Diagnostic Overview
Detroit SPN 2791 FMI 11 commonly relates to EGR valve actuator or EGR valve control performance. The ECM is seeing that the EGR actuator is not behaving as expected or the valve position does not match the command. This can cause rough running, derate, poor throttle response, or emissions faults.
Likely Causes
Failed EGR actuator, sticking EGR valve, carbon buildup, poor actuator connector contact, wiring fault, low voltage supply, bad ground, or controller signal issue.
What To Check First
Run an EGR actuator test, inspect the actuator connector and harness, verify power and ground, check for carbon binding, and compare commanded versus actual EGR position. Verify final definition in Detroit DiagnosticLink because FMI meaning can vary by engine year, ACM/MCM calibration, and emissions level.