Technical Description of OBD-II Trouble Code
Malfunction in the Flow of Exhaust Gas Recirculation (EGR)
What does that signify?
This diagnostic trouble code (DTC) is a generic powertrain code, which means it is applicable to vehicles equipped with OBD-II. Although it is a generic code, the specific repair steps may vary depending on the make and model of the vehicle.
The exhaust gas recirculation (EGR) valve is a vacuum-controlled valve that regulates the amount of exhaust gases that re-enter the cylinders.
The powertrain control module (PCM) determines the amount based on engine load, temperature, and other conditions. If the PCM detects that the amount of exhaust gases entering the cylinder is insufficient or non-existent, this code is set.
Symptoms
The driver is unlikely to notice any symptoms other than the malfunction indicator lamp (MIL) illuminating. However, non-visible symptoms include increased combustion temperature and increased Nox emissions.
Causes
A code P0400 may indicate that one or more of the following has occurred:
Possible Solutions
Since EGR valve designs vary, no single test will be sufficient:
Related EGR codes: P0401, P0402, P0403, P0404, P0405, P0406, P0407, P0408, P0409
