The computer can go haywire if the battery voltage drops below it's requirement. At least that's what happened on my Mazda a few weeks ago when it's battery went. Lights on the dashboard were blinking, MPH and RPM needles bouncing off their limits (engine wasn't even started).
I was expecting the mothership to beam me up...
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'01 Boxster S, 51k miles
'05 Mazda 6 Grand Touring Wagon
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