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STEP 3: Blink code identification and system response

  1. If you already know how to read ABS Blink Codes from the ECU in question, please go straight to STEP 4: Blink code list
  2. If you are unsure how to read ABS Blink Codes from the ECU, start by familiarising yourself with the diagram below, and then, where appropriate, follow the step by step procedure in the table
  3. Please ensure all necessary Health and Safety precautions are implemented before commencing any repair work

Knorr-Bremse CI12 System ECU



System Response

Notes / Comments



Connect a switch (Diagnostic Push Button) between the pin labelled 'DIA L' (XI/14) of the ECU and Ground.



Blink Code display (i.e. a sequence of flashes) may be initiated.

The Blink Code will be displayed on either the Dashboard ABS Warning Lamp (INA) or the Traction Control Warning Lamp (ASR). Consult the Vehicle Manufacturer’s Handbook to establish which lamp is used and where it is located.






Switch Ignition ON (ECU powered).

Wait at least 1 second,

Then press Diagnostic Push Button for between 2 and 5 seconds,

Then release button.

The ABS Indicator Lamp will illuminate whilst the button is pressed, and go out when it is released.

The Blink Codes are displayed in blocks of flashes of the ABS Indicator Lamp.

The first time the Diagnostic Push Button is pressed for between 2 and 5 seconds, subsequent to that described in Column 2 of this row (Step II), the configuration code is displayed (see diagram above).

Following this, if the button is pressed again for between 2 and 5 seconds, the first recorded fault is displayed (i.e the most recently detected fault).

Further Blink Codes can be displayed by additional activation / pressing of the Diagnostic Push Button (for between 2 and 5 seconds).

See Step III below for how to interpret the ABS Indicator Lamp flashes.



Count the flashes from the ABS Indicator Lamp each time the Diagnostic Push Button is pressed to determine the Blink Code(s).

Write down only the first 4 or 5 Blink Codes for faults recorded on the ECU (there may be several stored in the memory).

Following each activation of the button, a period of approx. 3 seconds elapses before the Blink Code is displayed.

The Blink Code for a fault is in three parts 'hundreds', 'tens' and 'units'. The flashes for the 'hundreds', 'tens' and 'units' are all of the same duration, and are separated by a delay of approx. 3 seconds (see diagram above).

The ECU is able to store up to 16 different faults.

After the final Blink Code has been displayed, further pressing of the Diagnostic Push Button will result in the first fault being repeated.

If the Service Brake has not been actuated after power up, this will be shown as a Brake Light Switch (BLS) fault.



Turn Ignition OFF

Determine if faults recorded in III above are active or stored:





Active Faults: Will reappear (repeat) after any Blink Codes have been deleted from the ECU.

Stored Faults: Will be cleared when Blink Codes are deleted from ECU.

NOTE: Last fault stored is first fault displayed.




Clearing ECU fault memory:

Whilst pressing the Diagnostic Push Button, switch ignition ON, and hold button for a further 3 seconds.

Release button and the memory is cleared.

The ECU self-configures after the memory has been cleared.

The ECU self-configures to the status of the system at the time of ‘powering up’ and so any component connected after configuration has taken place will not be recognised by the ECU.





Turn Ignition OFF






Repeat steps II and III above.

Record Faults (Blink Codes).

Only active faults will be shown now.


To identify blink codes, refer to the Blink Code List. Make the necessary repairs to active faults. Repeat Step V (Clearing ECU fault memory), then road test the vehicle. The warning light should go out.

If the warning light remains after road testing, go back and repeat steps II , III and VII again until the warning light does go out.

NOTE: If the Service Brake has not been actuated after power up, this will be shown as a Brake Light Switch (BLS) fault. Operation of the BLS is required to inform the ECU that the brake is applied (required to enable differentiation between ABS and ASR modes).

Record faults for future reference.

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