1991 corvette. The antilock brakes are activating when they should not be. When I apply the brakes usually at low speed(10-20mph) dry ground under no stress situation the brakes will activate. Doesn't do it everytime, very random in occurance. I have noticed no particular pattern except sometimes the ABS light will come on for a couple of seconds at random times as well when I am not applying brakes. My Chevrolet dealer has not been able to find the problem. Any ideas where to go from here.
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Re: anti lock brakes activation
If abs activates when it should not,,, it means abs module senses one or more wheel sensores under 3 mph and the other sensores are above 3 mph. .the cause of this is usualy a bad wheel speed sensor or excessive air gap between the sensor and ringwheel. you need an abs data scanner to hook up and go for a test drive to find out which sensor is the culprit.
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Condition: Some customers may comment on ABS activation at low speeds, usually below 8 km/h (5 mph). Upon investigation, the technician will find no DTCs set.
Cause The cause of this condition may be an increased air gap between the wheel speed sensor and the hub reluctor ring due to rust and debris built up on the sensor mounting surface.
Correction Measure AC voltage and clean the wheel speed sensor mounting surfaces.
Raise and support the vehicle. Disconnect both the front wheel speed sensor (WSS) connectors at the frame and harness. Place a Digital Volt Meter (DVM) across the terminals of each WSS connector. Rotate the wheel clockwise approximately one revolution per second. The minimum reading should be at least 350 ACmV's. If the reading is less than 350 ACmV's, remove the wheel speed sensor. Refer to the applicable Wheel Speed Sensor Replacement procedure in the ABS sub-section of the Service Manual. Plug the WSS bore in order to prevent debris from falling into the hub during service. Clean the WSS mounting surface on the hub to remove any rust or corrosion using a wire brush, or equivalent.
Important Make sure that the sensor sits flat on the hub. Check the sensor flange against a straight edge to ensure flatness. If the sensor flange is distorted, replace the sensor.
Apply a thin layer of bearing grease to the hub surface and sensor O-ring prior to sensor installation. Use ONLY Wheel Bearing Lubricant, P/N 01051344. Install either the original sensor or a new one in the hub. Ensure that the sensor is seated flush against the hub. Refer to the applicable Wheel Speed Sensor Replacement procedure in the ABS sub-section of the Service Manual. Place the DVM across the sensor terminals and recheck the voltage while rotating the wheel. The voltage should now read at least 350 ACmV's.
You probably have a bad wheel speed sensor, Most likely the sensor is telling your antilock system to activate, causing your brake pedal to pulse under your foot, you may have to take it and get it diagnosed. or check the wiring harness's, make sure they are properly connected, behind the front brake caliper if your vehicle is equiped with 4 wheel antilock, and the rear antilock may be either behind your brake drum or caliper, depending on disc or drum brakes on the rear. Some Vehichles have a single speed sensor located usually near the center of your rear axle,instead of individual sensors on the rear. look for a wiring harness connecting to the rear axle. It will likely be the only wiring connected into your rear axle. Hope this helps
i would suspect your antilock brakes are activating. you probably have one of your wheel speed sensors that drop to 0 mph fooling the computer that one of the wheels have locked up and therefore goes into antilock mode. no code would set as this is a normal function of antilock brakes, you would need to get a scanner on the car and monitor wheel speed input. as you come to a stop monitor the wheel speeds closely and look to see which one is droppind to 0 prematurly.
You most likely have a wheel speed sensor dropping out this would make abs system think one wheel is locking up and therefore activate. this usually will happen rt before you stop at around 5mph or so.Also if you have bigger tires than factory and have not had abs programmed for this size it can aggravate it
The most likely cause is rust buildup under wheel speed sensors causing them to dislodge(lift up) from front hubs and read incorrectly. If recall has been performed to fix this problem...You may have to replace the appropriate hub in order to stop the ABS activation at low speeds. Let me know if i can help more.