Couple of common issues for you to check out first :
Wheel Speed Sensor Circuits
1. Ensure ignition switched off
2. Disconnect ECU multi-plug
3. Connect ohmmeter between harness multi-plug terminals listed below:
o LHF: 7 and 25
o RHF: 5 and 23
o LHR: 4 and 22
o RHR: 6 and 24
4. Resistance should be 900 to 1400 ohms
5. If resistance not as specified:
o Disconnect the appropriate wheel sensor from the car loom.
o Measure resistance across wheel sensor at plug on end of sensor.
o If outside above range, replace wheel sensor.
o If OK, check wiring between sensor connection and ECU.
Checking the Low Brake Fluid in Reservoir Warning
1. Remove the 2 pin connector from the brake fluid level reservoir. Ignore the 3 pin connector.
2. Without removing the reservoir cap, check for continuity across the 2 connector terminals on the cap. Lack of continuity across these terminals indicates low brake fluid, and disables the ABS.
3. If no continuity, top up reservoir with brake fluid as required. If fluid level OK but no continuity, buy a new cap. As a short term measure to diagnose reservoir cap failure, bridge the terminals of the wiring loom connector that fits to the cap with a short piece of wire and test drive.
Let us know how you get on.