Cummins · X15 / ISX15SPN 4364 FMI 18
SCR NOx conversion efficiency low
Check DEF quality, dosing and NOx sensors.
Diagnostic error codes
Quick operational guidance. Always confirm codes with OEM diagnostics before repair.
High
Cummins · X15 / ISX15SPN 520372 FMI 16
DPF soot level elevated
Schedule parked regeneration and inspect restriction.
Cummins · X12 / X15SPN 1569 FMI 31
Engine protection torque derate active
Read the companion fault and correct the root cause before continuing.
Cummins · X12 / X15SPN 5246 FMI 0
Final inducement active
Service the DEF and aftertreatment fault immediately.
Detroit · DD13 / DD15 / DD16SPN 102 FMI 18
Intake manifold pressure below expected
Inspect charge-air piping, clamps, turbo and pressure sensor.
Detroit · DD13 / DD15 / DD16SPN 4364 FMI 1
SCR conversion efficiency below threshold
Check DEF dosing, leaks and inlet/outlet NOx sensor values.
Detroit · DD13 / DD15 / DD16SPN 3251 FMI 0
DPF differential pressure high
Inspect DPF restriction and differential pressure tubes before regeneration.
PACCAR · MX-11 / MX-13SPN 94 FMI 1
Fuel delivery pressure low
Check fuel level, filters, restriction and supply pressure.
PACCAR · MX-11 / MX-13SPN 110 FMI 0
Engine coolant temperature high
Stop safely and inspect coolant level, fan operation and leaks.
PACCAR · MX-11 / MX-13SPN 3226 FMI 10
Outlet NOx sensor response abnormal
Inspect wiring and compare commanded and measured NOx values.
All makes · J1939SPN 639 FMI 9
J1939 network communication issue
Inspect power, grounds, terminating resistance and CAN wiring.
All makes · DieselSPN 111 FMI 1
Engine coolant level low
Stop safely, inspect for leaks and top up only when cool.
All makes · ElectricalSPN 168 FMI 4
Battery voltage below normal
Test batteries, alternator and cable connections.
All makes · DieselSPN 100 FMI 1
Engine oil pressure low
Shut down when safe and verify oil level and mechanical pressure.