Engine fault codes
The air path and the cylinders: turbo boost and VGT position, intake and charge-air temperature, mass airflow, the intake-air heater and glow plugs, crank and cam position, and the engine-protection logic that pulls power when a reading goes out of range. EGR is not here — it is under Aftertreatment. A single sensor fault in this list usually shows up as low power long before anything actually fails.
All 58 engine SPN/FMI and OBD codes in the knowledge base are listed below — each with what it means, how serious it is, the most-likely causes, and what to check first.
Engine codes (58)
Other systems
Cooling, lubrication, HVAC and chassis/cab codes are listed on the fault code lookup, along with the search box that covers every code.
General diagnostic guidance for heavy-duty diesel equipment (Cummins, Detroit, PACCAR, Volvo, Mack and more). Not a substitute for a scan-tool diagnosis on your specific truck.