What causes a P0594 code?

P0594 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 P0594 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with P0594 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

OBD-II

P0594

P0594 Cruise Control Servo Control Circuit Open

What it means

Indicates that the Engine Control Module (ECM) has detected an open circuit in the cruise control vacuum or electronic servo command loop.