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I am having problems with my abs system, connected a scan tool and found a code for left front wheel speed sensor signal missing. Checked connections and found them to be tight and clean. With the scan tool still connected i had a friend of mine drive and I pulled up the data stream and when braking occurs around 10 to 12 miles an hour the left front sensor shows the minimal value of 3 when the other two match and show their particular value at that time. When the truck is at a stand still all three show 3 as their value. On acceleration and coasting all sensors correspond but once you brake and the truck's speed hits about 10-12 mph left front wheel speed sensor drops of and shows 3 as its value again and actuates the abs system. The ball joints were just done and this started directly after. Before throwing a wheel speed sensor on the truck or digging deeper I am wondering if anyone has seen this problem before. I am also wondering why this is only happening during braking. Perhaps loose or broken wire or could the sensor not be close enough to the tone wheel. I have not ohm'd the sensor wires yet for continuity. Any advise would help. I have the fuse for the abs pulled until l can figure this out.
 

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Check all the wires close for cracks. It is possible that the speed sensor is bad. Is your hub still good? Jack up the front of the truck & try to rock the tire at 12 & 6 o'clock. If there is movement, you have a bad hub/wheel bearing. Its an easy fix.

I have also read where people have pulled the sensor out, cleaned it, & reinstalled.
 

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Sounds like you were getting unwanted ABS activation just before coming to a complete stop? If so and your left speed signal readings were good over said 10mph, I would say check for rust build up under the wheel speed sensor. On the wheel bearing itself. It doesnt take much to push the sensor away just far enough to loose signal at low speeds. You can test the sensor output using a volt meter set on AC volts. Measure the AC voltage of the speed sensor unplugged while turning the wheel or hub by hand. Approx 1 turn per second needs to read at least 350 millivolts AC or higher. Compare both sides, you should see lower voltage output on your problem side. Be careful in removing the sensor to clean the hub surface, it is plastic and can crack or may be allready. Have you checked if your trucks had the ABS sensor cleaning recall done already? If its still open its a free fix including sensors if needed. Hope this helped. P.S. Please fill in your sig so we know something about your truck like at least what year it is.
 
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