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Electronic brake force distribution

The ABS control module (w/EDL) -J104- is programmed with specially designed software for "electronic brake force distribution", which takes over the function of brake pressure limiter.

In the event of failure of the ABS, the signal which activates the ABS/EDL warning light and the brake system warning symbol is sent to the instrument cluster via the wire from contact 21 of ABS control module (w/EDL) -J104-. In vehicles built up to week 20/1997, the instrument cluster simply registers whether or not this signal is present: The brake system warning symbol normally comes on in addition to the ABS/EDL warning light.

In vehicles built from week 21/1997 onward, the brake system warning symbol no longer comes on at all times when a failure of the ABS has occurred. 

In cases where a failure of the ABS has occurred, but the electronic brake force distribution function can still be maintained by a back-up feature, the signal sent to the instrument cluster is pulsed. The instrument cluster distinguishes between three conditions: no signal present, pulsed signal, and continuous signal present. The ABS/EDL warning light and the brake system warning symbol come on in accordance with the signal received.

Fig 1: Identifying ABS/EDL Warning Light And The Brake System Warning Symbol
G02732398Courtesy of AUDI OF AMERICA, INC.
  1. Terminal 15
  2. Signal for activation of ABS/EDL warning light and brake system warning symbol
  3. Supply voltage for ABS/EDL warning light
  4. Supply voltage for brake system warning symbol
  1. During phase "A" (after ignition is switched on) the ABS/EDL warning light is activated for two seconds during the self-test by means of signal "2", and comes on. During this phase an internal function in the instrument cluster suppresses the activation of the brake system warning symbol.
  2. During phase "B", signal "2" is not present. The ABS/EDL warning light and brake system warning symbol do not come on.
  3. In phase "C", On Board Diagnostic (OBD) has detected a malfunction which does not cause the electronic brake force distribution function to be switched off. Signal "2" is pulsed. Only the ABS/EDL warning light comes on.
  4. In phase "D", On Board Diagnostic (OBD) has detected a malfunction which causes the electronic brake force distribution function to be switched off. Signal "2" is present continuously. Both the ABS/EDL warning light and brake system warning symbol come on.

If the brake system warning symbol comes on, this indicates that the electronic brake force distribution function has failed. In this condition the vehicle should only be driven with extra caution. See  TROUBLESHOOTING ABS AND ESP, SAFETY PRECAUTIONS AND GENERAL NOTES   , Road testing. 

For further information on the activation of the warning lights in connection with the electronic brake force distribution function, see WARNING LIGHT FUNCTIONS OVERVIEW  , table of warning light functions. Refer to the notes in the table under CHECK CONTROL MODULE VERSIONS  for identification of what type of electronic brake force distribution function is installed in the vehicle.

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