Service bulletin SI B12 15 12 posted to Bummerfile.com lets dealers reprogram the system to default to the "last user mode," meaning that the system will either be on or off when the key is cycled based on the driver's last settings. A button located near where a key slot would traditionally be has always allowed for manual control of the auto start/stop system, but BMW previously programmed the system to default back to on with every key cycle.
Like other automakers that use auto start/stop systems, BMW's is aimed at curbing idling emissions. Although the EPA's current fuel economy standards don't take into account much idling time, future revisions of the federal test are likely to be more realistic. As many as 8 million cars in the U.S. are expected to have auto start/stop systems by 2017.
