What causes a SPN 1821 code?

SPN 1821 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 1821 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 1821 active.

How do I fix SPN 1821?

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

Log in Sign up

J1939 SPN

SPN 1821

DPF Intake Temperature Sensor

What it means

The temperature sensor at the DPF inlet is providing an erratic or out-of-range signal.

Sign in to view symptoms, probable causes, diagnostic steps, severity, and related codes

Log in Sign up free