Snap on scanners are capable of reading these codes, but they have to have the appropriate software modules. If your traction and ABS lights are on, there will be codes, which leads me to believe the scanner used is not capable of reading them.
I'm not sure if your 97 has active steering control, but on my 01 the problem can be a steering wheel position sensor, yaw sensor, wheel speed sensors, the EBCM (electronic brake control module), etc. Most of the time on our cars its the wheel speed sensor, which is fixed by replacing the bearing/hub, but on my car it was the EBCM.
Get the car scanned with a system capable of reading these codes.
In the meantime, pull the electrical connectors off the wheel speed sensors, make sure the connection is clean and dry, add some dielectric grease, and put them back on. You may get lucky. Also, trace the wires going to the wheel speed sensors as far back as you can, and look for them rubbing on metal and possibly wearing through the insulation and grounding out.
2001 Bonneville SSEi (retired at 365,000 Kms.)
2014 Jeep Grand Cherokee Overland (yes, I know its not a GM)