This problem only happens with '03-'04 4runner.
If this is a ScanGauge you need to force it to read in ISO mode. Instructions are in the booklet that comes with it. The ABS computer and Yaw rate /Accel sensors go wacky when SG communicates using newer OBD protocol.
Force it into ISO mode then switch everything off, unplug the cable at the back/side of the SG , turn car on and plug cable back in. If it's still blinking you need to do Zero-Point calibration to reset yaw rate / accel sensors back to zero. Lots of info on here about that.
You should be good to go after that. Just remember you have to force ISO mode anytime you disconnect the Scanguage.