Affected Vehicle:
2006 BMW 550i Base 4.8L, V8, MFI, DOHC

Customer Concern:
Vehicle has an intermittent no-start problem and the battery has gone dead.

Potential Causes:
Incorrect battery or the ­comfort access module.

Battery Tests:
1. This vehicle uses a glass mat type battery and requires reprogramming if a conventional lead-acid battery is used as a replacement.

2. Glass mat batteries can be damaged if charging voltage goes above 14.8 volts. Quick charge strategies are not recommended as they will damage the glass mat battery.

3. Battery replacement needs to be registered in the power module regardless of battery type. After eight battery replacement procedures, the power module will require replacement as well.

4. Using a scan tool to interrogate the power module and comfort access module will often help explain battery/starting problems.

Confirmed Fix:
Initialized Battery: After battery replacement, the energy management system needs to be notified of a new battery. Initialize the battery to the vehicle with a BMW-­compatible scan tool.

Tech Tips:
The comfort access module performs the functions of the ignition switch. It controls all ignition switch functions and is diagnosable with a BMW-compatible scan tool.

Courtesy of Identifix’s “Five Fast Fixes”