Function of ETS control module - GF42.35-P-4500-01B

The 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
  • 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 > 3 km/h above vehicle speed

Switching off condition when one wheel controlled: Wheel speed < 2 km/h above vehicle speed

Switching off condition when 2 wheels controlled: Wheel speed < 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 > 5 km/h above vehicle speed

Switching on condition for second front wheel: Wheel speed > 3 km/h above vehicle speed

Switching off condition for one front wheel controlled: Wheel speed < 3 km/h above vehicle speed

Switching off condition for two front wheels controlled: Wheel speed < 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 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 and cannot be reset by "ignition OFF/ignition ON". After ignition is switched off, the temperature continues to be calculated until a calculated temperature of 30°C is reached, but for a maximum of 30 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 of 7 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 (A1e49 or A1e17) 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 

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.