CAR OBD CODES
I'm thinking of buying an OBD dongle to monitor exhaust temps.
I dont think it can read the DPF %full as that is just a calculated value and there's no PID for that.
Pressure difference readings maybe? They would vary with gas flow though blocking so could only be compared checking the pressure at the same revs like at idle at different times.
Originally Posted by iboughtajeep
Has anyone tried a fast idle say 2000rpm for 15 min to see if it starts a regen?
It would not trigger it but once the car tells you its doing an active regen and to drive at highway speed, you could in theory pull over and run the car at elevated revs for that time (15min?) and keeping the exhaust flowing. The only thing is the exhaust will be roasting hot and there might be some visible ash coming out of the pipes. ( best to keep moving i think).
I have not had a DPF message (yet). When i do I think i'll panic and crap my pants