BMW 7 Owners & Service Manuals

BMW 7 Series: Replacement And Start-Up

Removing and installing the ICM control unit

The ICM control unit performs tasks that are important for many vehicle functions, e. g. provision of sensor signals. If the vehicle were operated without the ICM control unit installed, a large number of vehicle functions would not be available. In the area of dynamic driving systems, for example, the Servotronic and stabilization functions would no longer be available. In addition, fault code memory entries would inevitably also be generated in many control units.

NOTE: If the ICM control unit needs to be replaced, the repair instructions must be observed without fail.

For example, the vehicle battery must be disconnected before removing the control unit and reconnected following the installation. This is the only way to ensure synchronized restarting of the control unit assembly.

NOTE: Once the new ICM control unit has been installed, it must be started up with the assistance of the diagnostic system. To do this, the following steps must be carried out (depending on the equipment specification):

  • Calibration of the sensors integrated into the ICM
  • Calibration of the ride-height sensors
  • Initialization of the Integral Active Steering.

Calibration of the sensors integrated into the ICM

The signals from the acceleration and yaw rate sensors integrated into the ICM are referenced to their housing.

However, in order to be useful to the dynamic driving systems, these variables must be referenced to the vehicle coordinate system. In order for the ICM control unit to be able to carry out the necessary conversion, it requires corresponding correction values. These are determined during the one-off calibration procedure and stored in the ICM control unit.

NOTE: The instructions of the diagnostic system must be followed precisely during calibration of the sensors integrated into the ICM. It is particularly important for the vehicle to be standing on a surface that is level in both the longitudinal and lateral directions. If this is not the case, incorrect correction values will be determined that may cause the dynamic driving system to malfunction.

Calibration of the ride-height sensors

The measurement signals from the ride-height sensors are evaluated by means of voltage measurement in the ICM control unit. The ICM control unit cannot calculate the actual ride-level heights in millimeters on the basis of this information alone. To perform this calculation, the ICM control unit must be able to map the voltage signals it receives to reference values. This is the only way to establish a relationship between the measurement signals and the actual ride-level heights at the wheels. These reference values are determined during a synchronization procedure.

NOTE: The ride-height signals in the ICM must be synchronized in the following cases

  • following replacement of the ICM control unit,
  • following replacement of a ride-height sensor or
  • if prompted to do so by the test schedule of the diagnostic system (due to a fault code memory entry in the ICM).

The synchronization does not have to be carried out if a wheel has been changed.

NOTE: The following points must be observed in order to perform the synchronization using the diagnostic system

  • the air suspension control operations must be blocked (remove fuse for EHC control unit)
  • the ride-level heights must be measured using a tape measure and
  • the rim size must be determined.

The diagnostic system also refers to the ride-level height reference values (design position). These values are used by the diagnostic system and ICM to calculate the reference values for the conversion that are ultimately saved in the ICM control unit.

The ride-height signals in the EHC control unit (if installed) and the ride-height signals in the ICM control unit must be synchronized together.

Initialization of the Integral Active Steering

The ICM control unit calculates the higher-level control functions for the Integral Active Steering. The output signals of this control function are the reference steering angles, that should be set at the front and rear axle.

This is performed by the AS and HSR actuator control units together with the actuators. The actual angle set at the front and rear axle is sent to the ICM control unit as acknowledgment. The control circuit of the driving dynamics control system closes once this information has been received.

To determine this information correctly, the Integral Active Steering must be initialized. During this initialization procedure, the center of the steering gear at the front axle is determined and the corresponding signal values are stored (for example).

NOTE: The Integral Active Steering must be initialized under the following circumstances:

  • the ICM, AS or steering column switch cluster control unit has been replaced or
  • the steering angle sensor in the steering column switch cluster has been calibrated or
  • the steering gear has been replaced or
  • if requested by the diagnostic system due to a fault code memory entry in the test schedule.

During the calibration the diagnostic system issues several prompts to steer from one limit position to the other.

The internal combustion engine should be running and the vehicle should be standing on the ground of the workshop when calibration is in progress. These marginal conditions most closely resemble the conditions under which the customer operates the vehicle and deliver the best initialization results. If the front wheels are resting on revolving and sliding supports, or are suspended in mid air if the vehicle is raised, this may lead to unsatisfactory results.

Calibration of the steering angle sensor in the steering column switch cluster

In addition to the signals from the motor-position sensors of the Integral Active Steering, the ICM control unit also imports the signal from the steering angle sensor in the steering column switch cluster. This is used by the ICM to determine the effective steering angle ("see FUNCTIONS" section).

This is why it is important that the ICM receives a correctly mapped value from the steering angle sensor.

NOTE: The steering angle sensor must be calibrated if the steering column switch cluster is replaced or reprogrammed. A calibration must also be performed if this is requested in the test schedule of the diagnostic system as the result of a fault code memory entry.

The steering angle sensor must be calibrated before the ICM can calculate a correct effective steering angle and make this available via the bus system.

NOTE: Once the steering angle sensor has been calibrated, the instructions of the diagnostic system must be precisely followed.

The vehicle must be standing on even ground during calibration. The steering wheel must be in the straight-ahead position (visually).

Start-up, short range radar sensors

If the option "Active speed control with stop&go function" is installed in the vehicle, this will include the necessary radar sensors.

Although short range radar sensors are intelligent sensors that perform the functions of a control unit they cannot be accessed directly via the diagnostic system. The ICM control unit acts as a "go-between" between the short range radar sensors and the diagnostic system which is why the ICM also controls the start-up process for the short range radar sensors.

NOTE: The short range radar sensors for ACC Stop&Go must be started up if one (or both) short range radar sensor(s) is/are replaced. In this instance, the diagnostic system communicates with the ICM control unit. The ICM in turn controls the corresponding functions in the short range radar sensors.

The installation position and, most importantly, the angle at which they are installed relative to the vehicle's longitudinal axis, are entered in the newly installed short range radar sensors during start-up. A measurement does not need to be carried out in this case. The angle entered is the angle predetermined by the construction and the form of the bumper support.

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