Diagnostic Overview
Detroit SPN 2791 FMI 14 commonly indicates a special-instruction or manufacturer-specific EGR valve actuator fault. In practice, it often means the EGR actuator system has detected a control condition that does not fit a simple high/low signal failure. The code should be diagnosed with Detroit procedures and the exact engine serial number.
Likely Causes
EGR actuator internal fault, intermittent voltage drop, poor ground, wiring damage, connector corrosion, sticking EGR valve, or MCM/actuator communication issue.
What To Check First
Use DiagnosticLink troubleshooting, monitor actuator voltage and position, inspect grounds and connectors, wiggle-test the harness, and check the valve for mechanical binding. Verify final definition in Detroit DiagnosticLink because FMI meaning can vary by engine year, ACM/MCM calibration, and emissions level.