What causes a SPN 3520 code?

SPN 3520 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 3520 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 3520 active.

How do I fix SPN 3520?

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 3520

J1939 SPN 3520 — Body/Chassis parameter

What it means

The SPN 3520 is a generic J1939 parameter indicating a fault within a Body/Chassis component, often related to auxiliary equipment communication or sensor data reported to the vehicle network.