Tha controller can certainly fail, but I have never heard of one failing on the posts. Check the two vacumm lines, and see if they are not reversed on the controller. In my car, looking from the top, you can see two vacumm lines leaving the controller. The yellow one is in the upper port and a beige is on the lower one. From what I know, under certain conditions the ECU sends a signal to the controller and it opens letting vacumm activate the EGR (opens it)letting a portion of exhaust gas into the intake. Under idle it should be closed full time. If you get the 154 code that means exhaust gas in passing thru when it shouldn´t and that is picked up by the temperature sensor in the egr body. Besides the vacumm lines, check the connector on the controller and for good measure the connector on the egr temperature sensor. When you cleaned the egr, did you check if the internals were moving freely by applying vacumm to it? Are you sure there is not some piece of hardened gunk in there preventing it from closing?