GMC Repair: ABS/Service engine light illuminating, gmc yukon, yukon xl

Question
There are no problems with the driving of my 2001 GMC Yukon 2500 Yukon XL w/ 4WD, but recently, the ABS light and Service engine lights started to come on intermittenly and now have been staying on steady. Initially, if I stopped and shut the engine off, they would go out, but would come on again further down the road. Now, they are staying on whenever I run the vehicle. Could it be my ABS sensora are bad and do I only have to on the front tires and how would I replace them? Thanks for your time and advice.

V/R
Rich Hanley

Answer
if you can get the vehicle scanned for the fault codes that could tell you more about whether or not it is the sensors, could be a faulty EBCM.   If it is the sensors you would need to remove the front tires and brake calipers and rotors to access the sensors, they are bolted into the knuckle with allen bolts.  The new ones will come with new harnesses as well.  If you do replace the sensors make sure to thoroughly clean the knuckle to sensor mounting surface of any corrosion or rust.