ABS light on 2000 Nissan Xterra

My wife started and left home and noticed the ABS light was on, what should I have her check first. I told her to make sure there was brake fluid in the reservoir, if that is good where should I look next?

Asked by for the 2000 Nissan Xterra
The ABS light indicates that the computer has detected a malfunction in the ABS system and has diagnostic codes and data stored which would be essential in diagnosing the problem.
A technician with a scanner can access the diagnostic codes and data and then be able to give you a diagnosis.
It may not be a matter of low brake fluid. Get it checked by a Nissan specialist ASAP, brakes are a safety issue.
FYI, when the warning light's on, the ABS system is inoperative, though the conventional brake system may still be functional.
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