Truck Fault Codes: J1939 SPN

Type the fault code your dash or scan tool gave you. Get a straight answer.

Truck Fault Codes is an offline reference for diesel truck fault codes. Enter an SPN, an SPN with an FMI, or an older J1587 code, and read what the parameter measures, what the failure mode means, the likely causes and what to check first - in workshop language.

WHAT IS INSIDE
- 8000+ J1939 SPN entries
- All 32 J1939 failure modes and the separate 16-mode J1587 table
- J1587 / J1708 lookup by MID + PID or SID + FMI, for older trucks
- Raw DTC byte decoder: four bytes to SPN, FMI and occurrence count
- PGN reference, including DM1 active and DM2 stored codes
- Source addresses: which module is reporting the fault
- Dash lamp meanings: amber, red, MIL and protect
- Symptom-first entry: white smoke, no start, derate, DPF, DEF and more
- Guides on derates, DPF regeneration, DEF and SCR, active and stored codes

WORKS WITH NO SIGNAL
Everything is on the phone. No account, no sign-in, no download on first use. It works in a yard, under a trailer, or on the hard shoulder with one bar.

40+ LANGUAGES
Explanations and the interface follow the language you pick, not just the menus.

BUILT FOR A WORKSHOP
Adjustable text size and a bold contrast mode, because this gets read in a dark bay with dirty hands.

WHAT IT DOES NOT DO
This is not a scan tool. It does not connect to your truck, it does not read codes from the ECU and it does not clear anything. You enter the code your dash or scan tool gave you, and the app explains it.

An independent reference, not affiliated with, endorsed by or sponsored by any vehicle or engine manufacturer. Always follow the manufacturer documentation for your vehicle, especially when a warning lamp indicates that the vehicle should be stopped.