What year and model of 4Runner?
Some of the early ABS units on 4Runners (2001-2002 3rd Gens and 2003-2004 4th Gens) didn't like having the battery disconnected, scantool hooked up to it, DTCs cleared, or really just looking at it funny. Doing so would corrupt the Zero Point Calibration data and set a DTC and the warning lights.
As you mentioned, another possibility is a stretched ABS wire and/or something you left unplugged? But without getting a DTC from the ABS system or having a better idea of what vehicle you're working on, I am just shooting from the hip.
Post Note- Do you mean "Brake Light" as in the BRAKE warning lamp, or just the ABS/VRAC/TRAC warning lights?