Hard Top: Description and Operation
Retractable Hardtop
Retractable hardtop
A retractable hardtop is used in the new BMW Z4 Roadster (E89). The two-part roof shell construction is made of aluminium using a lightweight construction method and weighs approx. 60 kg.
The roof opens and closes (only with the vehicle stationary) in approx. 22 seconds. New from 04/2012: The retractable hardtop can be opened and closed up to a driving speed of 40 km/h.
A central hydraulic unit drives the retractable hardtop, whereby the hardtop is moved by 4 hydraulic cylinders. An electric motor unlocks and locks the hardtop at the cowl when it is closed and when stored in the rear module. The rear module opens and closes via 2 other hydraulic cylinders. The top can be operated using 2 buttons in the centre console control panel. A total of 13 sensors monitor the sequence of movements. The Convertible Top Module (CTM) monitors and controls all movements.
IMPORTANT: Emergency backup operation exclusively for service use.
Emergency activation of the retractable hardtop for the customer is not implemented. However, emergency activation is possible in Service. The emergency activation is described in detail in the repair instructions.
Brief component description
The following components are described for the retractable hardtop:
Sensors on the retractable hardtop
In total, 5 Hall effect sensors and 8 micro switches are installed as sensors for the Convertible Top Module (CTM).
The Hall effect sensors and micro switches help the CTM detect the position of the soft top. This means that after loss of terminal 30 or emergency activation the retractable hardtop can still be operated without re-initialization.
Notice: Microswitch, break in rear module closing operation
This micro switch helps implement a temporary closing power limitation of the rear module. Here, an air gap of 3 cm between the rear module and body remains for approx. 1.5 seconds.
Button for operation
The centre console control panel is equipped with 2 buttons ('open soft top' and 'close soft top') for soft top operation. These buttons are hard-wired to the CTM. If the button is released during the movement, the motion of the retractable hardtop or side windows stops immediately. The function display on the button has 2 LEDs (red and green). The LEDs are activated by the CTM via the K-CAN.
Signal path: Junction box electronics (JBE) and integrated automatic heating and air conditioning system (IHKA) to the centre console control panel.
The green LED remains lit during the opening and closing processes. The red LED indicates incorrect operation or incorrect conditions (e.g. luggage compartment partition has not been lowered). The red LED flashes when the hardtop is in an intermediate position provided that no user control entries are being made at the same time. Flashing does not indicate a fault.
The flashing LED is draws attention to the fact that the vehicle must not be driven in this state.
Important Special characteristic of control button.
The fault code A6A4 is stored under the following conditions:
- Terminal R On while the button is pressed
- After concluded roof movement, button pressed for longer than 20 seconds
The fault code is stored as "not present". The retractable hardtop is temporarily inoperative. After opening once using the button, the retractable hardtop is operative again.
CTM: Convertible-top module
The Convertible Top Module (CTM) is the central control unit for all functions of the retractable hardtop. The installation position of the CTM is in the luggage compartment on the right. The CTM controls the retractable hardtop, the rear module and the Soft Close Automatic system as well as the drive for hardtop locking. The CTM also controls the hydraulic pump and the 6 hydraulic cylinders via the 3 valves in the hydraulic unit. The CTM is connected by the K-CAN to other control units. In this way, e.g., information on the ambient temperature, driving speed and status of the luggage compartment lid is received via K-CAN. On opening and/or closing the hardtop, the CTM sends a signal to the Car Access System (CAS). The CAS is the master control unit for the power windows.
In certain situations, the CTM provides information in the instrument panel as Check Control messages.
Drive for hardtop locking
An electric motor with gear locks and unlocks the hardtop with cowl panel at the windscreen frame. The CTM activates the drive.
The drive is arranged in the centre. A rotating disk and thrust rods move the catches to the right and left. The two Hall effect sensors 'cowl panel locked' and 'cowl panel unlocked' monitor the locking.
NOTICE: The drive has an additional function.
With the hardtop opened, the drive locks the hardtop on the base plate in the rear module. The purpose of this function is crash locking. In the event of a crash, the stored hardtop cannot fold forwards.
Hydraulic unit
The hydraulic unit is located in a recess in the luggage compartment floor. The corresponding valve positions and direction of rotation of the hydraulic pump determine the direction of movement of the hardtop and of the rear module. The direction of rotation of the hydraulic pump is controlled by 2 relays. The hydraulic pump generates an operating pressure of 150 to 200 bar.
