1997 Subaru Outback ABS & Check Engine Lights

You have two different computers involved and it's really hard to believe neither one has a fault code. Mechanics always seem to jump on the computer when they don't know what else to do. In both cases the computers detected a problem, set a fault code, and turned the light on to tell you. In the case of the Anti-lock Brake Computer, it also turned the system off. It is possible to have no fault code if one of its fuses is blown. There's always a second circuit to run the warning light, so if there are no codes in that one, check for a blown fuse.

Also have the charging system tested for full-load output current and "ripple" voltage. If ripple voltage is high and output current is one third of what it should be, the generator has a defective diode. 30 amps from the common 90 amp generator is not enough to run the entire electrical system under all conditions. The battery will have to make up the difference until it slowly runs down. Some computers, like the Anti-lock Brake Computer, need a lot of current to run their systems, and they can't do that with low system voltage.