What causes a P0505 code?

P0505 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 P0505 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with P0505 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

P0505

P0505 - Idle Air Control System Malfunction

What it means

The Engine Control Module (ECM) has detected an unexpected RPM variance or electrical fault within the Idle Air Control circuit or engine speed governing system.