What causes a SPN 520951 code?

SPN 520951 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 520951 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 520951 active.

How do I fix SPN 520951?

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 520951

Brake Lining Wear Sensor, Auxiliary Axle Left

What it means

This code indicates excessive wear on the brake pads for the left side of an auxiliary axle, signaling replacement is due. The likely root cause is normal wear over time.