Technician A is not correct, while Technician B is correct.
In a vehicle with antilock brakes, pumping the brake pedal rapidly can actually interfere with the operation of the antilock system and can cause the wheels to lock up. The proper technique when braking with antilock brakes is to apply firm and steady pressure on the brake pedal, without pumping it. This allows the antilock system to work as designed, preventing wheel lock up and maintaining traction and control.
If the brake pedal is pumped rapidly and repeatedly, the ABS warning lamp may turn on, indicating a fault in the ABS system. Additionally, this action can set a Diagnostic Trouble Code (DTC) and can disable the ABS system, causing it to revert to a traditional braking system.
Therefore, Technician B is correct in stating that rapidly pumping the brake pedal may turn on the ABS warning lamp, set a DTC, and disable the ABS system.