Paccar PX8 2008 ISC315 code SPN 3251-FMI0 DPF is good, serviced and tested, the pressure sensor is good, will not regenerate. Any suggestions
Good luck. We have members on here who talk about the minutiae of all the older engines but I have seen precious little about these new emissions systems. What little manuals I have seen seem to be written for dummies, and if the problem isn't simpler than changing a fuse then the answer is to take it to the dealership who may or may not be able to do anything with it on the 1st, 2nd, 3rd try. It is all a black box and we are not allowed to know anything about it. That being said, what do you mean that the DPF is good, serviced and tested? If it was just run on a cleaning machine, how do we know it is not partially plugged with something other than soot causing the pressure drop to still be high?
I had the DPF cleaned, baked and tested at a dealer.
I don't know what the pressure drop is supposed to be but can you hook up an external gauge across the DPF and see what the actual drop is vs when the computer sets a code? I am guessing that the dealer clean-out did not get it really all that clean.
I have had issues getting a dpfs cleaned, they never seem to get as good as a new one. When you say it wont regen, does it throw this code and quit the regen? Or is the code active as soon as you start the engine? I dont know how good your scanner is, but can you pull up the freeze frame data and see what the pressure was when the code logged? If not can you at least monitor the sensor and see what the readings are? Most of the time its a wiring issue. If you have high resistance on the sensor signal/return wires the ecm will not be getting a true reading of the sensor. What chassis is it in? Got any accel pedal faults? Accel pedal and dpf pressure sensor share the same power.
The code is active as soon as you start the engine. My scanner is not good enough to display the sensor data. The 5 volt signal to the sensor is good, the signal wire is .72 volts at idle, voltage rises to .76 volts at the limited 1500 RPM, this is at the sensor. The chassis is a 2008 Kenworth.
What I am struggling with is: I have a code SPN 3251-FMI0, is there no way to get information on exactly what is causing this code?
I did a quick search for SPN 3251 and they seem to indicate it is pressure sensor reading erratic or incorrect. This would explain why it will not regenerate if it cannot trust the sensor. How do you know the sensor is good? What does the manual say about this situation, testing the sensor and such? And of course there is always the possibility of following out the wires back to the ECM although in modern times they rarely seem to have trouble.
Sensor is new, looking for a schematic to check wiring, that's where i am now.
Whats the s/n of your engine. I can get you the cummins side diagram.
Also have you even been able to clear the code?? There is a high chance your scanner will not work. On the oem cummins program you have to reset the aftertreatment and program in a cleaned dpf before it will let you clear that code. Possible that you fixed the cel already and just dont have the abililty to clear the code
Engine Number 46739547
Here's after treatment wiring
can get you more diag if the wiring checks out, definitely check that interface plug, like a 10-12 port connector on intake side of motor
i got a set of new injectors for this engine make offer
Solved! Found a friend with Cummins Insight software, we were able to force regen through the software. Once we did that the code disappeared. Thanks for all the help!!