Steering-Angle Adjustment
Steering-Angle AdjustmentAfter working on the steering, it is necessary to carry out a steering angle adjustment with the steering column switch cluster (SZL) control unit!
The Dynamic Drive system is dependent on the exact zero balance of the steering angle!
The maximum tolerance for a deviation is +/ 1°. Precise performance of a wheel alignment check and adjustment is essential!
Steering-angle adjustment must always be performed on the KDS and in accordance with the BMW specifications! Each time the Dynamic Drive or SZL control unit is flashed results in a loss of the zero position! A steering angle adjustment is necessary!
Dynamic Drive Commissioning
The commissioning procedure must always be carried out once the system has been opened or a part has been replaced. This also applies after the lateral acceleration sensor has been replaced.
The following conditions must be guaranteed for matching the lateral acceleration sensor and the two pressure sensor offset values:
^ The vehicle must be stand level on all four wheels
^ The vehicle must be unladen
^ The engine must be idling
^ Rest status (doors closed, persons are not allowed in the vehicle)
No persons may remain within the vicinity of moving chassis parts during the commissioning (both in the works and the workshop). In addition you must ensure that the basic commissioning conditions (temperature range, constant engine speed etc.) are maintained. The ground clearance must not be limited and the doors must be closed. The arms of the hoist may no longer be situated beneath the car.
The commissioning procedure is split into five stages which follow on from each other automatically:
Dynamic Drive Venting
A venting routine must be carried out using the diagnostic tester if the Dynamic Drive system was opened hydraulically.
The venting operation is performed exclusively by way of the commissioning routine of the diagnostic tester and not at the pressure relief valves or at the screw plugs of the oscillating motors!
If the test still detects air in the system, a short movement trip should be made if necessary.
The commissioning routine must then be repeated after the short trip.
In the event of an extreme leak or suspected subfunction of the pressure relief valves (noticeable by the rattling noises in the front end), the pressure relief valves and the pneumatic lines must be replaced with new components.
Diagnosis
The following faults can be detected at the components:
System Shutdown (Fail-safe Status)
Depending on the fault, the system displays one of the following responses.
The following faults result in system shutdown, i.e. all output stages are deenergized:
^ Fault in the front axle stabilizer bar
^ Fault at the front axle pressure sensor
^ Fault in the pressure buildup (pump, pressure limiting valve on the front axle)
^ Fault in the control unit
^ VIN is not sent via the CAS / omitted / incorrect
^ Direction-valve position fault, faulty selector-position recognition sensor
^ No PTCAN signal
The deenergized fail-safe valve shuts off the chambers of the active stabilizer bar. A fluid compensation is only performed by way of internal leakage of the oscillating motor and the valve block. The nonreturn valves in the valve block permit additional suction of fluid so that no cavitation occurs in the front axle oscillating motor.
The chambers of the rear axle oscillating motor must not be shut off. The handling corresponds virtually to that of a conventional vehicle. The crossover to the fail-safe status can also be controlled in the event of extreme maneuvering.
Restricted Control Comfort
A lateral acceleration is calculated from the road speed and steering wheel angle from the CAN signals. This signal is faster than the actual lateral acceleration and compensates the time delay of the hydromechanical system. In the event of a fault in these two signals, the system responds with a delayed roll compensation. This arises only in the case of extremely quick steering maneuvers and is barely noticeable in normal cornering maneuvers.
In the event of a faulty lateral acceleration sensor, the lateral acceleration is calculated exclusively from the CAN signals. No impairment of function can be detected by the customer.
In the event of a fault in the rear axle circuit, i.e. a stabilization at the front axle only, the customer notices that the vehicle is subject to larger rolling motions. Agility diminishes at road speeds < 120 km/h.
The system also responds if the fault Fail-safe valve stuck open is detected in the predrive check.
An electrical fault in the rear axle pressure sensor may result in minor failures in roll angle compensation. To be on the safe side, slightly more stabilizing torque is exerted on the front axle than in normal operation. This can be felt by the driver.
Restricted System Monitoring
Dynamic Drive receives via PTCAN the following sensor signals from DSC and SZL:
^ Lateral acceleration
^ Yaw velocity
^ Road speed
^ Steering-wheel angle
These signals are used to check the lateral acceleration sensor.
Dropout of the engine speed signal (DME) results in restricted control comfort.
In the event of a fault in the lateral acceleration and yaw velocity CAN signals, the system is lacking two items of redundant information. Since this information is used exclusively for checking the other signals, the Dynamic Drive function is preserved with full control comfort.
Although the Dynamic Drive function is not impaired, the driver receives the display Chassis control comfort restricted. He/she is prompted to visit a garage/workshop at the next available opportunity.
A dynamic driver will notice the absence of the steering angle signal.
The warning messages must be acknowledged by the driver. Each warning message goes out only after it has been acknowledged.
Once the cause of the fault has been rectified, the control unit can be returned to full function.
There are two reset conditions depending on how fast a fault is to be detected:
^ All faults which are no longer present are reset with ignition off. It is necessary here to wait until the sleep mode has been obtained before ignition on is activated again.
^ Sporadic faults which can mostly be traced back to communication faults in the CAN bus are then automatically reset while the vehicle is moving straight ahead or stationary provided they have only occurred briefly and rarely. In this case, the customer cannot detect the activation while the vehicle is moving or stationary.
^ The associated faults with important additional information are stored in the fault memory. This additional information contains the kilometer reading/mileage at which the fault occurred, whether the fault is currently present and the frequency with which the fault in question has occurred. Thus, when the vehicle is brought into the garage/workshop, it is possible to carry out a specific analysis of the currently pre sent fault and also an analysis of a sporadic fault.
Programming
The Dynamic Drive control unit is programmed.
Coding
The Dynamic Drive control unit is coded.