What causes a P1400 code?

P1400 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 P1400 code?

Drivability depends on the severity. Check the severity rating and verified driver reports on this page before continuing to drive with P1400 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

P1400

EGR high rate fault when estimated EGR rate > APV

What it means

The engine control module (ECM) detects that the actual Exhaust Gas Recirculation (EGR) flow rate is significantly higher than the commanded or expected rate based on engine load and operating conditions.