Mercedes-Benz C-Class (W205) 2015 - 2021 Owners Manual: Anti-theft protection

Function of the immobilizer

The immobilizer prevents your vehicle from being started without the correct SmartKey.

The immobilizer is automatically activated when the ignition is switched off and deactivated when the ignition is switched on.

When leaving the vehicle, always take the Smart‐ Key with you and lock the vehicle. Anyone can start the engine if a valid SmartKey has been left inside the vehicle.

In the event the engine cannot be started (yet the vehicle's starter battery is charged), the system is not operational. Contact an authorized Mercedes-Benz Center or call 1-800-FOR-MERCedes (in the USA) or 1-800-387-0100 (in Canada).

ATA (anti-theft alarm system)

Function of the ATA system

If the ATA system is armed, a visual and audible alarm is triggered in the following situations:

• when a door is opened
• when the trunk lid is opened
• when the hood is opened

The ATA system is armed automatically after approximately ten seconds in the following situations:

• after locking the vehicle with the SmartKey
• after locking the vehicle using KEYLESS-GO

Indicator lamp 1 flashes when the ATA system is armed.

The ATA system is deactivated automatically in the following situations:

• after unlocking the vehicle with the SmartKey
• after pressing the start/stop button with the SmartKey in the stowage compartment
• after unlocking the vehicle using KEYLESSGO

When the Mercedes‑Benz emergency call system is active and the alarm stays on for more than 30 seconds, a message is automatically sent to the Customer Assistance Center.

Deactivating the ATA

• Press the , or button on the SmartKey.

  or

• Press the start/stop button with the Smart‐ Key in the stowage compartment.

Deactivating the alarm using KEYLESS-GO:

• Grasp the outside door handle with the SmartKey outside the vehicle.