1992 Grand Prix LE 3.1

I have a 92 Grand Prix 3.1. I have had a tune up done, air filter,fuel filter ,feul injector,PCV valve,oil changed,transmission fluid changed with new filter, map & O2 sensors replaced and a new power steering line. I went to take my emissions and I need an ERG valve and my catilyic converter checked. my question is what is a ERG valve, will my engine light blink on and off because of it and why dose my low coolant light come on when the radiator and the resevoir are full ?

The egr valve is an emissions device that controls certain emissions by recirculating gases in to the combustion chambers. If it is bad it may cause a code in the computer and cause the light to come on but it may not. If the EGR is not working then you will see high emissions on a test. I responded to your other thread telling you how to change it. As for the convertor, you may have a bad one that is not effectively converting the CO to CO2. Sometimes they will plug up especially as they get older. If you need a new one it will cost from $3-5 hundred to replace. Don't go to a dealer have an exhaust place check it for you, will be cheaper. As for the low coolant light the sensor could be bad or you may have a little air in the system. As long as you are sure the coolant level is good and the car is staying cool don't worry about it. If it is a total annoyance then replace the sensor. Hope this helps.