Diagnostic Overview
Detroit SPN 1118 FMI 16 is commonly associated with EGR temperature, EGR cooler performance, or an EGR-system condition above the normal range. The ECM may be seeing an EGR-related temperature or flow condition that is higher than expected. This can affect emissions, soot production, engine temperature, and derate strategy.
Likely Causes
Restricted EGR cooler, sticking EGR valve, carbon buildup, failed EGR temperature sensor, wiring issue, coolant flow problem through the cooler, or abnormal exhaust temperature.
What To Check First
Inspect EGR cooler flow and restriction, compare EGR temperature data, check sensor wiring, look for coolant or exhaust leaks, and verify EGR valve operation. Verify final definition in Detroit DiagnosticLink because FMI meaning can vary by engine year, ACM/MCM calibration, and emissions level.