BMW X5: System Functions

The following system functions are described:

• Power management
• Electronic immobilizer
• Comfort start
• Air supply: 2-stage differentiated air intake system "DISA"
• Charge monitoring
• "Valvetronic" variable valve gear
• "VANOS" variable camshaft control
• Fuel supply system
• Fuel injection
• Ignition-circuit monitoring
• Alternator actuation
• Oil supply
• Engine cooling
• Knock control
• Tank ventilation
• Lambda control system
• Torque monitoring
• Evaluation of road speed signal
• A/C compressor actuation
• Intelligent alternator regulation
• Active air flap control

Power management

The integrated supply module provides the power supply to the DME control unit.

3 relays in the integrated supply module distribute terminal 87 (power supply) to the various components.

For memory functions, the DME control unit also requires an uninterrupted power supply via terminal 30.

Terminal 30 also supplies power to the integrated supply module.

The earth connection for the DME control unit is provided by several pins which are connected inside the control unit.

Power management includes the following functions:

• Closed-circuit current monitoring
• Consumer shutdown
• Control of the alternator
• Battery voltage monitoring

The battery voltage is regularly monitored by the DME control unit. If the battery voltage falls below approx. 6 volts or exceeds 24 volts, a fault is registered.

Diagnosis become active 3 minutes after the engine has started. This ensures that the effects of the starting operation or starting assistance on the battery voltage will not be registered as a fault.

> E60, E61, E63, E64

The intelligent battery sensor (IBS) monitors the battery. The intelligent battery sensor is connected to the bit serial data interface (BSD).

> E70

The fuse box supplies power to the DME control unit via the front power distributor in the junction box (for terminal 30 and terminal 87).

The intelligent battery sensor (IBS) monitors the battery.

Electronic immobilizer

The electronic immobilizer is an anti-theft and start-enabling device.

The CAS control unit controls the electronic immobilizer.

Each remote control unit has a transponder chip. The ignition lock is surrounded by a ring antenna.

Power is supplied from the CAS control unit to the transponder chip via this coil (remote control key does not require a battery).

The power supply and data transfer function is performed according to the transformer principle. For this, the remote control sends identification data to the CAS control unit.

If the identification data are correct, the CAS control unit activates the starter via a relay which is located in the control unit.

At the same time, the CAS control unit sends the DME control unit an encoded release signal (alternating code) to start the engine. The DME control unit only enables the start if a correct release signal has been received from the CAS control unit.

These operations may result in a slight delay in starting (up to half a second).

The following faults are stored in the DME control unit:

• Missing or disturbed release signal from the EWS control unit
• Alternating code from the CAS control unit does not tally with the alternating code computed by the DME control unit.

If a fault is detected, the engine start is blocked.

READ NEXT: