I've had issues with faulty IBS (Intelligent Battery Sensor) and low battery in the past, both very bizarre.
IBS failure: RPMs would drop dramatically during cruising as if the car lost electrical. Codes would read faulty Water Pump and IBS in this condition. The faulty water pump code was triggered because it lost electrical power (electric pump). Dealer replaced IBS and all is resolved.
Low battery - the bastard issue to nail down: Subtle rpm dips at idle/cold. HVAC fan would go in and out in really cold or really hot conditions. Yes, HVAC fan. I replaced fan/resistor thinking they were busted, but that was not the problem. Resolved with a new battery, in my case, Interstate Megatron Plus. These issues were resolved by mistake as I normally swap out batteries every 5 years or so I dont get stuck out in the cold.
These cars are dam sensitive to electrical glitches.
Last edited by bluskye; 12-29-2012 at 12:55 PM.