What causes a SPN 485 code?

SPN 485 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 485 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 485 active.

How do I fix SPN 485?

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 485

J1939 SPN 485 — Fuel/Air parameter

What it means

Engine Cooling Fan Supply - Voltage Below Normal, or Shorted to Low Source. This indicates the ECM detected an open circuit or low voltage on the fan clutch control line.