In general, ABS light on + rough idle = no power to the CIS-E and ABS ECUs, and Idle Control Valve.

All three are powered through the OVP relay. Check the fuse mounted right on it's top, and if OK then check the connections at the pins inside the OVP itself, as it is a well known problem that the connections develop hairline cracks over time. You just need to resolder them to correct the problem.

You can also try rocking the OVPR a bit in and out of the socket and see if the problem comes and goes. If it does, it's a sure sign that the internal connections are going intermittent.

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W163 ML230 EURO SPEC 1999
W124 300E 1986