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The ABS system goes through self tests when the vehicle first starts up and again when the vehicle begins to move. These tests can narrow down where the problem is.
When the engine is started and before the vehicle moves, the computer runs through a continuity test on all of the components. This checks the wiring, connections, sensors and components. So if the light comes on right away, the system has detected a bad component or wiring problem.
Another test is performed when the vehicle gets to about 6-8 mph and the brake is not applied. This tests the motor, valves and the sensors for equal signals. So if the light comes on then, the most likely fault is a sensor, but it could be other things as well.
If the brakes were worn to the point that they went metal to metal, one of the sensors could be giving weak signals because of metal filings sticking to the sensor.
This isn't an easy one to answer because there are a number of things that could fail. The cruise control is designed to turn off if there is any fault detected with the brakes so don't worry about that, fixing the ABS will fix the cruise.
This system (like everything on a Saab) is a complicated and sophisticated system. You need some diagnostic equipment to do any real repairs. If something special happened on one of the wheels, like a snow chain coming off, accident, recent brake work, you could replace the wheel speed sensor on that wheel. But other than that, it's going to have to go into a shop that works on Saabs.
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