Diagnostic Overview
Mack fault code P207F is commonly associated with reductant quality performance. The ECM may determine that DEF quality is poor or that NOx reduction is not matching expected DEF dosing. This can trigger SCR warnings and derate logic if not corrected.
Likely Causes
Contaminated DEF; diluted DEF; incorrect fluid in DEF tank; failed NOx sensor; DEF dosing issue; SCR catalyst problem; exhaust leak.
What To Check First
Test DEF concentration and contamination, inspect dosing operation, compare inlet and outlet NOx data, and check for exhaust leaks.