What causes a SPN 6776 code?

SPN 6776 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 6776 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 6776 active.

How do I fix SPN 6776?

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 6776

Cummins fault code 6776

What it means

Aftertreatment 1 Diesel Exhaust Fluid (DEF) Deposit Sensor - Logic Error. The ECM detects that the sensor signal is irrational or reporting excessive deposit buildup that does not match engine operating conditions.