What causes a SPN 671 code?

SPN 671 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 671 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 671 active.

How do I fix SPN 671?

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 671

J1939 SPN 671 — Engine Management parameter

What it means

Engine Speed Sensor Signal Error. The Engine Control Module (ECM) is receiving an erratic, missing, or out-of-range signal from the crankshaft speed sensor.