What causes a SPN 520977 code?

SPN 520977 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 520977 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 520977 active.

How do I fix SPN 520977?

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 520977

Clutch Actuator Pressure Sensor

What it means

This code indicates an issue with the clutch actuator pressure sensor, reporting an out-of-range or erratic signal. This sensor is vital for proper clutch control in automated manual transmissions.