My 2006 Chevy Uplander LS keeps displaying a "service Traction control system, service stability system, service ABS system" message off and on. In addition, we are hearing a squealing noise coming from the front drivers wheel. Mechanic got error code to replace sensor in bearing on the right front wheel(bearing and sensor replaced), which has been done twice. The cover plate over the rotor has been adjusted as apparently this is where the squealing noise came from. Works for a while and then the messages appear and the squealing starts again!! Any ideas what could be wrong?

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For strange error messages like that you need an auto-electrician with a pro grade scan tool computer to find out which is the modules and sensors has failed and is reporting wrongly. A standard code reader isn't bi-directional and can't do this. If the vehicle is driving fine, you can just ignore it.

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Check your wheel speed sensors for proper operation and for metallic debris, make sure your reluctor ring is in working order and not damaged, if all that appears to be in order, then check it with a diagnostic computer. usually it is a failed WSS (wheel speed sensor) if it is part of a wheel bearing assembly then it is possible you have a failed or failing wheel bearing

That's where the ABS pump is, so yes. Get the trouble codes read before you replace anything

when you do the pads you will notice wires coming out of the front hubs clean up the plug ins .. its for the abs if the contacts get dirty your lights come on . start here other wise it can get complicated. do the same at rear i dont know if you have rear disc brakes you may not ??

Your vehicle has electric power steering !
The Electric Power Steering (EPS) system reduces the amount of effort needed to steer the vehicle. The system uses the power steering control module (PSCM), torque sensor, power steering motor rotational sensor, power steering motor, discrete battery voltage supply circuit, and the GMLAN serial data circuit to perform the system functions. The PSCM and power steering motor are each serviced separately from the steering column assembly. However, the motor rotational sensor is serviced as part of the power steering motor, and the torque sensor is serviced as part of the steering column assembly. The PSCM also monitors vehicle speed from the engine control module (ECM) via the GMLAN serial data circuit. At low speeds more assist is provided for easy turning during parking maneuvers. At higher speeds less assist is provided for improved road feel and directional stability.
Stability System Indicator The IPC illuminates the stability system caution indicator when one or more of the following conditions exists. The EBCM sets any one of many VSES-disabling DTCs. The EBCM sends a serial data message to the IPC requesting illumination.
Traction Control System Indicator
TRAC OFF The instrument panel cluster (IPC) illuminates the TRAC OFF indicator when the following occurs:
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The electronic brake control module (EBCM) inhibits the traction control system due to a malfunction in the traction control system. The IPC receives a serial data message from the EBCM requesting illumination.

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The Body Control module (BCM) detects that the traction control switch has been pressed (signal circuit is low). The Body Control module (BCM) sends a serial data message to the EBCM in order to disable traction control. The IPC receives a serial data message from the EBCM requesting illumination. The BCM sends a serial data message to the radio in order to activate an audible warning.

Your best bet is to take it to a ASE certified an qualified repair shop ,that has the diagnostic tool to fix this problem .

if the abs light comes on then there is a code in the abs module to direct you to the problem. find out the code first, then start digging to find the source of the problem. as intermittent as it is it does sound like an internal module problem,but it will set a code in memory if it is the case.

replace/test the trac control sensor

• An internal fault within the yaw rate sensor/lateral accelerometer, P/N 15189628, may be the first possible cause. • The vehicle stability enhancement system (VSES) electronic brake traction control module See if this info helps

Anything a/c related is best left to a mechanic. You prob have a freon leak somewhere. Try adding a can or 2 to see if that works.
As far as the other lights, they prob just need their recommended servicing.