Kenworth Fault Codes — Complete Guide

Kenworth SPN/FMI codes cover T680 PACCAR MX-13, W900 Cummins X15. This hub lists 24 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

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

Kenworth Engine Platforms

Kenworth engines covered on this site include: T680 PACCAR MX-13, W900 Cummins X15. Diagnostic procedures vary by platform — always verify against your specific engine serial number and calibration.

Most Common Kenworth Fault Codes

Code	Component	Severity	Definition
SPN 100 FMI 1	Engine Oil Pressure Sensor	Critical	Engine Oil Pressure - Data Valid But Below Normal Operating Range - Most Severe Level
SPN 110 FMI 0	Engine Coolant Temperature Sensor	Critical	Engine Coolant Temperature - Data Valid But Above Normal Operating Range - Most Severe Level
SPN 157 FMI 1	Fuel Rail Pressure	Critical	Engine Fuel 1 Injector Metering Rail 1 Pressure — Data Valid But Below Normal Operating Range - Most Severe Level
SPN 100 FMI 0	Engine Oil Pressure	High	Engine Oil Pressure — Data Valid But Above Normal Operating Range - Most Severe Level
SPN 157 FMI 18	Fuel Rail Pressure Sensor	High	Engine Injector Metering Rail 1 Pressure - Data Valid But Below Normal Operational Range - Moderately Severe Level
SPN 168 FMI 0	Battery / Charging System Circuit	High	Electrical Potential (Voltage) - Data Valid But Above Normal Operating Range - Most Severe Level
SPN 172 FMI 16	Engine Air Inlet Temperature Sensor	High	Engine Air Inlet Temperature - Data Valid But Above Normal Operating Range
SPN 2659 FMI 7	Turbocharger Wastegate Actuator	High	Turbocharger Wastegate - Mechanical System Not Responding
SPN 3226 FMI 16	Outlet NOx Sensor	High	Selective Catalytic Reduction NOx Efficiency Low - Data Valid But Above Normal Operational Range - Moderately Severe Level
SPN 4094 FMI 16	DPF Soot Load	High	Aftertreatment 1 Diesel Particulate Filter Soot Load Percent - Data Valid But Above Normal Operational Range - Moderately Severe Level
SPN 4363 FMI 16	SCR Outlet Gas Temperature	High	Aftertreatment 1 SCR Catalyst Outlet Gas Temperature - Data Valid But Above Normal Operational Range - Moderately Severe Level
SPN 636 FMI 3	Crankshaft Position Sensor	High	Engine Position Sensor - Voltage Above Normal or Shorted to High Source
SPN 637 FMI 4	Engine Timing / Cam Position Sensor	High	Cam position sensor signal voltage below normal — FMI 4 low-voltage fault on the camshaft timing sensor circuit.
SPN 646 FMI 7	Turbocharger Wastegate Drive	High	Engine Turbocharger 1 Wastegate Drive - Mechanical System Not Responding or Out of Adjustment
SPN 652 FMI 6	Injector Cylinder 2	High	Injector Cylinder 2 - Current Below Normal
SPN 91 FMI 3	Accelerator Pedal Position Sensor Circuit	High	Accelerator Pedal Position 1 - Voltage Above Normal, Circuit Shorted High
SPN 102 FMI 10	Boost Pressure	Medium	Engine Intake Manifold #1 Pressure — Abnormal Rate of Change
SPN 108 FMI 3	Barometric Pressure Sensor	Medium	Barometric Pressure Sensor - Voltage Above Normal, Or Shorted To High Source
SPN 110 FMI 2	Engine Coolant Temperature	Medium	Engine Coolant Temperature 1 — Data Erratic, Intermittent, or Incorrect
SPN 1382 FMI 1	Fuel Filter Suction Side Differential Pressure	Medium	Fuel filter suction-side differential pressure reading is below normal operating range — sensor failure or wiring fault rather than an actual filter restriction

Kenworth-Specific Diagnostic Tips

Kenworth trucks carry PACCAR, Cummins, or Detroit engines — read the data plate before diagnosing.
T680 dash cluster CAN gateway issues can block ECM communication on some MY2018–2020 builds.
PACCAR MX-13 on Kenworth uses the same EST procedures as Peterbilt.