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Detroit DD15 Fault Codes — Top 30 SPN/FMI Codes

The Detroit DD15 is the flagship engine for Freightliner Cascadia trucks. This reference covers the 30 most frequent SPN/FMI fault codes with symptoms, causes, and step-by-step diagnostic procedures using DDDL and standard tools.

Detroit DD15J1939 SPN/FMI30 Fault Codes

Fault Codes Covered

System Categories

Critical Faults

Aftertreatment Codes

Detroit DD15 Engine Overview

Engine Specifications

Displacement14.8L (903 cu in)
ConfigurationInline 6-cylinder
Power Range455–560 HP
Torque Range1,550–1,850 lb-ft
Emission StandardEPA 2010+ / GHG17
AftertreatmentDPF + SCR + DEF

Common Applications

Freightliner Cascadia (primary application)
Western Star 5700XE
Long-haul and regional trucking
Tanker and flatbed applications

Top 30 Detroit DD15 Fault Codes

Click any fault code for full diagnostic procedures, wiring tests, and repair steps.

SPN	FMI	Description	System	Severity
157	18	Fuel Rail Pressure — Low (Moderate)	Fuel	High
157	1	Fuel Rail Pressure — Low	Fuel	High
3031	0	DPF Soot Load — High	Aftertreatment	High
4364	18	SCR Efficiency — Below Threshold	Aftertreatment	High
5246	31	DEF Dosing Agent Concentration — Low	Aftertreatment	High
3216	2	SCR Inlet NOx — Erratic	Aftertreatment	High
3226	2	SCR Outlet NOx — Erratic	Aftertreatment	High
110	0	Engine Coolant Temperature — High	Cooling	Critical
100	1	Engine Oil Pressure — Low	Lubrication	Critical
102	1	Intake Manifold Pressure — Low	Turbo/Air	High
1189	7	VGT Actuator — Mechanical Not Responding	Turbo/Air	High
3480	5	HC Doser — Current Below Normal	Aftertreatment	High
3484	31	Aftertreatment Regeneration Inhibited	Aftertreatment	Medium
3232	18	SCR Efficiency — Below Threshold (Severe)	Aftertreatment	Critical
3230	0	SCR Operator Inducement — Severity 2	Aftertreatment	Critical
636	2	Camshaft Speed/Position — Erratic	Engine	High
637	2	Crankshaft Speed/Position — Erratic	Engine	High
105	0	Intake Manifold Temperature — High	Turbo/Air	High
101	0	Crankcase Pressure — High	Engine	High
175	0	Engine Oil Temperature — High	Lubrication	High
94	1	Fuel Delivery Pressure — Low	Fuel	High
97	0	Water in Fuel — High	Fuel	High
1079	3	Sensor Supply Voltage 1 — High	Electrical	High
639	9	J1939 Network — Abnormal Update Rate	Electrical	High
1109	31	Engine Protection System — Shutdown	Engine	Critical
1111	31	Engine Protection System — Derate	Engine	High
3360	4	DEF Tank Level — Voltage Below Normal	Aftertreatment	High
3490	4	DEF Heater — Voltage Below Normal	Aftertreatment	High
167	1	Battery Voltage — Low	Electrical	High
1640	7	Fan Clutch — Mechanical Not Responding	Cooling	High

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