99 Astro Cargo ABS

1999 Astro ABS kicks in during normal stops. A rotted rear brake line was recently replaced and new front rotors and pads installed. There's no evidence of leakage along the lines or at the master cyl. Ideas?? Thanks, in advance.

You've got a wheel speed sensor that is dropping out at low speeds. Probably one of the fronts since work was recently done there. Easy enough to check: Disconnect the wheel speed sensor connector. Put a meter across the 2 leads. You should get a pretty steady 300mv or so from each sensor when the wheel is spun by hand. Left to right voltage should match pretty closely.

If the ABS unit runs dry, as yours did when the line failed, an ABS capable scan tool MUST be used to bleed the system. If you bleed the system without using the scan tool, you cannot bleed all of the air out of the ABS unit.