ISX cm2350 low. power/poor. Fuel milage.

[DPS567180]

(03-15-2025 )JimT Wrote:  Yet another thought as i read through this thread again. You mentioned DEF light. When was the last time you changed the DEF filter? Also, has there been any codes in the ECM related to the DEF light? The entire aftertreatment system has to be working properly and balanced. If one part isn't functioning properly (or just one sensor reading incorrectly) it can throw off the entire system and cause all kind of power loss issues, many which aren't reported because they aren't faults, just the ECM adjusting operation to try to balance things out, so to speak. Perhaps a deeper dive with CT might be able to spot something? I'm speculating here since I've never personally used it.

Poor DEF quality could play a role. The quality of at-the-pump DEF is known to be variable. Maybe try switching to boxed DEF for a while and top it off every time you fuel up. If after a few weeks things magically get better then you'll know why.

Also, just because you replaced the DEF doser doesn't mean it fixed the problem or that the new doser was any good. Sad, but something to consider.

I'll be inspecting everything when I get home next weekend. I was supposed to clean my EGR cooler last time but my gaskets didn't show up in time so I'm doing it this upcoming weekend. I also got a code 1894 for actuator abnormal update rate. I'm going to do the electrical testing when I get home as well to verify it's the actuator. Thanks for reminding me about my DEF filter. I bought it about a year ago and planned on replacing it but I had a personal family crisis and completely forgot about it until it was just mentioned. I'll also be doing that.. It looks like me and my exhaust side of my truck are going to get to know each other very well. Lol