In order to prevent the hydraulic pump from overheating if the hardtop is operated frequently, the temperature in the hydraulic pump is measured. The temperature sensor is connected to the CTM by 2 wires without ground. A break in wiring leads to a fault entry. As of 90 °C, a closing movement of the hardtop that has already started is continued up to the safe end position. At 105 °C, the movement of the hardtop is stopped immediately. When the temperature falls below 90 °C, the movement can be continued. The hydraulic unit is safeguarded by a slow-acting fuse of 50 Amperes.
Instrument panel: Instrument panel
The instrument panel delivers the ambient temperature (bus signal). The instrument panel uses the Check Control symbol to display the Check Control messages for the retractable hardtop.
FRM: Footwell module
The footwell module (FRM) activates the front power windows. To open the hardtop, the side windows must be lowered (bus signal from CTM).
JBE: Junction Box Electronics
The junction box electronics (JBE) activate the rear power windows. To open the hardtop, the side windows must be lowered (bus signal from CTM). The junction box electronics deliver the signal as to whether the luggage compartment lid is closed (bus signal).
The power distribution box in the junction box electronics supplies the CTM with terminal 30g.
In addition, the CTM is supplied with terminal 15 by the Car Access System (CAS). If, for example, the voltage supply from the junction box is interrupted, adequate communication with the BMW diagnosis system is still possible.
CAS: Car Access System
The CAS is the master control unit for the power windows. Following a request from the CTM, the CAS ensures that the side windows are opened or closed as the case may be. The CAS also prevents opening of the luggage compartment lid and any power windows movement with the soft top in an intermediate setting. The Car Access System (CAS) controls convenience opening of the soft top. The signals from the remote key are received by the FBD receiver and forwarded to the CAS.
Convenience opening and convenience closing via the lock cylinder in the driver's door: the CAS receives the signal from the footwell module (FRM). The power distribution box in the junction box electronics supplies the CTM with terminal 30g. In addition, the CTM is supplied with terminal 15 by the Car Access System (CAS). If, for example, the voltage supply from the junction box is interrupted, adequate communication with the BMW diagnosis system is still possible.
Diversity aerial
Depending on whether the roof is closed or opened, the CTM sends a signal to the aerial diversity. The aerial diversity then changes over the aerials accordingly.
System function
The following system functions are described for the retractable hardtop:
- Opening and closing the retractable hardtop
- Convenient operation and convenient loading
- Check Control messages
- Automatic Soft Close system
Opening and closing the retractable hardtop
To open and close the retractable hardtop, the following conditions must be met:
- terminal R is ON
- Ambient temperature above -20 °C
- tailgate (rear module) closed
- Vehicle stationary (driving speed 0 kph)
- Luggage compartment partition lowered
- Lateral inclination of the vehicle less than 11 °
- power windows are initialized
- battery voltage greater than 11.5 volts
- Fewer than 5 opening and closing operations in succession
- Temperature of the hydraulic fluid for opening maximum 90 °C and for closing maximum 105 °C
Automatic opening runs as follows:
- Lower side windows (if closed or in intermediate setting)
- Unlock hardtop at the cowl panel
- Switch off heated rear window (via the junction box electronics)
- Unlock and open rear module
- Pack roof shell 2 on to roof shell 1.
- Store roof panel package in the rear module and lock
- Close and lock rear module
- Close side windows
Automatic closing of the soft top takes place in reverse order.
NOTICE: Bear the national version in mind.
Closing the side windows is coded on a country-specific basis.
Convenient operation and convenience function for loading and unloading the luggage compartment
The retractable hardtop can be operated using the remote key as well as the mechanical key in the door lock. In the case of vehicles with the "Comfort Access" optional equipment, the hardtop can be opened and closed using the identification sensor.
The new convenience function for loading and unloading enables rapid access to the luggage compartment when the roof is open, e.g. if large pieces of luggage are loaded (only with Comfort Access option 322). The convenience function is activated as follows:
- Briefly press the luggage compartment button on the remote key
- Then press and hold down the luggage compartment button (no more than 1 second may elapse between releasing and pressing again)
First of all, the rear module is unlocked and completely opened. Then the roof package is swung out of the luggage compartment. Subsequently, the rear module is closed and locked. The luggage compartment lid is unlocked via the Soft Close Automatic system. Here, the luggage compartment lid opens slightly.
