Cummins ISX15 Fault Codes

Complete diagnostic trouble code reference for the Cummins ISX15 heavy-duty diesel engine. 8 fault codes • Protocols: J1587, J1939

🔧 Engine Context: The Cummins ISX15/X15 series is the most common heavy-duty diesel engine in North America, powering Freightliner Cascadia, Kenworth T680, and Peterbilt 579 trucks. Introduced in 2007, the ISX15 has gone through multiple emissions control iterations — from EGR-only to SCR+DEF. Each iteration introduced new fault codes. The most common issues on this series include VGT turbo actuator failures, EGR system problems, and engine protection derate events.

SPN 1569 FMI 31

Engine Protection Torque Derate

Component: Engine Control Module (ECM) • J1939 SPN:1569 FMI:31

🔴 STOP ENGINE

SPN 102 FMI 18

Intake Manifold Pressure critically low

Component: Turbocharger / Charge Air System • J1939 SPN:102 FMI:18

🔴 STOP ENGINE

SPN 111 FMI 18

Engine Coolant Level critically low

Component: Coolant Level Sensor / Cooling System • J1939 SPN:111 FMI:18

🔴 STOP ENGINE

SPN 639 FMI 9

J1939 CAN Bus Communication Loss

Component: Engine Control Module / CAN Bus • J1939 SPN:639 FMI:9

🔴 STOP ENGINE

SPN 1322 FMI 31

Misfire Detected on Cylinder 6

Component: Cylinder 6 Injector / Valve Train • J1939 SPN:1322 FMI:31

🟡 CHECK AT NEXT STOP

MID 128 SID 1 FMI 5

Injector Cylinder 1 Circuit

Component: Fuel Injector #1 Solenoid Circuit • J1587 MID:128 PID:

🟡 CHECK AT NEXT STOP

SPN 191 FMI 16

Transmission Output Shaft Speed

Component: Transmission Output Speed Sensor (TOSS) • J1939 SPN:191 FMI:16

🟡 CHECK AT NEXT STOP

MID 128 PID 102 FMI 3

Boost Pressure Sensor

Component: Intake Manifold Pressure Sensor • J1587 MID:128 PID:102

🟠 CHECK SOON

Engine Series Coverage: Cummins ISX15 engine specifications and fault codes sourced from SAE J1939/J1587 public standards and OEM technical service documentation. Last reviewed 2026-07-06T15:05:01Z.