OK here's some update, I went under the van to find the O2 sensor is melted down so I'll be replacing it this afternoon right now I'm on my way to buy a new one that will definitely take care of the first two DTC's. About the EGR P0401 I checked the EGR tube and it is OK, it doesn't looks like they disconnected it because it is all rusted, so I took look at the EGR valve vacuum line and trace to the back of the engine to find out if wasn't properly fitted, it has a double boot connector, one of these boots was properly fitted, the other wasn't, I guess that will take care of the P0401 DTC.