Electronic Traction Support (ETS)
The Electronic Traction Support (ETS) control module is divided up functionally as follows:
^ Signal conditioning
^ Logic section
^ Safety circuit
^ Additional functions
Signal Conditioning
The following signals are conditioned for the logic section:
- 4 speed sensors
- Stop lamp switch
- Controller Area Network (CAN) data
Logic section
The conditioned input signals are processed in the logic section and converted into output signals.
The logic section is divided up functionally as follows:
- ETS control mode
- Temperature monitoring
ETS Control Mode
The control mode for brake intervention at the rear axle is recognized for the left and right rear wheel from the vehicle speed and ETS slip recognition.
Switching on condition:
Wheel speed greater than 3 km/h above vehicle speed
Switching off condition when one wheel controlled:
Wheel speed less than 2 km/h above vehicle speed
Switching off condition when 2 wheels controlled:
Wheel speed less than 1 km/h above vehicle speed
Speed range:
0-80 km/h
If the switching on condition is maintained during acceleration above 80 km/h, the control mode is continued up to max. 130 km/h,
The control mode for brake intervention at the front axle is recognized for the left and right front wheel from the vehicle speed and ETS slip recognition.
Switching on condition for one front wheel:
Wheel speed greater than 5 km/h above vehicle speed
Switching on condition for second front wheel:
Wheel speed greater than 3 km/h above vehicle speed
Switching off condition for one front wheel controlled:
Wheel speed less than 3 km/h above vehicle speed
Switching off condition for two front wheels controlled:
Wheel speed less than 3 km/h above vehicle speed or both rear wheels controlled
The ETS control mode at the front axle is permitted when the switching on conditions are met in the speed range of 0-40 km/h.
If the switching on condition is maintained during an acceleration above 40 km/h, the control mode is continued up to max. 80 km/h.
Temperature monitoring
In an exceptional case, there is the risk of the brakes overheating due to the dual load of the brake and the ETS control. For this reason the brake lining temperatures are calculated continuously in the control module and when a calculated lining temperature is reached at the respective brake, no further ETS control is permitted until the temperature has dropped again to as set value.
If ETS control is prevented by temperature monitoring, the Brake Assist System/Electronic Traction Support (BAS/ETS) malfunction indicator lamp comes on for as long as the ETS control would be effective, but for at least 5 seconds. The exceeded temperature is also retained in the fault memory.
Temperature calculation
The brake lining temperature is calculated separately for each wheel. it is determined without a temperature sensor. The following inputs are evaluated to calculate brake lining temperature:
- Vehicle speed
- Brake operation
- Calculated brake pressure from the ETS control logic
After-Running Mode After "Ignition OFF"
The voltage supply to the ETS control module is ensured by this operating mode even after "ignition OFF". As a result the brake lining temperatures continue to be calculated arid cannot be reset by "ignition OFF/ignition ON". After ignition is switched off, the temperature continues to be calculated until a calculated temperature of30°C is reached, but for a maximum of30 minutes. The voltage supply to the ETS control module is then switched off.
Safety Circuit
The purpose of the safety circuit is to recognize defective components in the control module and faults in the electrical wiring system. After "ignition ON" and when a speed of7 km/h is exceeded for the first time, system tests are carried out, which recognize faults at the solenoid valves, the high-pressure/return pump and the speed sensors. Constant monitoring is also carried out during ABS or ETS control. If a fault is recognized, the system is switched off and this is displayed to the driver by the BAS/ETS or ABS malfunction indicator lamp (Ale49 or Al e17) coming on. A fault code is also stored in the control module.
The safety circuit also constantly monitors battery voltage. If a voltage of 10.5 V is not achieved the system is also switched off until the voltage is again in the specified range.
Additional Functions
Partial Function Of Speed-Sensitive Power Steering (SPS)
The control module calculates the specified current for actuating the SPS P-valve (Y10) from the vehicle speed which is available internally and the status signal.
Wheel Speed And Speed Status Signal Outputs
^ Wheel speed output: The ETS control module supplies the current wheel speed of each wheel for systems which need a wheel speed signal.
^ Speed status signal output: The ETS control module supplies the speed status signal for systems which need information on the current vehicle status (vehicle stationary, vehicle moving, speed sensor defective).
Malfunction Indicator Lamp Actuation
The signals from the brake pad wear contacts and the parking brake are recorded. They are transmitted to the instrument cluster together with the signals for the ABS and BAS/ETS malfunction indicator and warning lamps via the CAN data bus.
Task
To perform all Antilock Brake System (ABS) and Electronic Traction Support (ETS) brake control functions.
On vehicles with Speed-Sensitive Power Steering (SPS), (S Class (140) and E Class (210) models only) the control module also has the electronic system and control logic required for this.
To supply other systems with the vehicle speed signal, the wheel speed status signal and the stop lamp switch signal. To supply the instrument cluster with the signals for the lamps: ABS Malfunction Indicator Lamp (MIL) (A1e17), ETS MIL (A1e35) or Brake Assist System/Electronic Traction Support (BAS/ETS) malfunction indicator lamp (A1e49) and ETS warning lamp (A1e36). On the control module version LK55/1 or /2 also with the signal for the brake pad wear indicator lamp (A1e6) and low brake fluid level/parking brake indicator lamp (A1e7) via a serial line or Controller Area Network (CAN). In addition on ML model (163): Signal for brake fluid level and fault in the electronic brake booster pressure for activating the low brake fluid level/parking brake/brake booster pressure indicator lamp (A1e7) and the warning buzzer (A1h1)
Design
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There are many versions of the ASR/ETS control module. They can be identified by the housing (e.g. SK 16).
NOTE: For model name/model number cross reference refer to Model Designation Table. Application and ID
SK16 Housing
SL (129) and S Class (140) Models with module box
LK55 Housing
C Class (202) Models up to 08/95
E Class (210.004/010/020/035/O37) Models up to 05/96
E Class (210.053/055 except Japan and USA) Models
Model 210.055 (Japan and USA model year 96)
LKS511 Housing
(shortened housing on vehicles without SPS as of06/96)
C Class (202) models as of 09/95.
E Class (210.004/010/020/035/037) models as of 06/96
E Class (210.055) as of model year 97
All other E Class (210) models as of start of production
ML (163), SLK (170) and CLK (208) as of start of production
SL (129) and S Class (140) models with control module box