While monitoring the Exhaust Gas Recirculation (EGR) valve pintle position the Powertrain Control Module (PCM) detected the closed position sensor voltage higher than the learned closed position voltage.
Engine Light ON (or Service Engine Soon Warning Light)
P1404 Chevrolet Description
The Powertrain Control Module (PCM) determines that the EGR valve is stuck open if the actual Exhaust Gas Recirculation (EGR) position and the learned closed EGR position vary by more than a predetermined value. The PCM tests for a stuck valve when the desired EGR position is at 0%. The PCM commands the EGR valve to 100% during certain driving conditions in order to clear a possible restriction from the EGR valve if the PCM determines that the valve is stuck open. The PCM retests for a stuck valve when the desired EGR position returns to 0%. A failure timer increments if the stuck EGR valve condition is still present. This DTC sets when the timer reaches a predetermined value.