2018 Freightliner Cascadia - P207F Reductant Quality Performance keeping truck in derate

Question

My Cascadia with a DD15 engine keeps throwing P207F and I am currently stuck in a 5 MPH derate. The DEF tank is full of fresh fluid but the dash says poor quality detected and won't let me clear it with my generic scanner. I've already drained the tank once thinking it was bad fluid but it came back after 50 miles.

garagegrease · Accepted Answer

It turned out to be a failing Aftertreatment Device (ATD) NOx sensor on the outlet side, part number A0101532328. The sensor was reading 50ppm higher than actual, which tripped the P207F code. I replaced the sensor, performed a forced DPF regen, and then used DiagnosticLink to run the 'SCR Efficiency Test' which cleared the derate. Total cost for the sensor was about $550 and an hour of labor.

Ashley Park · Answer

Run a refractometer test on the fluid in the tank to be 100% sure. It should be exactly 32.5%. If the fluid is good, you likely have a crystalized decomposition pipe or a bad sensor.

Tom Patel · Answer

You need to check the NOx sensors before assuming it is the fluid. A skewed outlet NOx sensor will misread the conversion efficiency and the ACM will interpret that as bad DEF quality.

Sam Holloway · Answer

Check the DEF pump filter as well. If the pressure isn't consistent during the dosing cycle, it can cause an incomplete reaction that the computer flags as a quality issue.

2018 Freightliner Cascadia - P207F Reductant Quality Performance keeping truck in derate

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