Ok, after two days (5-7 trips) the CEL comes on posting code P2402 as usual. Open the gas cap provides a woosh of gas odor suggesting that there really is gas pressure in there. Other suggestions from the Auto Zone printout include electrical conductivity, bad sensor or bad pump. Seems all of these would fail every time not just once in awhile, and loss of gas pressure would certainly happen every time. Mazda 6 2006 about 53,000miles.
I find this interesting. So here is my 2cents at de-mystifying this part
of the mazda5.
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In the case of '2402' EVAP system leak detection pump motor circuit high.
There are 3 suspect parts, electrical shorts (corroded terminals causing high current to ground),
Bad airpump motor assy.
Defective PCM.
From the above, the System turns on pump and obtains initial load current.
Then change over valve opens. load current drops and slowly climbs up.
The rate of the load current increase will tell the computer if there
is 'slow leak' or gross leak.
From the readings, the system can also know if the change over valve
has failed.
BTW, the system also knows if the air filter (there is a small air filter in the evap detection system) is clogged.
And then the system assigns them individual error codes. amazing!
But then to do the above accurately, it has to make sure that the
pump motor is also working perfectly.
In your case, the system has detected that the load current is
read to be 'too high'. If left unresolved, it may not give accurate
'leak detection functions'. So it gives you the 2402 error, that
you may replace the pump, or check the circuit for shorts, etc.
These are just my interpretation.
Conscious with repair time, I figure the tech will just put in a new
air pump. And observe.