ABS
21T ABS is nothing shy of awesome. It's saved my skin enough times for me to lose count.....on a dry road im sure the deceleration could be measured in G-Force.
I Spent a week or so figuring out how to fix mine and now it works it was all worth it.
Basically you need to figure out if its a sensor fault or a target problem. The sensor points at the target and detects the rotation of the toothed rings. Damage to the rings leads to the ABS computer thinking the wheel has locked and releasing the brakes even under light braking or no braking, it then figures something is wrong and turns the system off. I Suspect this is whats wrong with your car jay as it can be a bit dangerous as before it disarms itll almost turn the brakes off, so unplugging a sensor would keep it permanently off.
Having a sensor out as said above will turn the system off immediately.
So, does your light stay on all the time? Sensor out.
Does your light go out, then reappear usually accompanied with a pulsing in the brake pedal just before hand? Damaged or rusted targets.
Now the best bit.....replacement parts.
Front targets are available from Renault at ?40+ each.
Rears are only available new as part of a whole new rear hub assembly which you should get for about ?70 non OE or ?130ish OE.
Sensors are available but retail at about ?120 EACH :shock:
Second hand is the best option, but finding decent targets is a mare and getting them off the shafts/hubs is even worse as they are interference fit (pressed on). I'm getting pretty good at it but you need certain tools, and a LOT of patience.
Getting second hand semsors is even worse as they sieze into the hubs. Honest to god, they may as well have stuck em in with chemical metal. I Can get them out BUT it requires destruction of the hub around it, thats how bad they stick in. Removing the old sensor also destroys it but as its fooked anyway that dont matter

, alternatively replace the whole hub section with sensor complete.
Also you have to find the dodgy sensor too, which should be possible with a decent digital multimeter and help from a sexpert like me :wink:
Lets put it this way, you'll hate fixing the ABS system, you'll swear and cry and want to give up (probably lol) but goddamn its WELL worth it!!