SES with no DTC's set?
 

I just finished a repair to my EVAP canister vent control valve. I had code 1448 saying that the valve was stuck open, so I looked at it and sure enough the piston was shot and it wasn't closing. So I replaced the control valve last night and reset the SES (through OBDII port). After about 200 miles the SES came on again. I hooked up the reader to see if something else was busted, but there are no codes set. The reader thinks the SES is off. So I reset it again. I'll have to see if this happens again, but has anyone ever seen an SES come up with no DTC's (either set or pending)? I have to get an inspection in the next two weeks so I need to get anything emissions related fixed, including the annoying SES. For an OBDII reader I use the Auto Enginuity connector and a laptop if that helps, and the car is an 03. Any ideas??? Thanks.

After resetting it again it came back on after a day. Still no DTCs show up. Also, the gas pedal method of resetting the ECU doesn't work anymore (at least when it's in this state). I have to use the OBDII interface. Does anybody know how to get into the Nissan specific information to figure out why this thing is upset??

Disconnect the battery, leave it off for 24 hours. re-connect and perform the ECU reset and idle air volume learning procedures (use Google to search this forum for the procedures.) It's possible your plain-jane code scanner didn't properly clear the stored code registers.

Thanks, I'll give that a try.