Advance Auto Parts reported a code "P0456" then wrote 4 lines on a scratch paper:

P0456
Leak Detection
Pump very small
Leak

I didn't see the screen... just the note.

Questions:

Q1) How accurate are these devices in a clerk's hands? (1 = not at all; 5 = very accurate)

Q2) Does "Pump" REALLY mean the device has isolated the small leak to be emanating from the pump itself or is this "painting the diagnosis with a broad brush" so to speak and the leak could be anywhere from the canister to the engine or wherever?

 

Accurate enough, actually you could read that code (and others) with the "key dance"
Could be as simple as a loose or bad gas cap seal.
What year? 99-01 LDP system
02and up NVLD
Many discussions here: www.300mclub.org