I just finished testing the wheel speed sensors....I also had the left front rotor and brakes removed. Rotor needed a good beating by the way to get 'er off. In any event got everything put back together and now the abs light comes on only after I start moving forward.......Any ideas ?

 

further notes :

The abs light clears itself after shutting off the truck and starting it back up, but as soon as I start moving the abs light comes back on, either forward or reverse.

 

when you start the truck, the ABS light is off at stand still. that meams the circuit is complete, the sensors are plugged in. as you start moving, the sensor must give an output to the computer. it is not doing that, so the light comes on. sensor is not in the hole or not seeing the turning geara inside. the sensor is however, plugged in correctly to the connector.

 

if you get someone to read the code, it will tell you which sensor is bad. did this start happening after you pulled the sensors, or is that WHY you pulled the sensor?

 

It all started a few months ago when my abs brakes would kick in at low speed braking. I can't remember if the abs light would come on or not while this was happening. I simply pulled the fuse and left it.

But now I trying to figure out what the issue is. After reading several topics on them (abs/speed sensors) I read somewhere that you can test the sensors for ohms so I just went ahead and gave it a shot and those were the reading I got. I pulled the lest side caliper off because I was getting a little squeal at very slow speeds also and to actually have a look at the sensor and stuff. Cleaned off the rotor and the squeal is gone now but now I get the abs light.

I did pull the sensor out from the hub to have a look at it and simply put it back in.

I thought that maybe if a sensor wasn't giving off any ohm readings it might be bad ? I really don't know.

 

I had the same problem and I replaced the rear speed sensor. Didnt fix it. But I read somewhere( I dont know if its true) that if your taillights are burnt out it can set the abs light off. I just put led taillights in before the problem started. And once I switch them back to regular bulbs I havent had the problem since.
seems like a coincidence but it works fine for now.

 

The system is designed as a differential detection.
Both sensors must put out the same signal within a small tolerance limit as a means to detect when one or both wheels lock up as compared to another speed reference so it can detect the condition by comparing..
This signals the Brake control unit to go into a pulsing mode for improved tire to road grip and shorter stopping distance.
If the ABS comes on after moving, one side is still open or not sensing rotation cleanly with a pulse train signal to the control unit.
It then becomes a false signal indicating a sensor signal fault and may even cause the ABS unit to come into action.