Caterpillar Fault Codes — Complete Guide

Caterpillar SPN/FMI codes cover C15, C13, C7 and 1 more platforms. This hub lists 34 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

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

Caterpillar Engine Platforms

Caterpillar engines covered on this site include: C15, C13, C7, C9. Diagnostic procedures vary by platform — always verify against your specific engine serial number and calibration.

Most Common Caterpillar Fault Codes

Code	Component	Severity	Definition
SPN 100 FMI 1	Engine Oil Pressure Sensor	Critical	Engine Oil Pressure - Data Valid But Below Normal Operational Range
SPN 110 FMI 0	Engine Coolant Temperature Sensor	Critical	Engine Coolant Temperature - Data Valid But Above Normal Operating Range - Most Severe Level
SPN 164 FMI 0	Fuel Injection / Rail Pressure	Critical	Injection Actuation Pressure / Fuel Rail Pressure - Data Valid But Above Normal Operating Range
SPN 190 FMI 0	Engine Speed Sensor Circuit	Critical	Engine Speed - Data Valid But Above Normal Operational Range
SPN 190 FMI 8	Engine Speed (Crankshaft Position)	Critical	Engine speed signal abnormal frequency — the crankshaft position sensor is producing a signal outside the expected frequency range for the measured operating condition.
SPN 3246 FMI 16	DPF Outlet Gas Temperature Sensor	Critical	Aftertreatment 1 Diesel Particulate Filter Outlet Gas Temperature - Data Valid But Above Normal Operating Range
SPN 94 FMI 1	Fuel Delivery Pressure Sensor	Critical	Engine Fuel Delivery Pressure - Data Valid But Below Normal Operational Range - Most Severe Level
SPN C15-REGEN FMI N/A	Caterpillar C15 ACERT DPF Regeneration	High	DPF regeneration issues on Caterpillar C15 ACERT engines — soot loading, regen inhibit, exhaust temperature, and differential pressure faults
SPN 101 FMI 16	Engine Crankcase Pressure	High	Engine Crankcase Pressure - Data Valid But Above Normal Operating Range - Moderately Severe
SPN 110 FMI 16	Engine Coolant Temperature Sensor	High	Engine Coolant Temperature - Data Valid But Above Normal Operational Range - Moderately Severe Level
SPN 1127 FMI 14	Turbocharger 1 Boost Pressure	High	Engine Turbocharger 1 Boost Pressure - Special Instructions
SPN 1381 FMI 1	Fuel Supply Pump Inlet Pressure Sensor	High	Engine Fuel Supply Pump Inlet Pressure - Data Valid But Below Normal Operational Range - Most Severe Level
SPN 168 FMI 1	Battery / ECU Power Supply Voltage	High	Electrical Potential (Voltage) - Data Valid But Below Normal Operating Range
SPN 190 FMI 2	Crankshaft Position Sensor	High	Engine Speed - Data Erratic, Intermittent, or Incorrect
SPN 3363 FMI 1	DEF Pump Pressure Sensor	High	Aftertreatment 1 Diesel Exhaust Fluid Pump Pressure - Data Valid But Below Normal Operational Range - Most Severe Level
SPN 3364 FMI 9	DEF Quality Sensor	High	Aftertreatment 1 DEF Tank - Liquid Quality Parameter - Abnormal Update Rate
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 4766 FMI 16	DOC Outlet Gas Temperature Sensor	High	Aftertreatment 1 Diesel Oxidation Catalyst Outlet Gas Temperature - Data Valid But Above Normal Operational Range - Moderately Severe Level
SPN 637 FMI 2	Camshaft/Timing Reference Sensor	High	Engine Timing Sensor - Erratic, Intermittent, or Incorrect
SPN 646 FMI 3	Wastegate Drive	High	Engine Turbocharger 1 Wastegate Drive - Voltage Above Normal

Caterpillar-Specific Diagnostic Tips

Cat ET (Electronic Technician) shows HEUI injector actuation pressure in real time.
C15 ACERT turbo boost leaks cause low-power complaints before any fault code sets.
Verify 8-pin throttle pedal connector integrity — broken locking tabs are the #1 APS fault.