Diagnostic Overview
Detroit SPN 5246 FMI 16 usually indicates an emissions inducement or derate condition at a moderate severity level. The truck may already be limiting power or preparing to impose a more serious speed or torque restriction. The underlying issue is usually another active aftertreatment or emissions fault.
Likely Causes
Unresolved DEF/SCR fault, DPF restriction, failed NOx sensor, poor DEF quality, DEF dosing issue, failed regen, or incomplete service routine after repair.
What To Check First
Pull the full active code list, repair the original emissions-system fault, confirm DEF and aftertreatment operation, and complete the required Detroit procedure to clear the inducement. Verify final definition in Detroit DiagnosticLink because FMI meaning can vary by engine year, ACM/MCM calibration, and emissions level.