98 cavalier abs light on

98 2.4 5 speed. My abs light on at 115000 km. Gargage checked all sensors & wiring & said abs computer faulty $860.oo . I didn't replace because lack of 860.oo . 125000km park brake warning light came on. I shut off engine checked brake fluid ok started up and light out until last week 136,000km now both Abs & brake warning on. I took to garage checked harness and sensors they put on scan tool replaced foot pedal brake light switch. Abs & warn light off and abs pulsated when wheels locked up but when engine shut off it was just like before. If I pump the brakes before turning on the ignition & starting then the lights will both stay off but will come on when i move the wheels. I installed a new abs relay and pumped the brakes and the lights stayed off and I could drive it no lights on and abs worked. But as before when i restart it is just like before. I replaced the abs computer with one from salvage 75.00. It worked just as before. I have had a lot of suggestions like replace alternator & battery putting out only 13.5 volts not 14 v , replace all wheel sensors & wire harnesses , all brakes etc. I think it has something to do with the master cylinder putting air in the system. But according to manual you can't bleed the brake motor module unless your abs is working so you can put all the pistons to top which has to be done by a abs scanner. Each time i get someone to read the ABS codes it costs about $100.00. My question is has anybody had a similar problem or got a solution? The car otherwise runs great. I don't mind the abs not working but I don't like a brake warning light on! Thanks for the help