What causes a P2439 code?

P2439 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 P2439 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with P2439 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

P2439

Secondary Air Injection System Air Flow/Pressure Sensor Circuit Intermittent

What it means

The Engine Control Module (ECM) detects an erratic or intermittent signal from the Secondary Air Injection (SAI) pressure sensor, used to monitor air flow during cold start emissions reductions.