Abs activates just before truck stops (2005 chevy silverado) wheels not skidding, assuming a wheel sensor is bad, how do find out which one, or is the problem in the abs computer, abs light does not come on

This is a condition known as over active ABS. GM has a technical service bulletin for this. Basically what it say is to remove the front wheel speed sensors from the hubs, clean the mating surface between the sensor and the hub, apply some di-electric grease over the cleaned area, and reinstall the sensor.

You can try this on the front sensors and see if the problem goes away. I will warn you that you need to be very careful removing the sensor from the hub as they can break off. If it breaks off in the hub you will need to replace the hub and bearing.

You can also check to see if one of the front wheel bearings is loose. with the tire off the ground grab the tire at the 12 and 6 position and push/pull. if the wheel moves and you can see the rotor moving also than the wheel bearing may be sloppy enough for internal exciter ring to get an excessive gap from the abs sensor.

The easiest thing to do is look at wheel speed data on a higher end scan tool. When the symptom happens you will see the wheel speed drop out. Whatever wheel drops out is the wheel that needs to be checked.

Hope that helps.

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