What causes a SPN 1874 code?

SPN 1874 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 1874 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 1874 active.

How do I fix SPN 1874?

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 1874

Aftertreatment SCR Catalyst Temperature Sensor 1 Bank 1 High Voltage

What it means

Indicates that the SCR inlet temperature sensor voltage is higher than the expected operating range, typically signifying an open circuit or internal sensor failure.