Ed,

Odd electrical trivia.   Older eeproms were rated at 3.3V, so below 2.7V they ignored any read or write information.

We had a uC that would start "jabbering" on the data and clock lines when power was caming up.   Since reset occurred once power was good, it was never an issue.   Problem is the eeprom manufactures started shipping parts that were functional from 1.8V to 3.3V.  So once power was at 1.7V, it accepted writes, corrupting the eeprom. Just to drive the engineers crazy only some lots and some devices 'jibbered' away.   Yes, amazing I still have any hair left. :)

That is pretty rare, but has happened.

Yes, Mike -- Interesting you're only seeing an issue with the "B" controller. Still triple check the power, grounds, and rest of the connections.  
 
> Since the fuel map is stored in non-volute memory, it’s hard to figure out how it is being re-written or destroyed.  Normally (as you know) access to EEPROM on a chip is a rather non-trivial process.   Since the A and B controller are two different chips, I suppose there could be a problem with the B chip – but, while that does happen, it’s pretty rare.  Have not had one myself (yet).