Ok, I will go with the assumption it does have ABS and the master cylinder did indeed go dry. When this happens, it has to be bled with a scan tool to activate the ABS motors so it bleeds out the air trapped in it.
There is a workaround that is successful about 75% of the time.
You will need to use jacks and or jackstands to get all 4 wheels off the ground securely. crank engine
and put in gear and accelerate to about 20mph and repeatedly slam on the brakes
. Repeat about 10 times. This normally activates the ABS motors. Now with the engine idling, rebleed the brakes at all the wheels. Test pedal. If good, then good to go.
If not, then we need to recheck the work to make sure no hoses are twisted, that pads and calipers and rotors are not cocked at an angle. Repair as needed.
If ok, then will will need to do a brake line clamp test. Use vise grips and lightly clamp each rubber brake hose at the 4 wheels about 1/2 up the rubber brake hoses.
Test the pedal. It should be high and firm. If it still drops to the floor, then air in the ABS system and at this point will REQUIRE scan tool computer bleeding.
If firm, then starting at rear, remove one vise grip at a time and retest pedal. At whichever one you remove the vise grip and pedal drops to the floor, that is your problem area - either defective caliper, pads positioned incorrectly, caliper cocked, or rotor cocked at angle.
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