Just bought a 2007 Automatic Xterra SE March 27th. Before buying, it had a CE light on for a cylinder 1 misfire so the guy took it to some mechanic and they only changed one coil and spark plug. Test drove it after and it was fine, bought it and couldnt even get it home without the SES light coming on. Got it coded and the code was P0420 for the low efficiency of the Cat. Took it back the mechanic guy and he supposedly changed the one coil on cylinder 1 and the light turned off. started driving it home and the light came back on. The only things I know to change is to replace all spark plugs and coils and then we want to change the radiator to kill the issue of it leaking coolant into the trans. The only other things wrong with the car is the driver window regulator is going out, the window goes down and you have to bang on the door to make it come back up. The other thing is the locking mechanism for the gas door, is messed up so we have a new clip to install to make it lock. Other than that im not sure what we need to do to get it running like it should again.