Guess I'll have to sell it., EGR Options

[ST204GT83]

Today is my last day of legal driving. We found the new vsv I bought was faulty, so I bought another one, we tested it, it works. Check engine light came back on last night, still egr. Replaced all the necessary parts, egr, modulator and vsv, new vacuum lines, everything is clean. We are truly at a loss. Maybe 02 sensor? I read about it. P0401. Never ending. This sucks.

[slavie]

Have you actually tested the EGR system? The factory service manual provides very, very detailed steps on how to test every component of the system. Throwing parts at the problem, while easy, is not the best solution, as new parts can be defective as well, especially if you're getting aftermarket stuff.

To set the P0401 or 0402 codes, the computer actually goes by the MAP sensor data. Basically, when EGR is opened or closed, the computer is programmed to look for a specific change in the engine vacuum, all else being equal. If there is no change in the vaccum reading, you'll get P0401 (malfunctioning EGR VSV, modulator, or valve); alternatively, if the change in vacuum is too great, you get P0402. There is literally no other way for the computer to determine whether the EGR system is working (I'm not sure if the ECU measures the draw on the VSV pin, so that could be another code setting criteria).

If you actually hook up a vacuum gauge to the system and follow the diagnostic steps, you should be able to see exactly the condition that set the code. Also, look at the freeze frame data.

I too fail to see how EVAP system component - the canister - will solve your EGR system code. Theoretically if there was a break in the EVAP system that was leaking too much vacuum you might see an impact on the EGR system, but then you would be seeing EVAP system codes as that has the vapor pressure sensor and is a much easier system for the ECU to monitor and throw codes for.