What causes a P1055 code?

P1055 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 P1055 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with P1055 active.

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

OBD-II

P1055

SFS Retarder Plausibility fault

What it means

P1055 indicates that the Smart Function Sensor (SFS) or VECU has detected a mismatch between the commanded Retarder (Engine Brake) state and the actual physical response or feedback voltage.