I took my 90 4Runner to the dealership becuase the Rear ABS light has been on for a few months and braking has been terrible. They did a diagnostic and said they would have to do another diagnostic after i replace my ABS relay which could be the only problem. The relay is $52.96, Is there any other place I can get the relay for cheaper and is it easy to install becuase dealership is always alot more. Where is it even located under the dash, hood??

 

Have you tried to clean the contacts/sensors on the axels. I am not sure of the location on a 2nd gen. I had my ABS light come on and after cleaning the contacts (easy to remove and wipe) on each axel the light went away and the ABS functions (normally as far as I can tell).
Good luck

 

where are they located on the axles?

 

[[braking has been terrible.]]
Non-functioning ABS will have no effect whatsoever on your normal braking. ABS is designed that way.

It's just rear ABS right? (MY 90 is rear only) On top of the rear axle there is a rubber plug stuck in the third member. Remove the bolt and pull out the plug (that's the sensor.) Shouldn't need cleaned, but why not? Push it back in as tight as you can get it, replace the bolt. Then go to your right front fenderwell and look below the washer bottle and find the connection for the ABS valves and clean it and make sure it's secure.

The ABS ECU is behing the glove box and the relay is located here:

 

Here's the speed sensor. It's a magnetic pickup that reads the teeth on the ring gear as they pass by.

 

so clean everything you mentioned? , Thanks I found the relay. I guess I must have some really warped rotors then. The ABS is rear only on mine too...

 

"I guess I must have some really warped rotors then" that is very likely. Does you steering wheel move/shake while you are braking? Lots of people have issues with warped brakes making the truck pulsate while braking