How do you test an EGR valve on a 2004 Mazda B2300?

To test the EGR valve on a 2004 Mazda B2300, first visually inspect it for any obvious damage or carbon buildup. Then, with the engine running, apply vacuum to the EGR valve using a hand-held vacuum pump; the engine should idle rough or stall if the valve is functioning properly. Additionally, you can check for proper operation by observing the EGR position with an OBD-II scanner while the engine is at operating temperature and under load. If the valve does not respond correctly, it may need cleaning or replacement.