Mercedes Viano ABS and Traction Control Issues

I had a similar issue with my Audi A6. The ABS light came on and traction control was lost. It was a wheel speed sensor. The ECM uses these sensors to determine wheel speed, and discrepancies can cause ABS and traction control malfunctions. Have you checked the wheel speed sensors for damage or corrosion? It might be cheaper than replacing the control unit. Also, check the sensor wiring.

Thanks. I'm not familiar with inspecting the wheel speed sensors. How do I check them for damage or corrosion, and where are they located? Also, how do I test the signal from the sensor to the ECM?

The wheel speed sensors are near each wheel hub, often on the brake caliper or hub assembly. Look for cracks or frayed wires. Corrosion can affect performance, so look for rust or oxidation. Testing the signal to the ECM requires a multimeter or oscilloscope, but it's complex and requires specialized knowledge. Given your description and the diagnostic reading, if you're not comfortable with advanced diagnostics, consult a qualified workshop. Replacing individual sensors is cheaper than replacing the control unit.

I took the vehicle to a workshop. It was a faulty wheel speed sensor, as you suggested. Replacing it fixed the ABS and traction control issues. Thanks for pointing me in the right direction and saving me money compared to replacing the control unit.