Engine Control System Interfaces
Engine Control System Interfaces
Other interfaces
For engine control, the DME control unit requires a few more signals.
Brief component description
The following components are described for the other interfaces:
Accelerator pedal module
The accelerator pedal module detects the position of the accelerator pedal. Using this information, the DME control unit calculates the required position of the throttle valve while taking other criteria into account.
The accelerator pedal module works according the principle of magnetic resistance. Two Hall effect sensors (rotational angle) are used to enable monitoring and fault detection. The two Hall effect sensors are supplied separately with 5 Volts and earth by the DME. Transmission of the sensor signals is also separate. The signals are transmitted as analogue. The DME monitors the two input signals of the Hall effect sensors and compares them for plausibility.
Clutch module
On vehicles with manual gearboxes, the clutch module at the clutch pedal picks up the clutch position (clutch pressed: clutch switch open; clutch not pressed, clutch switch closed). The clutch module comprises the clutch switch and evaluation electronics.
The clutch module is supplied with 12 Volts, terminal R and earth. A signal line leads into the DME. When the clutch pedal is not pressed, the clutch module delivers 12 Volts and when the clutch pedal is pressed it delivers 0 Volts to the DME.
Brake light switch
Two switches are fitted in the brake light switch: the brake light switch and the brake light test switch (redundancy for safety reasons). The signals enable the DME control unit to determine whether or not the brake pedal is depressed.
The brake light switch is supplied with 12 Volts, terminal R and earth. Two signal lines lead into the DME. When the brake pedal is not pressed, the brake light switch delivers 0 Volts and when the brake pedal is pressed it delivers 12 Volts via the signal line to the DME. The brake light test switch delivers the same signals to the DME.
Refrigerant pressure sensor
The refrigerant pressure sensor for the air conditioning system is located in the pressure line of the chiller circuit. In the cooling mode, the refrigerant pressure (high pressure) is sensed by the pressure sensor and evaluated in the DME.
The refrigerant pressure sensor is supplied with 5 Volts and earth by the DME. The information is transmitted to the DME on a signal line. The signal fluctuates depending on the pressure. The measurement range from approx. 0.1 to 0.9 Volts corresponds to a pressure of approx. 0.1 bar (10 kPa) to 35 bar (3.5 MPa). With the signal of the refrigerant pressure sensor and the stored characteristic map, the DME can calculate the pressure in the pressure line of the chiller circuit and, depending on requirements, activate or deactivate the electric fan. The signal to activate or deactivate the compressor clutch is also sent via the PT-CAN to the junction box electronics (JBE).
DME control unit
Important functions of the engine control system with regard to BMW EfficientDynamics are:
- Intelligent generator control
- Automatic engine start-stop function
There are 3 other sensors on the printed circuit board in the DME control unit: a temperature sensor, an ambient pressure sensor as well as a voltage sensor. The temperature sensor provides thermal monitoring of the components in the DME control unit. The ambient pressure is required for calculation of the mixture composition. The ambient pressure falls the higher you go above sea level. The voltage sensor on the printed circuit board of the DME control unit monitors the voltage supply via terminal 87.
The DME control unit is connected to the vehicle electrical system via the engine wiring harness and vehicle wiring harness (3 connector chambers). The DME control unit is connected to the rest of the bus system by the PT-CAN (powertrain CAN) via a gateway. The gateway is the junction box electronics (JBE).
System functions
The following system functions are described:
Electronic immobilizer
The electronic immobilizer is both an anti-theft system and start enable device. On the MINI, a newly developed electronic immobilizer (4th generation) will be introduced. This new development uses a new and modern encryption method.
Each vehicle is assigned a 128-bit secret code. This secret code is stored in a BMW database. This means that the secret code is only known to BMW. The secret code is programmed into the CAS control unit and DME control unit and is locked. When the secret code is in the control units, it can no longer be deleted or changed. This means that each control unit is assigned to a certain vehicle. The CAS control unit and the EWS control unit mutually identify one another with the secret number and the same algorithm.
If the identification data is correct, the CAS control unit activates the starter motor via a relay in the control unit. At the same time, the CAS control unit sends the DME control unit an encoded enable signal (rolling code) for the engine start. The DME control unit only enables the engine start if a correct enable signal is received from the CAS control unit. These operations may result in a slight delay in starting (up to half a second).
Notes for Service department
General notes
NOTICE: Procedure in case of defective control unit.
If the CAS or DME is defective, a certain procedure must be followed. The required control unit must be ordered exactly for the vehicle. For this, the vehicle data (vehicle identification number) is required. An EWS adjustment is not necessary after renewing the control unit.
We can assume no liability for printing errors or inaccuracies in this document and reserve the right to introduce technical modifications at any time.