94 Explorer EGR valve

Check enging light came on the other day, so I attached my scantool and got the codes from my 94 Explorer (123k miles) the other day and it indicated that the EGR valve was bad. I just replaced the EGR last Oct. Could the new one have gone bad that soon? Is there something else that I should be looking at? The KOEO codes were 335 and 332. THe KOER codes came up 326, 538, 536.

Thanks.