I was having the Traction Control and ABS light coming on in my '07 HHR, mostly during the intial start up. sometimes the lights would go out, sometimes not. There was no pattern.
I solved the problem by re-routing the wheel speed sensor wiring near the left strut, it appeared to be tight and could tighten more in a turn. Second, I bled the front calipers quite a bit.
Between those 2 actions I have not seen either light come on in 2 months, before it was on several times a week.

 

Thanks for posting. Have had an occasional ESC light after unparking from a tight spot, suspected wires or a connector, will take a look.

 

I ended up replacing the left hub in order to correct the MIL issue. Either the sensor or the wiring was bad. I replaced the hub instead of just the sensor due to the miles, 181,000. It was easy to replace, so I did the right side, too.

 

Did you find that the sensor is not available? I'm pretty sure they aren't available separately.
The pic looks like the wires are compromised at the connector.
You should replace the hubs in pairs to save yourself a little time.