Diagnostic Overview
Detroit Flash Code 64 is an older Detroit/DDEC style code that can appear in turbo or engine-air-system diagnostics depending on configuration. In practical use, it should be mapped to the exact controller generation before diagnosing. If it is grouped under turbo, focus on air handling, turbo response, and related sensors.
Likely Causes
Turbo control issue, boost pressure sensor fault, charge-air leak, exhaust leak, intake restriction, older DDEC mapped condition, or wiring problem.
What To Check First
Use the engine serial number and DDEC/DiagnosticLink fault table to confirm the definition, then inspect the turbo system, charge-air piping, sensor circuits, and companion codes. Verify final definition in Detroit DiagnosticLink because FMI meaning can vary by engine year, ACM/MCM calibration, and emissions level.