What causes a SPN 4776 code?

SPN 4776 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 4776 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 4776 active.

How do I fix SPN 4776?

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 4776

Detroit DD13/DD15/DD16 SPN 4776

What it means

Inlet NOx Sensor Relative Humidity. This code indicates that the humidity signal from the Inlet NOx sensor is either out of range or not providing a valid signal to the ACM.