Diagnostic Overview
Detroit SPN 3246 usually relates to aftertreatment DPF outlet temperature or an exhaust temperature sensor signal used during regeneration. When this code is active, the engine controller may not trust the temperature reading needed to protect the DOC/DPF and manage regen strategy. A bad reading can cause failed regens, warnings, or derate depending on the related FMI and active companion codes.
Likely Causes
Failed DPF outlet temperature sensor, damaged sensor wiring, loose or corroded connector, exhaust leak near the sensor, incorrect sensor installation, or abnormal exhaust temperature during regen.
What To Check First
Compare cold sensor readings to ambient temperature, inspect the sensor and connector, check the harness near hot exhaust components, review active FMI, and verify regen temperature data in DiagnosticLink. Verify final definition in Detroit DiagnosticLink because FMI meaning can vary by engine year, ACM/MCM calibration, and emissions level.