Hey Tom, welcome to the forums!
For our information, is the EVAP monitor the only one that hasn't completed, or are there other monitors still incomplete? I ask because some vehicles are very picky about the order in which they run monitors. A borderline O2, for example, can stop the whole process.
I was going to ask about fuel level, as the EVAP monitor will usually only run between 3/4 and 1/4 fuel levels, but then you said you drove it 500 miles... I'm sure you filled up somewhere in there!
I understand that you don't have a fancy scanner, but do you have access to scan data? Good ol' Global OBD data will work. Mostly I'm interested in checking the ECT and IAT PIDs to make sure they more or less agree. After sitting overnight, both sensors should read within a few degrees of one another.
There's a fantastic PDF on GM monitor enable conditions that you can reference if you're looking at scan data:
service.gm.com/gmspo/mode6/pdf/2002/2002file4.pdf
Down on page 34 is the criteria for P0440. How hot has it been in your area recently? One of the enable conditions is an ambient temperature of less that 86 degrees, or 30 degrees celsius. If it never goes below that, then the test will never run.
