Intermittently, on our 2000 Impala LS the Traction Control light will come on and the front wheels begin to "knock"..... it does not happen often. I have replaced the wheel bearings and checked the ABS wires. What else should I look at, it does not happen often, but occasionally.

Traction control comes on, whenever one drive wheel starts to slip.......for example, suppose you come to a stop......and your right wheel is near the curb where dirt may be present, while the left wheel is on dry pavement.....then you accelerate hard, and that right wheel slips and you hear the ABS activating......THAT IS NORMAL........

There are other things that can cause this to happen also......bad tires for example......say one front tire is old/worn, and the other one is newer because it was replaced(cut, had a flat, etc.)......that old tire will have more of a tendency to slip under acceleration than the other one, which will activated the TC system.....

A bad sensor or wiring harness, can cause the same thing to happen, but it usually sets and ABS code , also....

I agree with Tech II

It "knock"'* . . .

- . . . under accelleration/braking/neither/both?
- . . . from a dead stop or at speed or . . . ?
- . . . surface is pavement and clean and dry or . . . ?

I "assumed" the knocking sound he was referring to was the sound made when the ABS/Traction system activates....

Totally understand and agree, but just wanted to make sure the OP hears the "knock" happen when it should happen for a TCS event.