I had similar issues with the ABS on my '87 BMW and my Silverado. If cleaning the sensor and hub didn't fix it make sure the reluctor (toothed ring) isn't broken. You may have to put a voltmeter on the sensor and spin the wheel by hand to confirm which sensor is the bad one. I'm not sure what the voltage should be for your car, you'll have to look that up. In the case of the Chevy, even a slight build up of rust on the sensor mounting point is enough to increase the gap between the sensor and the reluctor and cause issues. In the case of the BMW, new sensors were cheap enough that I found it was easier to just replace them than try to diagnose them.

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1974 Porsche 914 | 1980 Porsche 911SC
2002 Porsche 911 | 2002 Mitsubishi Montero | 2011 VW Golf