What causes a SPN 520328 code?

SPN 520328 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 520328 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 520328 active.

How do I fix SPN 520328?

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 520328

DEF system has been over pressurized

What it means

The DEF (Diesel Exhaust Fluid) Pump has detected that the system pressure has exceeded the maximum allowable threshold, typically above 12 bar (174 psi).