Q: How can you tell if your EGR valve is bad? on 2003 Chevrolet Silverado 1500

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My truck recently failed emissions testing. My truck has been knocking during acceleration and also the exhaust smell is really worse than ever. Can the EGR Valve be the culprit?
(1) Answer
A failed EGR valve should turn on the Service Engine Soon light. The best way to test the valve is with the proper scan tool. Not all scan tools will have the functions necessary to control the EGR valve but using a scan tool the does will enable you to open and close the valve and note the change in engine performance when the valve is open. I would suggest the first thing you should to is to see if any fault codes are stored in the PCM. With the truck running as you say it does is would think there are fault codes stored. You will need a code reader or scan tool to access the codes. You should check out and repair any codes stored before performing any other repairs.