Pontiac Repair: brakes locking up

Question
97 transport 3.4l, locks up after half km....no warning lights on...put on hoist & all 4 wheels locked, NO codes given.. so bled front drivers clipher & it worked...next day drove 1 km Before brakes locked up...bled abs booster & drove home ...Do I need Dealer's code reader to get codes ??
What can i do next ??

Answer
Hi Andrew sorry for the delay I never got notification of the question till now. it's not going to be an ABS issue you either have a bad master cylinder or someone added non brake fluid to the brake master cylinder any kind of oil added to it will make the seals swell in the master cylinder and in the wheel cylinders and calipers. a good indication that would be the boot on the fill cap if it's bloated up and swelled up that is a tell tail sign of an oil was added to the brake fluid. you need a code reader to get ABS codes there is no way to flash them like a check engine light for a engine computer.