The ODO is stored in the PCM. The PCM is not dealer-reprogramable as far as the ODO is concerned - they have to be sent off to a Factory Authorized place and they have to be authorized by GM.
As for the Trip A and B discrepancy, that is actually known. For some reason, bogus numbers get input into that area as it is not protected like the factory ODO. There are bulletins out for service techs and one of the things is to reset both trip a and b during the Pre-Delivery Inspection. Your's just got missed.
So FYI, dealerships can NOT reset ODOs.
Additionally, keep in mind that during the Pre-Delivery inspection, dealerships are *basically* required to drive the vehicle approx. 10 miles during the inspection (we don't usually but that does happen). Plus vehicles have about 10-15 miles on them from the factory depending on how many times they were ramp-loaded and unloaded.
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