You have to have the codes read to know the possible causes.
your abs sensor light is on probably becuase the abs in one or all of your breaks are not working, take it to a mechanic so they can tell you if that is for sure the problem.
a computarized test will tell the mechanic why that light is on. You can turn off that light with the computer but if the problem is not corrected it will go back on soon after turning the engine on.
there are many many things that can turn that light on. Fluid levels, bad sensor, etc. When this light comes on it sends a trouble code to the computer. Take it to a mechanic that has a scan tool they can pull the code and tell you what it means.
The check engine light will illuminate if you have a bad O2 sensor. The code set will lead you to the faulty sensor.
Your MIL ( malfunction indicator light ) will be lit and a code for your O2 sensor will be logged.
The check engine light would illuminate and the code(s) set would lead you to which O2 sensor is at fault or why the sensor set the code.
The warning lights on the dashboard of the 1998 Toyota Avalon are designed to tell you if your oil is low, if your gas is low, and if the engine temperature is too high. These lights help you to establish when the vehicle needs to be serviced.
If your vehicle has a bad sensor the check engine light will come on. Otherwise they should be replaced as recommended by your service manual.
The check engine light would illuminate and set a code for the bad O2 sensor.
Check ingine light and your gas mileage get worse.
They generally set a trouble code and the check engine light illuminates.
I can't tell you what it does, but I can tell you it is a pretty easy fix. I believe the part is in the 10-20 dollar range. The sensor is located on the driver's side rear portion of the transmission. Take it out with a 1 inch wrench (some fluid will run out of the hole. I replaced the sensor the first time the check engine light came on, however the sensor is magnetic and collects any ferrous debris in the transmission fluid, and simply cleaning it with a rag worked on subsequent occasions.