About DieselCodes

What this site is

DieselCodes is a lookup and reference for the fault codes that trucks and their heaters report. It covers:

• J1939 codes: the SPN and FMI pair that most scanners show, with the standard meaning of each number;
• J1587-style codes, which are written as a control module (MID) plus a parameter (PID or SID) plus an FMI, used by some engines and other units;
• factory codes of individual makes, shown the way the make words them;
• fault codes of fuel-fired heaters, such as Webasto, Eberspächer and Planar.

Every code page ends with a verdict, Safe to drive or Do not drive, and says how much time you have and what happens if you keep going. The search on the home page also takes a whole fault list pasted from a scanner and shows which code is the likely root cause and which ones only followed it. How the verdict is reached is explained on How we decide whether you can keep driving.

Who it is for

• Drivers and owner-operators who see a lamp or a code on the roadside and need to decide what to do next.
• Fleet mechanics and dispatchers who want a quick, plain-language reading of a code before the truck reaches the yard.
• Anyone with a scanner reading who wants to know what the numbers mean.

It is a reference, not a workshop manual and not a diagnosis. The final call always belongs to a person who has the equipment to examine the truck.

Where the data comes from

• The standard. The meaning of SPN and FMI numbers follows the SAE J1939 standard. Code pages mark which reading comes from the J1939 standard and which from a make's own table.
• Factory tables. Make pages and code pages show how individual makes word their codes, taken from the factory tables of those makes. Where a make uses a number differently from the standard, both readings are shown.
• Manufacturer manuals. Heater pages are checked against manufacturer manuals and tables. The pages that give thresholds or procedures say that they follow the factory manual.
• Checking steps. The “what to check” steps are general guidance. They do not replace the workshop manual of your make, which the pages point you to.

Some fault names in the lookup tool come from factory tables that were compiled in another language and are translated, so a wording can look unusual. If it conflicts with the document of your manufacturer, the manufacturer's document is right. Not every code has its own page yet: the site grows page by page, and the date under each title shows when that page was last updated.

Who writes it

Pages are prepared and maintained by the DieselCodes editorial team. We do not publish individual author names, and no page claims the authority of a named person or a licence we do not hold.

Corrections

If you find a mistake, such as a wrong meaning of a code, a verdict that looks too relaxed or too strict, or a heater code that does not match your manual, please report it. Reports are checked against the manufacturer's documentation before a page is changed. A useful report names the page, the make and model, and the document that shows the correct value.

Send reports to info@dieselcodes.com.