"EGR stands for Exhaust Gas Recirculation. It is part of the vehicle emmissions system, and is used to reduce combustion temperature and pressure to control Oxides of Nitrogen. There are generally three parts to the EGR system: the EGR valve, an actuator solenoid, and a differential pressure sensor (DPF). These things work together to deliver the correct amount of recirculation based on engine temperature, load, etc. The P0402 code means that OBD detected an excessive amount of EGR.
SymptomsYou may notice drivability problems such as the engine may surge off idle. There may also be other symptoms.
CausesA code P0402 most likely means one or more of the following has happened:
The DPFE (differential pressure) sensor is faulty and needs to be replaced
There is a blockage in the EGR (most likely carbon buildup)
The EGR valve is faulty
The EGR valve may not be opening due to a lack of vaccuum
Possible Solutions With a P0402, it is common for people to replace the EGR valve, only to have the problem return. The most likely solution is to replace the DPFE sensor.
Check the voltage at the DPFE sensor both at idle and when the EGR is open
Replace the DPFE sensor"
The above is a more technical answer. The shorter story is that ehaust fumes are sucked into the engine to lower pollution. The passage from the exhaust to the engine intake is important also. Some time on higher mileage vehicles soot from the exhaust builds up and will not let the valve close. It is only supposed to be open when the engine is running fast.
The least expensive repair might be to simply clean EGR the port and valve with carb cleaner and an old toothbrush.
Ford has had problems with their DPF sensors. These let the computer know what is going on with EGR flow. The will fail and give false information. The computer then does things it shouldn't. This would be the next thing I would test and/or repair/replace.
Good luck and let us know. :)
Wednesday, March 15th, 2006 AT 8:36 AM