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.
Car Access System: Introduction
The Car Access System (CAS) controls access to the vehicle.
The CAS control unit is the master control unit, e.g. for the following systems:
- Electronic immobilizer
- Central locking system
- Comfort Access
- Electronic steering lock
- Power windows
The CAS is constructed differently in the various model series.
- E60, E61, E63, E64 until 09/2005:
The CAS and the ignition starter switch are 2 separate components.
- E60, E61, E63, E64 from 09/2005:
Ignition starter switch and conventional ignition key discontinued. The slot for the remote control and the START/STOP button are new features.
- E70, E81, E87, E90, E91, E92, E93 from start of series production:
Slot and START/STOP button
Use the Manual With the Right Hardware
Pair factory procedures with proven DIY tools so the instructions are easier to execute.
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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.
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