why would be abs, brake, esp, traction control lights come on in my 2009 Routan

Hello, when did the problem start occurring? The warning light, I would guess, is coming from an out of range sensor reading of some kind. This can be due to multiple possible causes. A diagnostic tool can monitor speed sensor information when the problem occurs to see which area to focus in on. When you say that your dealer couldn't get a clear reading, it leads me to think that this concern happens only intermittently perhaps and will take some extended time to try and duplicate during testing.