Warning: DM does not advise connecting an immobilisation relay to a safety critical system such as the ignition or fuel pump. A starter motor cut is recommended.


DM devices can immobilise using their outputs. Immobilisation can be done on:

  1. No Driver ID present
  2. Immobilisation command sent from the server.

Conditions are OR'ed together, so all conditions must be "off" for the immobiliser to be turned off.

The most common configuration is:
  1. Driver ID system params set to immobilise on no Driver ID in OEM System Parameters.
  2. Digital Output set to function immobiliser in OEM System Parameters.
  3. Digital Output set to Active Low in OEM System Parameters. When Driver ID is scanned, the output goes on and the immobiliser is turned off.
  4. Normally open contacts on the relay connected to the starter motor control cables. Do not connect to the high current starter motor drive cables.

For a more advance discussion on the difference between Active High and Active Low, read on...


Immobilisation can be done as active high or active low:
  1. Active High: immobilise when the output is ON. 
  2. Active Low: immobilise when the output is OFF.

With a switched ground output, when the output is on, it provides a ground. This is often connected to the ground side of the relay coil. The other side of the coil is connected to 12/24V. It is then important to choose which relay position turns the immobiliser on:
  1. Immobilise when the relay is de-energised (normally closed contacts on relay). When the relay is de-energised (output is OFF), the vehicle cannot start. The relay is energised (output is ON) to allow the vehicle to start. This is the most common configuration as the relay coil will draw current when the engine is running.
  2. Immobilise when relay is energised (normally open contacts on relay). When the relay is energised (output is ON), the vehicle cannot start. The relay is de-energised (output is OFF) to allow the vehicle to start. This is a less common configuration as the relay coil will draw current when the engine is off and may flatten the vehicle battery.