1995 Century Check Engine Soon light

[MichiganDave]

On my 1995 Century, my CHECK ENGINE SOON light keeps going on. When I took it to the mechanic, he hooked up the car and said that the CHECK ENGINE SOON light was on because of the EGR valve. I replaced the EGR valve and now the CHECK ENGINE SOON is still going on. When I took it back to the machanic, he said that when they hook it up to determine why the light is going on, it says it is the EGR valve again. Obviously my EGR valve is not faulty. What would trigger my CHECK ENGINE SOON light to keep going on? The mechanic checked the EGR valve and said there is nothing wrong with it. What is the problem here?
The next time I purchase another car, it won't be a GM (General Maintainance). Any input would be appreciated.

[roaddirt]

My understanding is that even with good EGR valve you can get a code due to problem in EGR System like passages plugged due to carbon deposits, vacuum leak at gaskets or metal hose etc.
Did you use new gasket. Did you check the passage underneath of EGR valve for black deposits. You might need to remove, I think, upper intake manifold and clean it's passaages.

Just thoughts, do research before you make step.

Roaddirt

[IQtippa]

I had the same problem with the light and got it fixed on monday. In my case, it was the oxygen sensor. the light has stayed off ever since

[bignoisey]

I had the same problem with my 95 Chevy truck. As I remember the EGR fault is determined indirectly by the oxygen sensor monitoring the exhaust stream afrter the computer tells the EGR to open. Maybe the Oxygen sensor is faulty. I never fixed that problem since it only happened very infrequently before I sold it.