Telematic Control Unit (TCU)
The TCU is the transmit/receive unit of the permanently installed telephone. The TCU is configured for GSM dual band and for frequencies 900/1800 MHz. The TCU is connected to the K-bus and thus connected to the other bus systems in the vehicle. The TCU monitors the charge level of the battery (e.g. lithium ion battery) in the Bluetooth handset and controls the recharging process.
Installation Location The Telematic Control Unit (TCU) is located in the luggage compartment on the rear side wall on the left-hand side or on the left-hand side of the bulkhead, except on the E36 Touring. On the E39 Touring, the TCU is installed behind the rear seats, under the luggage compartment floor. On the E85, the TCU is installed on the partition wall next to the video module.
Construction The Telematic Control Unit (TCU) is of a modular construction and configured according to national version and requirements.
| Key | Description | Key | Description |
|---|---|---|---|
| 1 | Bluetooth antenna | 2 | Bluetooth interface |
| 3 | Fault code memory (EEPROM = Electrically Erasable Programmable Read-Only Memory) | 4 | Working memory (SDRAM = Synchronous Dynamic Random Access Memory) |
| 5 | Data memory (FLASH) | 6 | K-bus interface (body bus) |
| 7 | Transmit/receive button | 8 | K-bus |
| 9 | Signal to mute radio (mute signal) | 10 | Interface for radio mute |
| 11 | Power supply | 12 | On-board supply voltage (= terminal 30) |
| 13 | Ignition lock in position 1 (terminal R) | 14 | Earth (terminal 31) |
| 15 | Interface for the SIM card reader | 16 | Signal cables from SIM card holder to interface for the SIM card reader |
| 17 | Loudspeaker | 18 | Hands-free microphone |
| 19 | Audio interface, voice input and output (MUX-DSP module = multiplexer and digital sound processor: electronic switch for selecting channels for voice output and input/DSP) | 20 | Voltage monitoring |
| 21 | Microprocessor | 22 | Transmitter and receiver module for GSM mobile phone network 900/1800 MHz (NAD/GSM = Network Access Device/Global Standard for Mobile Communication 900/1800 MHz) |
| 23 | GSM antenna (Global Standard for Mobile communications) |
The TCU is connected to the vehicle's electrical system by a 54 pin multi-pin connector. The TCU is woken up via the K-bus. The multi-pin connectors have various assignments on the models:
- E39: X18500
- E46: X13599
- E53: X18500
- E85: X14133
| Pin | Type | Description |
|---|---|---|
| 1 | A | Microphone, positive terminal |
| 2 | --- | --- |
| 3 | A | Data line for the SIM card reader |
| 4 |
- | - |
| 5 | E | Data line for SIM card reader, positive terminal |
| 6 | E | Data line for SIM card reader, negative terminal |
| 7 | E | Signal: Wheel speed, front left |
| 8 | E | Signal: Wheel speed, front right |
| 9 | - | - |
| 10 | - | - |
| 11 | A | Switch-on signal for charging electronics in snap-in adapter |
| 12 | - | - |
| 13 | - | - |
| 14 | - | - |
| 15 | E/A | K-bus connection |
| 16 | - | - |
| 17 | E | Terminal 30, power supply; due to pin load capacity, power supply is split between pins 17 and 18 |
| 18 | E | Terminal 30, power supply |
| 19 | A | Microphone, negative terminal |
| 20 | - | - |
| 21 | E | Screen for microphone line |
| 22 | - | - |
| 23 | - | - |
| 24 | - | - |
| 25 | - | - |
| 26 | - | - |
| 27 | - | - |
| 28 | - | - |
| 29 | - | - |
| 30 | - | - |
| 31 | - | - |
| 32 | A | Switch-on signal for the battery charger in the eject box |
| 33 | A | Switch-on signal for the audio system (audio output) if the radio is switched off during an incoming call. |
| 34 | E | Switch signal for compensator (optional) |
| 35 | E | Terminal R |
| 36 | M | Terminal 31, earth |
| 37 | A | Low-frequency signal, loudspeaker positive terminal |
| 38 | A | Low-frequency signal, loudspeaker negative terminal |
| 39 | A | Earth for the Subscriber Identity Module (SIM) (internally connected to pin 36) |
| 40 | - | - |
| 41 | - | - |
| 42 | - | - |
| 43 | - | - |
| 44 | - | - |
| 45 | - | - |
| 46 | E | Cutout signal for the Bluetooth function, e.g. if use of Bluetooth technology is not permitted in a country. |
| 47 | - | - |
| 48 | - | - |
| 49 | - | - |
| 50 | - | - |
| 51 | A | Mute for the audio system |
| 52 | - | - |
| 53 | - | - |
| 54 | M | Terminal 31, earth |
| A = Output E = Input E/A = Input and output M = Earth V = Supply For current specifications regarding pin assignments, please refer to BMW diagnosis system |
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How it works The TCU (Telematic Control Unit) monitors the hands-free mode and charge level of the battery (e.g. lithium ion battery) on the Bluetooth handset. The TCU is connected to the other control units in the vehicle via the K-bus interface.
Microprocessor The microprocessor controls all TCU (Telematic Control Unit) functions.
Bluetooth Module The Bluetooth module is an interface between the Bluetooth handset and the TCU. The information is transferred between the Bluetooth handset and the TCU via the Bluetooth antenna connected to the TCU.
K-Bus Interface The Telematic Control Unit (TCU) is connected to the K-bus (body bus) via the K-bus interface. The K-bus interface controls transmitting and receiving between the control units and the electronics during data exchange. Data (see below) is transferred via the K-bus, e.g:
- Entries in the phone book (phone numbers)
- Audio signals (voice)
Interface For Radio Mute The interface for radio mute deactivates the signal output from the radio when hands-free mode is active. In hands-free mode, the radio mute function ensures that only the voice information from the hands-free microphone and to the loudspeakers are processed.
Power Supply The power supply generates the supply voltage for the Telematic Control Unit (TCU) from the on-board supply voltage (terminal 30). The power supply is switched on and off with terminal R.
Voltage Monitoring Voltage monitoring monitors the voltage and recharging of the battery (e.g. lithium ion battery) in the Bluetooth handset. If there is insufficient voltage in the vehicle electrical system, voltage monitoring switches off the power supply.
Subscriber Identity Module (SIM) The interface to the eject box is used to read data from the SIM card. The Telematic Control Unit (TCU) recognises the GSM mobile phone network via the SIM card inserted in the SIM card reader on the eject box. The Professional car phone is then activated for this GSM mobile phone network.
Multiplexer/Digital Sound Processor (MUX/DSP) The module has the following functions:
- A Multiplexer (MUX, Electronic Switch) For Selecting The Channels For Voice Output
- A Digital Sound Processor (DSP) For Hands-Free Mode
- Voice Recognition For Telephone Functions
Transmitter And Receiver Module NAD/GSM 900/1800 A transmitter and receiver module NAD/GSM (Network Access Device/Global Standard for Mobile Communication) is installed in the Telematic Control Unit TCU). The NAD/GSM operates on frequencies 900/1800 MHz. The NAD/GSM transmitter and receiver module enables the GSM mobile phone network of various network providers to be used. (In Germany, e.g. the GSM mobile phone network with network providers D1/D2 and E-Plus.) Information is transferred between the GSM mobile phone network and the NAD/GSM 900/1800 via the Bluetooth antenna connected. The transmitter and receiver module also contains an interface for the emergency call button. (The emergency call button is displayed on the on-board monitor or on Central Information Display, etc.)