02 Chevy trailblazer

Your vehicle, like any other, should have 4 wheel speed sensors (ABS), that's one per wheel. There are some older vehicles that have only two, which covers the rear wheels - because that's how the system is designed for those vehicles. Unsure of the cost, however, yet I can reference you to my experience with a previous vehicle I owned (2008 Chrysler 300 Touring). They were $179 each - dealer installed. O'Reilly may be able to do a little better, but I don't know since I trust no one with my vehicle besides the dealer. My experience has always been better, and dollar for dollar, the expense isn't much different. For me, it's about "warranty" much more so than cost. Best wishes.

I have a 2005 trailblazer. My ABS light is on. I just did the rear pads and rotors and I was looking for rear sensors and it doesn't have rear speed sensors. The front sensors are included in the wheel bearings i just replaced. Thinking one has gone bad now. They're about 20 bucks each at advance auto parts