Chasing ABS/TC issues

hi guys, I had an issue with my ABS on front left side (broken wires) then sometime later I replaced said hub. now a second issue has appeared with the right hand side so ran a substitute wire straight to the speed sensor and hey presto it bloody worked no more lights on dash. oh yeah this is 2 days before mot so well happy. now 40 mins before mot and I go out for drive to warm out the engine for emissions and there it is the ABS/TC lights come back on!. so quickly got back home plugged it up and it says front left and rear right problems now. checked the wiring all good and needless to say I missed my mot ffs. Any ideas??????Nothing was touched after it was fixed and ABS lights were off.
Not sure you will if abs light is on because it disables abs system. (i could be wrong on that tho)
When you check readings from each sensor (as well as spinning the wheel while measuring readings) jot the figures down to check they all are giving very similar figures, will pin point if any of the sensors are faulty, next stage will be checking all abs related fuses and cleaning abs ecu connector plug with contact cleaner, if that fails then your looking for a broken wire or bad earth.
What codes are coming up with op-com?
All sensors were giving same mph reading, i checked fuses and cleaned the connection block. Im thinking bad earth cause thats the only thing left well or a bad ecu.cant remember specific code just right rear low voltage or something. Can check tomorrow
sometimes fixing problems (especially electrical) un-earths more problems further on, year of the car the wires can become brittle and break up inside, i will check on my vectra tomorrow for sure, but there may be a connector for the speed sensors somewhere near the fuel tank.