What causes a SPN 66 code?

SPN 66 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 66 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with SPN 66 active.

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 66

J1939 SPN 66 — Engine parameter

What it means

This code refers to an "Engine Parameter" error, specifically mapped to the Intake Manifold Pressure (Turbo Boost). It indicates the value recorded by the sensor is out of range or inconsistent with engine speed/load.