What causes a SPN 5621 code?

SPN 5621 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 5621 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 5621 active.

How do I fix SPN 5621?

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 5621

Cummins fault code 5621

What it means

Intake Manifold 1 Pressure - Data Erratic, Intermittent, or Incorrect. The ECM detects that the intake manifold pressure signal is not characteristic of normal operating conditions.