Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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: see 61 21 1AZ in 61 21 BATTERY WITH TERMINAL .
- Connect and switch on battery charger
- Switch ignition on
NO RELATED
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.