61 20 908 Performing battery "power reset" (for programming/coding control unit(s))

The following steps must be carried out for a "power reset": 

• Switch off and disconnect battery charger
• Switch off ignition

  Cars with ignition key:  Turn ignition key to 0 position

  Cars with identification sensor:  Remove identification sensor from slot

  Cars with comfort access system:  Make sure terminal is in 0 position

• Disconnect battery negative terminal
• Reconnect battery negative terminal (to ensure bus activity)
• Waiting time (5-10 seconds)
• Disconnect battery negative terminal
• Waiting time (1 minute)
• Connect battery negative terminal and tighten, tightening torque 61 21 1AZ
• Connect and switch on battery charger
• Switch ignition on