What causes a SPN 3257 code?

SPN 3257 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 3257 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 3257 active.

How do I fix SPN 3257?

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 3257

DPF Intake Temperature Sensor High Circuit Voltage

What it means

The Engine Control Module (ECM) detects that the signal from the Diesel Particulate Filter (DPF) Intake Temperature sensor is higher than the maximum expected voltage, typically indicating an open circuit.