Machinery & Forklift Fault Codes, With Sources
Your display shows a code. We tell you what it means, what to check first, and where the information came from — compiled from factory manuals and public service documentation, never guessed. Currently 191 codes across Caterpillar and Curtis controllers, plus the full J1939 FMI reference. More brands are added as their data is verified.
Curtis Controllers
47 codes for 1234 / 1236 / 1238 controllers — the controllers inside many electric forklifts.
Browse Curtis codes →J1939 / FMI Reference
The standard FMI table (0–31) behind Cummins, CAT and most electronic engines.
Open the FMI table →How a fault code works
An electronic control unit watches sensors and circuits. When something is out of range it stores a code: which component (CID / SPN / controller code number) and how it failed (the FMI). Two machines can show similar numbers with different meanings, which is why every page here names its source and the exact system it applies to.