When driving at 50 mph, suddenly the ABS indicator turned on, I turned off the engine and, when starting it again, the indicator was no longer there. One week later, the ABS appeared again. Suspension, brake pads, wheel hubs and drum brakes have been checked but no failure has been found. It was scanned and the failure was indicated to be in the left front ABS sensor, so it was changed but, two days later, the indicator appeared once more. When scanned, the same failure is indicated, so it the left sensor was replaced again and that same day the ABS indicator turned on. I would like to remark that once the indicator appears, I turn off the engine, start it again and it is not there any more. Does anyone have any idea what might be happening?