If it has the grey SKIM key, the module can store a code if it sees a problem like a wrong key or no SKIM messages to the PCM, etc, but only the dealer can retrieve them. It might point in the general direction of the problem.
96 GC Limited V8 245,000 miles Scrapped
04 GC Limited 4.0 264,000 miles
96 GC 4.0 175,000