code 3251.0

[davidjrawls]

2014 freightliner cascadia 125dc cm2250 isx Getting code 3251.0 Dpf Differential pressure Data valid but above normal operation range with red engine stop light on. truck had previously been running fine no codes or lights but fuel mileage seemed low. When I went to use truck about 3 weeks ago had an engine light upon startup so I pulled codes and it showed injector 6 code and aftertreatment pressure sensor code I cleared them and they didn't come back so went ahead using truck for couple days with no problems. I had ordered an imap sensor, egr differential pressure, and the exhaust backpressure sensor per the egr tune up videos I had watched on this forum. Was going to used truck today so decided to replace sensors before I did. Changed all three sensors and started truck everything seemed fine let it idle in farm yard about and hour while I was loading trailer. Took off down road and immediately when truck would start to pull and build boost then would loose power and sounded late a waste gate opening and dumping the boost. So I pulled over and looked at everything under hood and couldn't find anything obvious. So decided to ease on up the road to a better spot to pull off. Before I got to spot had engine light on. when I got there pulled codes and had a turbo actuator code and dpf code. cleared coded and the turbo code didn't return. but the 3251 code would not clear even with the engine off. then I noticed some black soot around the egr diff pressure sensor so I changed it back to the old one and also changed the back pressure sensor back to the old sensor as the new ones I got were not Cummins original ones like I thought I was ordering. still code was there and engine was in derate. I then removed the tubes from the dpf dif pressure sensor and tried to clear code with engine off and soon as light went out it came back on. So I unplugged the sensor and tried to clear code thinking it would give me a different code but still gave me same code that wouldn't clear. Also I don't have insite just a cheap code scanner.