Diagnostic Overview
MaxxForce fault code SPN 3362 FMI 31 is generally associated with a DEF dosing system condition where the ECM has detected an abnormal state or condition present. In practical terms, the DEF system may not be able to dose, prime, purge, or prove operation correctly, which can contribute to SCR efficiency faults and inducement. This code should be diagnosed with all related DEF pressure, pump, doser, and quality codes.
Likely Causes
DEF pump problem, DEF pressure issue, plugged DEF filter, crystallized doser, contaminated DEF, frozen or restricted DEF line, wiring fault, or aftertreatment control module issue.
What To Check First
Check DEF quality, verify DEF pressure and pump command, inspect the doser and lines for crystallization, and review related SCR efficiency or DEF quality codes.