Freightliner Fault Codes — Complete Guide

Freightliner SPN/FMI codes cover Cascadia DD13/DD15, M2 Business Class. This hub lists 35 diagnostic pages with symptoms, ranked causes, scan-tool steps, and 2026 repair costs — use INSITE, DiagnosticLink, or EST depending on your engine family.

By Professional Diesel Repair TeamPublished: January 2026Last updated: September 2026

How We Tested and Verified

Freightliner fault code definitions cross-checked against SAE J1939-71 and Freightliner OEM service bulletins. Diagnostic tips validated by field technicians September 2026.

Freightliner Engine Platforms

Freightliner engines covered on this site include: Cascadia DD13/DD15, M2 Business Class. Diagnostic procedures vary by platform — always verify against your specific engine serial number and calibration.

Most Common Freightliner Fault Codes

Code	Component	Severity	Definition
SPN 111 FMI 1	Engine Coolant Level Sensor	Critical	Engine Coolant Level - Data Valid But Below Normal Operating Range
SPN 190 FMI 0	Engine Speed Sensor Circuit	Critical	Engine Speed - Data Valid But Above Normal Operational Range
SPN 5246 FMI 31	SCR Operator Inducement	Critical	Aftertreatment 1 SCR Operator Inducement - Severe Level
SPN 630 FMI 12	ECM Calibration Memory	Critical	Calibration Memory - Bad Intelligent Device or Component
SPN 641 FMI 5	Variable Geometry Turbocharger Actuator #1	Critical	VGT Actuator #1 - Current Below Normal or Open Circuit (FMI 5)
SPN 100 FMI 1	Engine Oil Pressure	High	Engine Oil Pressure — Data Valid But Below Normal Operating Range - Most Severe Level
SPN 100 FMI 3	Engine Oil Pressure Sensor Circuit	High	Engine Oil Pressure - Voltage Above Normal, Circuit Shorted High
SPN 1127 FMI 3	Turbocharger 1 Boost Pressure Sensor	High	Turbocharger 1 boost pressure sensor signal voltage is above normal — FMI 3 high-voltage fault indicating a short to supply voltage or open sensor ground
SPN 157 FMI 1	Injector Metering Rail 1 Pressure	High	Engine Fuel 1 Injector Metering Rail 1 Pressure - Data Valid But Below Normal Operational Range - Most Severe Level
SPN 168 FMI 4	Battery / ECU Power Supply Voltage	High	Electrical Potential (Voltage) - Voltage Below Normal, or Shorted to Low Source
SPN 3464 FMI 10	Aftertreatment SCR Catalyst	High	Abnormal Rate of Change in SCR Catalyst Temperature
SPN 3509 FMI 14	Sensor Supply Voltage 1	High	Sensor Supply Voltage 1 - Special Instructions
SPN 3509 FMI 16	Sensor Supply Voltage 1	High	Sensor Supply Voltage 1 - Data Valid But Above Normal Operating Range
SPN 4364 FMI 18	SCR NOx Conversion Efficiency	High	Aftertreatment 1 SCR Catalyst Conversion Efficiency - Data Valid But Below Normal Operational Range - Moderately Severe Level
SPN 636 FMI 2	Crankshaft Position Sensor	High	Engine Position Sensor - Data Erratic, Intermittent, or Incorrect
SPN 639 FMI 9	J1939 Data Link (CAN Network #1)	High	J1939 Network #1 - Abnormal Update Rate
SPN 641 FMI 7	VGT Actuator	High	Variable Geometry Turbocharger Actuator - Mechanical System Not Responding
SPN 646 FMI 14	Wastegate Drive	High	Engine Turbocharger 1 Wastegate Drive - Special Instructions
SPN 651 FMI 5	Cylinder 1 Injector	High	Engine Injector Cylinder 1 - Current Below Normal or Open Circuit
SPN 653 FMI 6	Injector Cylinder 3	High	Engine Injector Cylinder #3 - Current Above Normal or Shorted Circuit

Freightliner-Specific Diagnostic Tips

Freightliner fault codes route through the engine OEM — identify engine first, then use correct scan tool.
Cascadia SAM (Signal Acquisition Module) CAN faults can mask engine codes; check SAM voltage first.
Check chassis harness grounds at left frame rail when multiple modules lose communication.