What does this code mean?
The wording below belongs to the named make and communication. Match the complete code, reporting module, model year and engine before applying it.
A code identifies a detected condition, not a part that must automatically be replaced.
Manufacturer wording
Source wording can vary by vehicle and suffix. It is shown as written, not as a universal diagnosis.
P3859MX ENGINEManufacturer communications
2Original wording in English
KENWORTH
Reported code forms P3859
KENWORTH: SOME VEHICLES HAVE DEF LINES ROUTED INCORRECTLY. ERROR CODES P3859 (MX ENGINE) AND P3568 (CUMMINS), DEF DOSER IS NOT RESPONDING OR IS OUT OF ADJUSTMENT FAULT. MODEL INCLUDES T660/T700 AERO MANUFACTURED…
KENWORTH
Reported code forms P3859
KENWORTH: SEE DOCUMENT SEARCH BUTTON SEARCH BUTTON FOR OWNER LETTER. DUE TO DEF DOSER NOT RESPONDING OR IS OUT OF FAULT ADJUSTMENT, THE COOLANT LINES (CROSSOVER EXHAUSTS) ARE ROUTED INCORRECTLY, IN SOME CHASSIS, AND MAY…
Check vehicle applicability
1A listed vehicle is a research lead. Confirm the engine, production range and software in the manufacturer's information.
| Make | Model | Model year |
|---|---|---|
| Kenworth | KENWORTH | Year not specified |
Before replacing a part
Record codes and freeze-frame data. Check battery condition, related codes and visible wiring or hose damage. Follow the vehicle's diagnostic procedure and test results before replacing parts.
Can I keep driving?
A code alone cannot establish whether driving is safe. A flashing malfunction light, severe shaking, overheating, oil-pressure warning or loss of braking or steering needs prompt attention. Stop in a safe place and seek assistance when control or engine safety is affected. Follow the vehicle handbook.