I have a 2000 Mitsubishi Eclipse GT.I just replaced the EGR Valve yesterday, and disconnected the battery to reset the code.My old valve was nasty and loaded with carbon and the valve wasnt even opening.As soon as I drove it out of my driveway with the new valve I IMMEDIATELY noticed the difference, as it was back to normal and felt like the car moved quick again without the knocking. But after about 20 miles, the light came back on [the car is still running perfect].Today I went to Autozone and had it scanned, and sure enough, code P0403 came up as EGR Valve Circuit. He cleared the code out, and I drove to a nearby store, and when I came back out and turned my car on, the code was back AGAIN.What's the problem?If you have an idea of something else that I should check, please give me an idea of where it is located.Thank you.
Your old valve was probably stuck open for whatever reason. If it were stuck closed you would feel no difference whatsoever in driving. The EGR doesn't do anything at all for performance. In fact, all it does is recycle unburnable gasses back into the intake, which causes carbon deposits and very well lowers performance (ableit only a little, and it only opens during acceleration and cruising so you don't notice it). That being said, the first thing you should check is your command circuit. Is there a vacuum line coming to the valve to open it by vacuum, or are there wires going to it? If it is a vacuum line, then check it very carefully for breaks. If it is electrically controlled, a remote-mount solenoid may be the problem, or if it is integral, I would start looking at the sensor (there are a few different types of EGR position sensors, and they may all be the culprit). This code most likely comes from the sensor detecting that the valve is not opening. Keep in mind this will be the valve, something that controls the valve, or the sensor that monitors the valve.
if your valve was carboned up then you Dp sensor is probably clogged as well and that would cause the light to come on and it would give that code. You can more than likely take it off and clean it really well with something like LPS or brake cleaner...carb cleaner would work also
Check all your vacuum hoses for cracking or leaks
