Retractable Hardtop E89 (CTM Convertible-Top Module)
Retractable Hardtop
A retractable hardtop is used in the new BMW Z4 Roadster (E89). The two-part roof panel 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. 20 seconds.
A central hydraulic unit drives the retractable hardtop. whereby the hardtop is moved by 4 hydraulic cylinders. An electric motor unlocks and locks the convertible top 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 convertible top can be operated using 2 buttons in the centre console switch cluster. A total of 13 sensors monitor the sequence of movements. The Convertible Top Module (CTM) monitors and controls all movements.
IMPORTANT: Emergency actuation only in service.
Emergency actuation of the retractable hardtop for the customer is not implemented. However, emergency actuation is possible in Service. The emergency actuation is described in detail in the repair instructions.
Brief description of components
The following components are described for the retractable hardtop:
Sensors on the retractable hardtop
In total, 5 Hall sensors and 8 micro switches are installed as sensors for the Convertible Top Module (CTM).
The Hall sensors and micro switches help the CTM detect the position of the convertible top. This means that after loss of terminal 30 or emergency actuation the retractable hardtop can still be operated without re-initialization.
NOTE: Micro switch, 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 switch cluster is equipped with 2 buttons ('open convertible top' and 'close convertible top') for convertible 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 climate control (IHKA) to the centre console switch cluster.
The green LED lights up during opening or closing. The red LED indicates incorrect operation or incorrect conditions (e.g. luggage compartment partition has not been lowered). The red LED flashes as soon as the hardtop is in an intermediate position and there is no operation at that 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 feature of button for operation.
The fault code A6A4 is stored under the following conditions:
- Terminal R On while the button is pressed
- After finished 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 module for all functions of the retractable hardtop. The installation location 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 modules. In this way, e.g., information on the outside 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 module for the power windows.
In certain situations, the CTM provides information in the instrument cluster as Check Control messages.
Drive unit for hardtop lock
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 center. A rotating disk and thrust rods move the catches to the right and left. The two Hall sensors 'cowl panel locked' and 'cowl panel unlocked' monitor the locking.
NOTE: 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 detent. In the event of a crash, the stored hardtop cannot fold forwards.
Hydraulic unit
The hydraulic unit is located in a recess in the base of the luggage compartment.
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 creates 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 memory 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.
KOMBI: Instrument cluster
The instrument cluster delivers the outside temperature (bus signal). The instrument cluster 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) actuates 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 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 power 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 module 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 window movement with the convertible top in an intermediate position. The Car Access System (CAS) controls convenience opening of the convertible top. The signals from the remote control 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 distribution box in the junction box 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 power supply from the junction box is interrupted, adequate communication with the BMW diagnosis system is still possible.
Antenna diversity
Depending on whether the roof is closed or opened, the CTM sends a signal to the antenna diversity. The antenna diversity then changes over the antennas 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
- Soft Close Automatic system
Opening and closing the retractable hardtop
To open and close the retractable hardtop, the following conditions must be met:
- terminal R is ON
- Outside temperature above -20 °C
- Luggage compartment lid (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 position)
- Unlock hardtop at the cowl panel
- Switch off heated rear window (via the junction box electronics)
- Unlock and open rear module
- Pack roof panel 2 on to roof panel 1.
- Store roof panel package in the rear module and lock
- Close and lock rear module
- Close side windows
Automatic closing of the convertible top takes place in reverse order.
NOTE: Bear the national version in mind.
Closing the side windows is encoded 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 control as well as the mechanical key in the door lock. In the case of vehicles with the "Comfort Access" optional extra, 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. when large items of luggage are loaded. The convenience function is activated as follows:
- Briefly press the luggage compartment button on the remote control
- 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 control are country-specific.
Conditions for operation with the remote control or identification sensor with Comfort Access (optional extra�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 cluster as Check Control messages. On vehicles with a Central Information Display (CID), the short text and supplementary information are displayed.
The Check Control messages provide a better explanation of the red LED on the button, which lights up in the event of a fault. Any Check Control message that is present is displayed every 5 seconds.
Soft Close Automatic 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 drives of the Soft Close Automatic system until the luggage compartment lid 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 information
IMPORTANT: Emergency opening of the 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 actuation of the hardtop only in Service.
Emergency actuation of the retractable hardtop for the customer is not implemented. However, emergency actuation is possible in Service.
The emergency actuation is described in detail in the repair instructions.
IMPORTANT: Vehicle must be stationary.
It is not possible to open and close the retractable hardtop while the vehicle is being driven. On account of the high current consumption of the retractable hardtop of up to 40 Amperes, the hardtop may only be operated when a battery charger is connected or the engine is running. Comply with the additional instructions in the Owner's Manual.
IMPORTANT: There is no anti-trapping mechanism for the rear power windows.
The rear power windows have no anti-trapping mechanism.
This means there is also no one-touch control function for closing the rear windows.
NOTE: No convenience closing via the outer door handle electronics.
On vehicles with Comfort Access, convenience closing is not possible using the outer door handle electronics. Convenience closing is executed via lock cylinders.
NOTE: Maintenance-free hydraulic fluid.
Because of its life-time oil filling, the hydraulic fluid does not have to be renewed. If the hydraulic fluid has to be topped up due to leakage, only the approved hydraulic fluid may be used. Only add hydraulic fluid up to the marking on the oil reservoir.
NOTE: 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 feature of button for operation.
The fault code A6A4 is stored under the following conditions:
- Terminal R On while the button is pressed
- After finished roof movement, button pressed for longer than 20 seconds
The fault code is stored as "not present". The roof is temporarily without function.
After opening once using the button, the roof is operational again.
Notes on encoding / programming
After replacement, the Convertible Top Module (CTM) must be re-encoded.
National 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".
No liability can be accepted for printing or other faults. Subject to changes of a technical nature