Generally "reflash" refers to a complete replacement of the PCM memory or a module ROM for some reason - electromagnetic interference or electrical spikes have contaminated some or all of the memory.
"Relearn" refers to a specific procedure to reset monitoring or parameters for a sensor or control - as in a CranKshaft Position sensor relearn (determines electronic timing offset between original and replacement CKP sensor(s)).
Depends on what you're looking for........BUT, relearns and reflashes are tied to the original car year and VIN. ("Hey, Joe, can you reflash my PCM to a Z rated STS program ???" Joe at the dealer: "No". "Hey Joe, when you install my new CKP's, will you do a relearn ???" Joe at the dealer: "Yes".)
the pcm is not the oem .the crank sensors have been replaced three times and now i guess i need a re-learn.does the dealer need the car or just the pcm.legally i cant drive the car because it failed state inspection for the check engine light.i'm between a rock and a hard place