Advanced Diagnostics

Advanced Diagnostics - DTC P0400: Exhaust Gas Recirculation (EGR) System Leak Detected






General Description
The exhaust gas recirculation (EGR) deterioration failure conditions include a sticking lift sensor, restricted passages, and leakage from the external piping. At any specific EGR lift value there is a corresponding air/fuel ratio compensation value. If the air/fuel ratio compensation value is greater than the corresponding EGR lift value, the powertrain control module (PCM) detects a malfunction and stores a DTC.

Monitor Execution, Sequence, Duration, DTC Type, OBD Status






Enable Conditions






Malfunction Threshold
The air/fuel ratio (A/F) sensor response parameter according to the opening and closing of the EGR is 14,746 (LT80A) or less.

Driving Pattern






1. Start the engine. Hold the engine speed at 3,000 rpm without load (in P or N) until the radiator fan comes on.
2. Drive the vehicle at a steady speed of 25 mph (40 km/h) or less, for at least 5 minutes.
3. Drive immediately at a steady speed 26 mph (41 km/h) or more and engine speed between 1,500 - 3,000 rpm for at least 10 seconds.

- Drive the vehicle in this manner only if the traffic regulations and ambient conditions allow.

Diagnosis Details

Conditions for setting the DTC
When a malfunction is detected during the first drive cycle, a Pending DTC is stored in the PCM memory. If the malfunction returns in the next (second) drive cycle, the MIL comes on and a Confirmed DTC and the freeze data are stored.

Conditions for clearing the DTC
The MIL is cleared if the malfunction does not return in three consecutive trips in which the diagnostic runs. The MIL, the Pending DTC, the Confirmed DTC, and the freeze data can be cleared with the scan tool Clear command or by disconnecting the battery.