the ABS unit consists of 3 parts, the PCB electronics, the valve block and the motor pump.
each of the PCB/control units (
/ABS-Traction Control/AirBag/DashClocks/Steering Lock) are pre-programmed to the chassis number of the car it is fitted to at time of manufacture.
they are not reprogrammable so cannot be just swapped over.
If they have to be replaced by Renault then a pre-configured or blank-(program on 1st connection) has to be fitted as they share data on the various CAM Buses running through the car wiring loom.
the valve block and motor can be changed over, though the valve block is probably going to be messy to disassemble (as its full of brake fluid.)
it is highly probable that some of the driver chips and other components on the PCB can be removed and fitted on the faulty part (by an experienced electronics technician.)
there is also the possible problem that you may have a fault on the wiring loom as it passes though the firewall into the engine bay, across the right of the engine bay under the battery compartment and down to the ABS unit.
reno's have problems across all models with this(even brand new cars on ocasion), caused by poor solder/crimp joints(manufacturing issues), excessive vibration causing fracturing of the wires or corrosion due to water/salt ingress.
if the under engine/wheel arch splash guards are missing then the probablity of an electrical failure is increased substantially.
before you start ripping the ABS apart, have you had the diags codes read off the
, the fault may be from a wheel sensor.
if they still cannot read them then there is most likely a wiring problem in the engine bay.
the first step is to disconnect the wiring connector, wd40 the connectors, refit then test the system.
if still no go, then look at swapping the motor unit and inspect the valve block whilst changing over as well as an inspection of the electrical connectors.