My OEM scanner gives me the option to command the ABS system to do something important while bleeding brakes.

In the past (before I owned this scanner) I seemed able to bleed the brakes fine on the vehicle. What would activating this feature on the scanner do for me while bleeding brakes?

2 Answers 2


There is brake fluid trapped in the ABS pump and lines associated with it. Unless you cycle the pump and move that fluid out, it's still the old possibly old fluid. There may also be air trapped in the pump if you opened up the system.

The brake bleeding function is useful and often important to get an ABS-equipped brake system operating normally.


I have had to use this function when refilling/bleeding COMPLETELY empty brake systems.

Essentially when the ABS pump is dry it is unable to pump (airlocked) so despite you getting fluid out of all 4 brake lines you may still have air in the pump. This function is designed to run the pump to purge itself, which would not happen during a normal manual bleed.

  • Do you have to toggle this function intermittently on the scanner? Or just set it "ON" and bleed the brakes normally?
    – TSG
    Mar 27, 2023 at 12:39
  • @TSG - In my case yes I had to do one wheel at a time, open the calliper nipple, run the pump, till it flowed clear, and move round. There was a specific order. Mar 28, 2023 at 12:43
  • I didn't realize it actually pumped electrically (I thought I would still have to push on the brake pedal).
    – TSG
    Mar 28, 2023 at 17:14

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