The convenience functions via the remote key are country-specific.
Conditions for operating with the infrared remote key or ID sensor with Comfort Access (SA 322)
Check Control messages
In certain situations, it is not possible to open or close the hardtop. The corresponding messages are displayed in the instrument panel as Check Control messages. On vehicles with a Central Information Display (CID), the short text and supplementary information are displayed.
The Check Control messages serve to explain in closer detail the red LED on the button which lights up in the event of a fault. A Check Control message is displayed every 5 seconds.
Automatic Soft Close system
For convenient closing of the luggage compartment lid, the Soft Close Automatic system is installed as-series standard. The Soft Close Automatic system consists of 2 drives. The drives lock the luggage compartment lid on the left and right at the support member of the rear module. This increases the stability of the rear end.
When the luggage compartment locks on the left and right have reached the locking bracket, 2 micro switches are pressed. The signals are sent to the junction box electronics (JBE). The Convertible Top Module (CTM) receives the signals across the CAN bus. The CTM then activates both drive units for the Automatic Soft Close system, continuing until the tailgate is locked.
Banging the luggage compartment lid shut would make closing with the Soft Close Automatic system unnecessary. For reasons relevant to safety, it must be ensured that the luggage compartment lid really is closed. This is why the drives of the Soft Close Automatic system are activated in all cases.
Both drives have an anti-repeat circuit to prevent overheating. The anti-repeat circuit permits up to 20 activations of the Soft Close Automatic system (counter up to 20 increments). Thereafter, the Soft Close Automatic system is electrically blocked for approx. 2 minutes.
Notes for Service department
General notes
IMPORTANT: Emergency opening of rear module
The elimination of the lock cylinder and of the Bowden cable means that if the luggage compartment lock is defective there is no emergency release for the luggage compartment lid. At the same time, the unknown status of the luggage compartment lid means that movement of the hardtop is blocked.
In Service, a test module can be used to open the rear module. In this test module, the block conditions for the luggage area cover and luggage compartment lid are ignored.
IMPORTANT: Emergency activation of the hardtop only in Service.
Emergency activation of the retractable hardtop for the customer is not implemented. However, emergency activation is possible in Service. The emergency activation is described in detail in the repair instructions.
IMPORTANT: Vehicle must have a date of manufacture before 04/2012.
It is not possible to open or close the retractable hardtop while the vehicle is being driven. Due to the high power consumption of the retractable hardtop of up to 40 amperes, the hardtop may only be operated with a battery charger connected or with the engine running. Comply with the additional information in the Owner's Handbook.
IMPORTANT: No finger-protection feature is installed on the rear power windows.
The rear power windows have no anti-trapping protection. This means there is no toll function for closing the rear windows either.
NOTICE: No convenience closing using outside door handle electronics.
On vehicles with Comfort Access, convenience closing is not possible using the outside door handle electronics. Convenience closing is run via lock cylinders.
NOTICE: Zero-maintenance hydraulic fluid.
The hydraulic fluid does not have to be changed because the system is filled with life-time fluid. If, as a result of a leak, hydraulic fluid needs to be topped up, always use the approved grade of hydraulic fluid. Pour in hydraulic fluid only up to marking on oil reservoir.
NOTICE: If excessive noise is generated, bleed the hydraulic system.
If excessive noise is generated while the hardtop is moving, the hardtop must be opened and closed several times. This will automatically bleed the hydraulic system in the oil reservoir.
Diagnosis instructions
IMPORTANT: Special characteristic of control button.
The fault code A6A4 is stored under the following conditions:
- Terminal R On while the button is pressed
- After concluded roof movement, button pressed for longer than 20 seconds
The fault code is stored as not present . The roof is temporarily inoperative. After opening once using the button, the roof is operative again.
Notes on encoding/programming
After replacement, the Convertible Top Module (CTM) must be recoded.
National-market versions
Bear in mind the different national versions for the convenience functions: see section "Convenient operation and convenience function for loading and unloading the luggage compartment".
We can assume no liability for printing errors or inaccuracies in this document and reserve the right to introduce technical modifications at any time.