What does SPN 4339 mean?

SPN 4339 is a J1939 SPN fault code (SPN 4339 — Aftertreatment 1 DEF Line Heater 2) reported by the vehicle's diagnostic system.

What causes a SPN 4339 code?

SPN 4339 can be triggered by several issues — see the verified probable causes and step-by-step diagnostics shared by mechanics and owners on OBDIY.

Can I drive with a SPN 4339 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 4339 active.

How do I fix SPN 4339?

Follow the step-by-step diagnostic on this page, then read the verified fixes contributed by other Heavy Truck owners — the answer marked "Verified Cause" worked for the original poster.

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J1939 SPN

SPN 4339

SPN 4339 — Aftertreatment 1 DEF Line Heater 2

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