You need a code reader with ABS abilities. If you don't have one, perhaps your friends do. My code reader does not have that capability, so I borrowed one and found the problem right away (passenger side rear wheel speed sensor) on my van. This narrowed the problem, which I quickly found to be an unplugged harness.
The code reader would help you locate the problem, which may be one of your wheels.
On these vehicles, it could also be a ground problem - I seem to recall one ground being under the driver's feet on the underside of the vehicle, it tends to get corrosion there and cause problems.
Can you get a code reader that reads ABS?