Fault Code Lookup

Diagnostics

Look up an SAE J1939, FMI, or OEM fault code and get its meaning plus the first things to check.

Enter a fault code or keyword to search the database, or pick a brand to browse.

Not sure what to check first? Hand the result to the assistant.

Safety-critical: confirm before use

Torque, lifting, and load-chart values are safety-critical. Never operate from these figures alone. Confirm against the official manual and a qualified technician.

About this tool

Search a database of heavy-equipment fault codes and error codes: universal SAE J1939 SPN/FMI records plus brand-specific codes from Caterpillar, Komatsu, John Deere, Bobcat, JCB, Volvo, Cummins, and more. Enter a code or keyword, or narrow by brand and model.

If a code is not in the table, or you want it explained in plain English with the first things to check, hand it to the AI assistant.

Codes and steps are general guidance. Always confirm against the machine's manual before any repair, especially for derate, aftertreatment, and safety-related faults.

Frequently asked questions

What do SPN and FMI mean on a fault code?

On J1939 machines a fault code is an SPN (Suspect Parameter Number, what failed) plus an FMI (Failure Mode Identifier, how it failed). Together they describe the fault.

How do I look up a heavy equipment fault code?

Type the code as it appears - P0122, SPN 110 FMI 3, SID 4 FMI 3, or an OEM code like 08.1.F6 - or search plain keywords. Pick a brand and model to narrow the results.

What does engine derate mean on heavy equipment?

The ECU reduces power or speed to protect the engine or aftertreatment, often for DEF/SCR or DPF faults. Address it promptly to avoid a further shutdown.

Fault and error code guides by brand

In-depth, plain-English write-ups for manufacturer fault codes and error codes, with meanings, common causes, and first checks.