The main problem with the EGR valve is that it sticks open. After the engine has fired and the exhaust is pushed out the exhaust manifold, it is channeled up to the turbocharger. On the way there, there is a bypass that takes a small amount of exhaust and redirects it into the EGR cooler. After the cooler lowers the exhaust gas temperature, it is then channeled to the EGR valve. After time, the soot buildup on the valve makes it stick and eventually it will stop working (it will usually be stuck open). The problem that most people have is that the fuel mileage goes down, the vehicle runs poorly and the check engine light comes on.
Another problem with the soot from the exhaust is that it tends to plug the exhaust back pressure sensor and tube. This will cause P0470 and P0471 codes and the vehicle will run very rough.
- P0470: EP Exhaust pressure sensor faulty sensor: open signal return, faulty PCM.
- P0471: EP Exhaust pressure sensor range/performance faulty sensor: restricted supply tube, faulty PCM.