What causes a SPN 3309 code?

SPN 3309 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 3309 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 3309 active.

How do I fix SPN 3309?

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.

OBDIY

J1939 SPN

SPN 3309

SPN 3309 FMI 14 - Cylinder #1 High Pressure Cylinder Pressure

What it means

Indicates that the engine control module has detected a high pressure or combustion anomaly in cylinder number one, typically related to cylinder pressure sensor feedback.